1 //===- ScalarEvolution.cpp - Scalar Evolution Analysis --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the implementation of the scalar evolution analysis
11 // engine, which is used primarily to analyze expressions involving induction
12 // variables in loops.
14 // There are several aspects to this library. First is the representation of
15 // scalar expressions, which are represented as subclasses of the SCEV class.
16 // These classes are used to represent certain types of subexpressions that we
17 // can handle. We only create one SCEV of a particular shape, so
18 // pointer-comparisons for equality are legal.
20 // One important aspect of the SCEV objects is that they are never cyclic, even
21 // if there is a cycle in the dataflow for an expression (ie, a PHI node). If
22 // the PHI node is one of the idioms that we can represent (e.g., a polynomial
23 // recurrence) then we represent it directly as a recurrence node, otherwise we
24 // represent it as a SCEVUnknown node.
26 // In addition to being able to represent expressions of various types, we also
27 // have folders that are used to build the *canonical* representation for a
28 // particular expression. These folders are capable of using a variety of
29 // rewrite rules to simplify the expressions.
31 // Once the folders are defined, we can implement the more interesting
32 // higher-level code, such as the code that recognizes PHI nodes of various
33 // types, computes the execution count of a loop, etc.
35 // TODO: We should use these routines and value representations to implement
36 // dependence analysis!
38 //===----------------------------------------------------------------------===//
40 // There are several good references for the techniques used in this analysis.
42 // Chains of recurrences -- a method to expedite the evaluation
43 // of closed-form functions
44 // Olaf Bachmann, Paul S. Wang, Eugene V. Zima
46 // On computational properties of chains of recurrences
49 // Symbolic Evaluation of Chains of Recurrences for Loop Optimization
50 // Robert A. van Engelen
52 // Efficient Symbolic Analysis for Optimizing Compilers
53 // Robert A. van Engelen
55 // Using the chains of recurrences algebra for data dependence testing and
56 // induction variable substitution
57 // MS Thesis, Johnie Birch
59 //===----------------------------------------------------------------------===//
61 #include "llvm/Analysis/ScalarEvolution.h"
62 #include "llvm/ADT/Optional.h"
63 #include "llvm/ADT/STLExtras.h"
64 #include "llvm/ADT/ScopeExit.h"
65 #include "llvm/ADT/Sequence.h"
66 #include "llvm/ADT/SmallPtrSet.h"
67 #include "llvm/ADT/Statistic.h"
68 #include "llvm/Analysis/AssumptionCache.h"
69 #include "llvm/Analysis/ConstantFolding.h"
70 #include "llvm/Analysis/InstructionSimplify.h"
71 #include "llvm/Analysis/LoopInfo.h"
72 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
73 #include "llvm/Analysis/TargetLibraryInfo.h"
74 #include "llvm/Analysis/ValueTracking.h"
75 #include "llvm/IR/ConstantRange.h"
76 #include "llvm/IR/Constants.h"
77 #include "llvm/IR/DataLayout.h"
78 #include "llvm/IR/DerivedTypes.h"
79 #include "llvm/IR/Dominators.h"
80 #include "llvm/IR/GetElementPtrTypeIterator.h"
81 #include "llvm/IR/GlobalAlias.h"
82 #include "llvm/IR/GlobalVariable.h"
83 #include "llvm/IR/InstIterator.h"
84 #include "llvm/IR/Instructions.h"
85 #include "llvm/IR/LLVMContext.h"
86 #include "llvm/IR/Metadata.h"
87 #include "llvm/IR/Operator.h"
88 #include "llvm/IR/PatternMatch.h"
89 #include "llvm/Support/CommandLine.h"
90 #include "llvm/Support/Debug.h"
91 #include "llvm/Support/ErrorHandling.h"
92 #include "llvm/Support/MathExtras.h"
93 #include "llvm/Support/raw_ostream.h"
94 #include "llvm/Support/SaveAndRestore.h"
98 #define DEBUG_TYPE "scalar-evolution"
100 STATISTIC(NumArrayLenItCounts,
101 "Number of trip counts computed with array length");
102 STATISTIC(NumTripCountsComputed,
103 "Number of loops with predictable loop counts");
104 STATISTIC(NumTripCountsNotComputed,
105 "Number of loops without predictable loop counts");
106 STATISTIC(NumBruteForceTripCountsComputed,
107 "Number of loops with trip counts computed by force");
109 static cl::opt<unsigned>
110 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
111 cl::desc("Maximum number of iterations SCEV will "
112 "symbolically execute a constant "
116 // FIXME: Enable this with EXPENSIVE_CHECKS when the test suite is clean.
118 VerifySCEV("verify-scev",
119 cl::desc("Verify ScalarEvolution's backedge taken counts (slow)"));
121 VerifySCEVMap("verify-scev-maps",
122 cl::desc("Verify no dangling value in ScalarEvolution's "
123 "ExprValueMap (slow)"));
125 static cl::opt<unsigned> MulOpsInlineThreshold(
126 "scev-mulops-inline-threshold", cl::Hidden,
127 cl::desc("Threshold for inlining multiplication operands into a SCEV"),
130 static cl::opt<unsigned> AddOpsInlineThreshold(
131 "scev-addops-inline-threshold", cl::Hidden,
132 cl::desc("Threshold for inlining multiplication operands into a SCEV"),
135 static cl::opt<unsigned> MaxSCEVCompareDepth(
136 "scalar-evolution-max-scev-compare-depth", cl::Hidden,
137 cl::desc("Maximum depth of recursive SCEV complexity comparisons"),
140 static cl::opt<unsigned> MaxSCEVOperationsImplicationDepth(
141 "scalar-evolution-max-scev-operations-implication-depth", cl::Hidden,
142 cl::desc("Maximum depth of recursive SCEV operations implication analysis"),
145 static cl::opt<unsigned> MaxValueCompareDepth(
146 "scalar-evolution-max-value-compare-depth", cl::Hidden,
147 cl::desc("Maximum depth of recursive value complexity comparisons"),
150 static cl::opt<unsigned>
151 MaxAddExprDepth("scalar-evolution-max-addexpr-depth", cl::Hidden,
152 cl::desc("Maximum depth of recursive AddExpr"),
155 static cl::opt<unsigned> MaxConstantEvolvingDepth(
156 "scalar-evolution-max-constant-evolving-depth", cl::Hidden,
157 cl::desc("Maximum depth of recursive constant evolving"), cl::init(32));
159 //===----------------------------------------------------------------------===//
160 // SCEV class definitions
161 //===----------------------------------------------------------------------===//
163 //===----------------------------------------------------------------------===//
164 // Implementation of the SCEV class.
167 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
168 LLVM_DUMP_METHOD void SCEV::dump() const {
174 void SCEV::print(raw_ostream &OS) const {
175 switch (static_cast<SCEVTypes>(getSCEVType())) {
177 cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
180 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
181 const SCEV *Op = Trunc->getOperand();
182 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
183 << *Trunc->getType() << ")";
187 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
188 const SCEV *Op = ZExt->getOperand();
189 OS << "(zext " << *Op->getType() << " " << *Op << " to "
190 << *ZExt->getType() << ")";
194 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
195 const SCEV *Op = SExt->getOperand();
196 OS << "(sext " << *Op->getType() << " " << *Op << " to "
197 << *SExt->getType() << ")";
201 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
202 OS << "{" << *AR->getOperand(0);
203 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
204 OS << ",+," << *AR->getOperand(i);
206 if (AR->hasNoUnsignedWrap())
208 if (AR->hasNoSignedWrap())
210 if (AR->hasNoSelfWrap() &&
211 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
213 AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
221 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
222 const char *OpStr = nullptr;
223 switch (NAry->getSCEVType()) {
224 case scAddExpr: OpStr = " + "; break;
225 case scMulExpr: OpStr = " * "; break;
226 case scUMaxExpr: OpStr = " umax "; break;
227 case scSMaxExpr: OpStr = " smax "; break;
230 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
233 if (std::next(I) != E)
237 switch (NAry->getSCEVType()) {
240 if (NAry->hasNoUnsignedWrap())
242 if (NAry->hasNoSignedWrap())
248 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
249 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
253 const SCEVUnknown *U = cast<SCEVUnknown>(this);
255 if (U->isSizeOf(AllocTy)) {
256 OS << "sizeof(" << *AllocTy << ")";
259 if (U->isAlignOf(AllocTy)) {
260 OS << "alignof(" << *AllocTy << ")";
266 if (U->isOffsetOf(CTy, FieldNo)) {
267 OS << "offsetof(" << *CTy << ", ";
268 FieldNo->printAsOperand(OS, false);
273 // Otherwise just print it normally.
274 U->getValue()->printAsOperand(OS, false);
277 case scCouldNotCompute:
278 OS << "***COULDNOTCOMPUTE***";
281 llvm_unreachable("Unknown SCEV kind!");
284 Type *SCEV::getType() const {
285 switch (static_cast<SCEVTypes>(getSCEVType())) {
287 return cast<SCEVConstant>(this)->getType();
291 return cast<SCEVCastExpr>(this)->getType();
296 return cast<SCEVNAryExpr>(this)->getType();
298 return cast<SCEVAddExpr>(this)->getType();
300 return cast<SCEVUDivExpr>(this)->getType();
302 return cast<SCEVUnknown>(this)->getType();
303 case scCouldNotCompute:
304 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
306 llvm_unreachable("Unknown SCEV kind!");
309 bool SCEV::isZero() const {
310 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
311 return SC->getValue()->isZero();
315 bool SCEV::isOne() const {
316 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
317 return SC->getValue()->isOne();
321 bool SCEV::isAllOnesValue() const {
322 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
323 return SC->getValue()->isAllOnesValue();
327 bool SCEV::isNonConstantNegative() const {
328 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
329 if (!Mul) return false;
331 // If there is a constant factor, it will be first.
332 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
333 if (!SC) return false;
335 // Return true if the value is negative, this matches things like (-42 * V).
336 return SC->getAPInt().isNegative();
339 SCEVCouldNotCompute::SCEVCouldNotCompute() :
340 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
342 bool SCEVCouldNotCompute::classof(const SCEV *S) {
343 return S->getSCEVType() == scCouldNotCompute;
346 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
348 ID.AddInteger(scConstant);
351 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
352 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
353 UniqueSCEVs.InsertNode(S, IP);
357 const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
358 return getConstant(ConstantInt::get(getContext(), Val));
362 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
363 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
364 return getConstant(ConstantInt::get(ITy, V, isSigned));
367 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
368 unsigned SCEVTy, const SCEV *op, Type *ty)
369 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
371 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
372 const SCEV *op, Type *ty)
373 : SCEVCastExpr(ID, scTruncate, op, ty) {
374 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
375 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
376 "Cannot truncate non-integer value!");
379 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
380 const SCEV *op, Type *ty)
381 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
382 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
383 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
384 "Cannot zero extend non-integer value!");
387 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
388 const SCEV *op, Type *ty)
389 : SCEVCastExpr(ID, scSignExtend, op, ty) {
390 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
391 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
392 "Cannot sign extend non-integer value!");
395 void SCEVUnknown::deleted() {
396 // Clear this SCEVUnknown from various maps.
397 SE->forgetMemoizedResults(this);
399 // Remove this SCEVUnknown from the uniquing map.
400 SE->UniqueSCEVs.RemoveNode(this);
402 // Release the value.
406 void SCEVUnknown::allUsesReplacedWith(Value *New) {
407 // Clear this SCEVUnknown from various maps.
408 SE->forgetMemoizedResults(this);
410 // Remove this SCEVUnknown from the uniquing map.
411 SE->UniqueSCEVs.RemoveNode(this);
413 // Update this SCEVUnknown to point to the new value. This is needed
414 // because there may still be outstanding SCEVs which still point to
419 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
420 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
421 if (VCE->getOpcode() == Instruction::PtrToInt)
422 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
423 if (CE->getOpcode() == Instruction::GetElementPtr &&
424 CE->getOperand(0)->isNullValue() &&
425 CE->getNumOperands() == 2)
426 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
428 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
436 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
437 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
438 if (VCE->getOpcode() == Instruction::PtrToInt)
439 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
440 if (CE->getOpcode() == Instruction::GetElementPtr &&
441 CE->getOperand(0)->isNullValue()) {
443 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
444 if (StructType *STy = dyn_cast<StructType>(Ty))
445 if (!STy->isPacked() &&
446 CE->getNumOperands() == 3 &&
447 CE->getOperand(1)->isNullValue()) {
448 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
450 STy->getNumElements() == 2 &&
451 STy->getElementType(0)->isIntegerTy(1)) {
452 AllocTy = STy->getElementType(1);
461 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
462 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
463 if (VCE->getOpcode() == Instruction::PtrToInt)
464 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
465 if (CE->getOpcode() == Instruction::GetElementPtr &&
466 CE->getNumOperands() == 3 &&
467 CE->getOperand(0)->isNullValue() &&
468 CE->getOperand(1)->isNullValue()) {
470 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
471 // Ignore vector types here so that ScalarEvolutionExpander doesn't
472 // emit getelementptrs that index into vectors.
473 if (Ty->isStructTy() || Ty->isArrayTy()) {
475 FieldNo = CE->getOperand(2);
483 //===----------------------------------------------------------------------===//
485 //===----------------------------------------------------------------------===//
487 /// Compare the two values \p LV and \p RV in terms of their "complexity" where
488 /// "complexity" is a partial (and somewhat ad-hoc) relation used to order
489 /// operands in SCEV expressions. \p EqCache is a set of pairs of values that
490 /// have been previously deemed to be "equally complex" by this routine. It is
491 /// intended to avoid exponential time complexity in cases like:
501 /// CompareValueComplexity(%f, %c)
503 /// Since we do not continue running this routine on expression trees once we
504 /// have seen unequal values, there is no need to track them in the cache.
506 CompareValueComplexity(SmallSet<std::pair<Value *, Value *>, 8> &EqCache,
507 const LoopInfo *const LI, Value *LV, Value *RV,
509 if (Depth > MaxValueCompareDepth || EqCache.count({LV, RV}))
512 // Order pointer values after integer values. This helps SCEVExpander form
514 bool LIsPointer = LV->getType()->isPointerTy(),
515 RIsPointer = RV->getType()->isPointerTy();
516 if (LIsPointer != RIsPointer)
517 return (int)LIsPointer - (int)RIsPointer;
519 // Compare getValueID values.
520 unsigned LID = LV->getValueID(), RID = RV->getValueID();
522 return (int)LID - (int)RID;
524 // Sort arguments by their position.
525 if (const auto *LA = dyn_cast<Argument>(LV)) {
526 const auto *RA = cast<Argument>(RV);
527 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
528 return (int)LArgNo - (int)RArgNo;
531 if (const auto *LGV = dyn_cast<GlobalValue>(LV)) {
532 const auto *RGV = cast<GlobalValue>(RV);
534 const auto IsGVNameSemantic = [&](const GlobalValue *GV) {
535 auto LT = GV->getLinkage();
536 return !(GlobalValue::isPrivateLinkage(LT) ||
537 GlobalValue::isInternalLinkage(LT));
540 // Use the names to distinguish the two values, but only if the
541 // names are semantically important.
542 if (IsGVNameSemantic(LGV) && IsGVNameSemantic(RGV))
543 return LGV->getName().compare(RGV->getName());
546 // For instructions, compare their loop depth, and their operand count. This
548 if (const auto *LInst = dyn_cast<Instruction>(LV)) {
549 const auto *RInst = cast<Instruction>(RV);
551 // Compare loop depths.
552 const BasicBlock *LParent = LInst->getParent(),
553 *RParent = RInst->getParent();
554 if (LParent != RParent) {
555 unsigned LDepth = LI->getLoopDepth(LParent),
556 RDepth = LI->getLoopDepth(RParent);
557 if (LDepth != RDepth)
558 return (int)LDepth - (int)RDepth;
561 // Compare the number of operands.
562 unsigned LNumOps = LInst->getNumOperands(),
563 RNumOps = RInst->getNumOperands();
564 if (LNumOps != RNumOps)
565 return (int)LNumOps - (int)RNumOps;
567 for (unsigned Idx : seq(0u, LNumOps)) {
569 CompareValueComplexity(EqCache, LI, LInst->getOperand(Idx),
570 RInst->getOperand(Idx), Depth + 1);
576 EqCache.insert({LV, RV});
580 // Return negative, zero, or positive, if LHS is less than, equal to, or greater
581 // than RHS, respectively. A three-way result allows recursive comparisons to be
583 static int CompareSCEVComplexity(
584 SmallSet<std::pair<const SCEV *, const SCEV *>, 8> &EqCacheSCEV,
585 const LoopInfo *const LI, const SCEV *LHS, const SCEV *RHS,
586 unsigned Depth = 0) {
587 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
591 // Primarily, sort the SCEVs by their getSCEVType().
592 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
594 return (int)LType - (int)RType;
596 if (Depth > MaxSCEVCompareDepth || EqCacheSCEV.count({LHS, RHS}))
598 // Aside from the getSCEVType() ordering, the particular ordering
599 // isn't very important except that it's beneficial to be consistent,
600 // so that (a + b) and (b + a) don't end up as different expressions.
601 switch (static_cast<SCEVTypes>(LType)) {
603 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
604 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
606 SmallSet<std::pair<Value *, Value *>, 8> EqCache;
607 int X = CompareValueComplexity(EqCache, LI, LU->getValue(), RU->getValue(),
610 EqCacheSCEV.insert({LHS, RHS});
615 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
616 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
618 // Compare constant values.
619 const APInt &LA = LC->getAPInt();
620 const APInt &RA = RC->getAPInt();
621 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
622 if (LBitWidth != RBitWidth)
623 return (int)LBitWidth - (int)RBitWidth;
624 return LA.ult(RA) ? -1 : 1;
628 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
629 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
631 // Compare addrec loop depths.
632 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
633 if (LLoop != RLoop) {
634 unsigned LDepth = LLoop->getLoopDepth(), RDepth = RLoop->getLoopDepth();
635 if (LDepth != RDepth)
636 return (int)LDepth - (int)RDepth;
639 // Addrec complexity grows with operand count.
640 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
641 if (LNumOps != RNumOps)
642 return (int)LNumOps - (int)RNumOps;
644 // Lexicographically compare.
645 for (unsigned i = 0; i != LNumOps; ++i) {
646 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LA->getOperand(i),
647 RA->getOperand(i), Depth + 1);
651 EqCacheSCEV.insert({LHS, RHS});
659 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
660 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
662 // Lexicographically compare n-ary expressions.
663 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
664 if (LNumOps != RNumOps)
665 return (int)LNumOps - (int)RNumOps;
667 for (unsigned i = 0; i != LNumOps; ++i) {
670 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getOperand(i),
671 RC->getOperand(i), Depth + 1);
675 EqCacheSCEV.insert({LHS, RHS});
680 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
681 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
683 // Lexicographically compare udiv expressions.
684 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getLHS(), RC->getLHS(),
688 X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getRHS(), RC->getRHS(),
691 EqCacheSCEV.insert({LHS, RHS});
698 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
699 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
701 // Compare cast expressions by operand.
702 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getOperand(),
703 RC->getOperand(), Depth + 1);
705 EqCacheSCEV.insert({LHS, RHS});
709 case scCouldNotCompute:
710 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
712 llvm_unreachable("Unknown SCEV kind!");
715 /// Given a list of SCEV objects, order them by their complexity, and group
716 /// objects of the same complexity together by value. When this routine is
717 /// finished, we know that any duplicates in the vector are consecutive and that
718 /// complexity is monotonically increasing.
720 /// Note that we go take special precautions to ensure that we get deterministic
721 /// results from this routine. In other words, we don't want the results of
722 /// this to depend on where the addresses of various SCEV objects happened to
725 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
727 if (Ops.size() < 2) return; // Noop
729 SmallSet<std::pair<const SCEV *, const SCEV *>, 8> EqCache;
730 if (Ops.size() == 2) {
731 // This is the common case, which also happens to be trivially simple.
733 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
734 if (CompareSCEVComplexity(EqCache, LI, RHS, LHS) < 0)
739 // Do the rough sort by complexity.
740 std::stable_sort(Ops.begin(), Ops.end(),
741 [&EqCache, LI](const SCEV *LHS, const SCEV *RHS) {
742 return CompareSCEVComplexity(EqCache, LI, LHS, RHS) < 0;
745 // Now that we are sorted by complexity, group elements of the same
746 // complexity. Note that this is, at worst, N^2, but the vector is likely to
747 // be extremely short in practice. Note that we take this approach because we
748 // do not want to depend on the addresses of the objects we are grouping.
749 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
750 const SCEV *S = Ops[i];
751 unsigned Complexity = S->getSCEVType();
753 // If there are any objects of the same complexity and same value as this
755 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
756 if (Ops[j] == S) { // Found a duplicate.
757 // Move it to immediately after i'th element.
758 std::swap(Ops[i+1], Ops[j]);
759 ++i; // no need to rescan it.
760 if (i == e-2) return; // Done!
766 // Returns the size of the SCEV S.
767 static inline int sizeOfSCEV(const SCEV *S) {
768 struct FindSCEVSize {
770 FindSCEVSize() : Size(0) {}
772 bool follow(const SCEV *S) {
774 // Keep looking at all operands of S.
777 bool isDone() const {
783 SCEVTraversal<FindSCEVSize> ST(F);
790 struct SCEVDivision : public SCEVVisitor<SCEVDivision, void> {
792 // Computes the Quotient and Remainder of the division of Numerator by
794 static void divide(ScalarEvolution &SE, const SCEV *Numerator,
795 const SCEV *Denominator, const SCEV **Quotient,
796 const SCEV **Remainder) {
797 assert(Numerator && Denominator && "Uninitialized SCEV");
799 SCEVDivision D(SE, Numerator, Denominator);
801 // Check for the trivial case here to avoid having to check for it in the
803 if (Numerator == Denominator) {
809 if (Numerator->isZero()) {
815 // A simple case when N/1. The quotient is N.
816 if (Denominator->isOne()) {
817 *Quotient = Numerator;
822 // Split the Denominator when it is a product.
823 if (const SCEVMulExpr *T = dyn_cast<SCEVMulExpr>(Denominator)) {
825 *Quotient = Numerator;
826 for (const SCEV *Op : T->operands()) {
827 divide(SE, *Quotient, Op, &Q, &R);
830 // Bail out when the Numerator is not divisible by one of the terms of
834 *Remainder = Numerator;
843 *Quotient = D.Quotient;
844 *Remainder = D.Remainder;
847 // Except in the trivial case described above, we do not know how to divide
848 // Expr by Denominator for the following functions with empty implementation.
849 void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
850 void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
851 void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
852 void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
853 void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
854 void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
855 void visitUnknown(const SCEVUnknown *Numerator) {}
856 void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
858 void visitConstant(const SCEVConstant *Numerator) {
859 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
860 APInt NumeratorVal = Numerator->getAPInt();
861 APInt DenominatorVal = D->getAPInt();
862 uint32_t NumeratorBW = NumeratorVal.getBitWidth();
863 uint32_t DenominatorBW = DenominatorVal.getBitWidth();
865 if (NumeratorBW > DenominatorBW)
866 DenominatorVal = DenominatorVal.sext(NumeratorBW);
867 else if (NumeratorBW < DenominatorBW)
868 NumeratorVal = NumeratorVal.sext(DenominatorBW);
870 APInt QuotientVal(NumeratorVal.getBitWidth(), 0);
871 APInt RemainderVal(NumeratorVal.getBitWidth(), 0);
872 APInt::sdivrem(NumeratorVal, DenominatorVal, QuotientVal, RemainderVal);
873 Quotient = SE.getConstant(QuotientVal);
874 Remainder = SE.getConstant(RemainderVal);
879 void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
880 const SCEV *StartQ, *StartR, *StepQ, *StepR;
881 if (!Numerator->isAffine())
882 return cannotDivide(Numerator);
883 divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
884 divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
885 // Bail out if the types do not match.
886 Type *Ty = Denominator->getType();
887 if (Ty != StartQ->getType() || Ty != StartR->getType() ||
888 Ty != StepQ->getType() || Ty != StepR->getType())
889 return cannotDivide(Numerator);
890 Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
891 Numerator->getNoWrapFlags());
892 Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
893 Numerator->getNoWrapFlags());
896 void visitAddExpr(const SCEVAddExpr *Numerator) {
897 SmallVector<const SCEV *, 2> Qs, Rs;
898 Type *Ty = Denominator->getType();
900 for (const SCEV *Op : Numerator->operands()) {
902 divide(SE, Op, Denominator, &Q, &R);
904 // Bail out if types do not match.
905 if (Ty != Q->getType() || Ty != R->getType())
906 return cannotDivide(Numerator);
912 if (Qs.size() == 1) {
918 Quotient = SE.getAddExpr(Qs);
919 Remainder = SE.getAddExpr(Rs);
922 void visitMulExpr(const SCEVMulExpr *Numerator) {
923 SmallVector<const SCEV *, 2> Qs;
924 Type *Ty = Denominator->getType();
926 bool FoundDenominatorTerm = false;
927 for (const SCEV *Op : Numerator->operands()) {
928 // Bail out if types do not match.
929 if (Ty != Op->getType())
930 return cannotDivide(Numerator);
932 if (FoundDenominatorTerm) {
937 // Check whether Denominator divides one of the product operands.
939 divide(SE, Op, Denominator, &Q, &R);
945 // Bail out if types do not match.
946 if (Ty != Q->getType())
947 return cannotDivide(Numerator);
949 FoundDenominatorTerm = true;
953 if (FoundDenominatorTerm) {
958 Quotient = SE.getMulExpr(Qs);
962 if (!isa<SCEVUnknown>(Denominator))
963 return cannotDivide(Numerator);
965 // The Remainder is obtained by replacing Denominator by 0 in Numerator.
966 ValueToValueMap RewriteMap;
967 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
968 cast<SCEVConstant>(Zero)->getValue();
969 Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
971 if (Remainder->isZero()) {
972 // The Quotient is obtained by replacing Denominator by 1 in Numerator.
973 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
974 cast<SCEVConstant>(One)->getValue();
976 SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
980 // Quotient is (Numerator - Remainder) divided by Denominator.
982 const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
983 // This SCEV does not seem to simplify: fail the division here.
984 if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator))
985 return cannotDivide(Numerator);
986 divide(SE, Diff, Denominator, &Q, &R);
988 return cannotDivide(Numerator);
993 SCEVDivision(ScalarEvolution &S, const SCEV *Numerator,
994 const SCEV *Denominator)
995 : SE(S), Denominator(Denominator) {
996 Zero = SE.getZero(Denominator->getType());
997 One = SE.getOne(Denominator->getType());
999 // We generally do not know how to divide Expr by Denominator. We
1000 // initialize the division to a "cannot divide" state to simplify the rest
1002 cannotDivide(Numerator);
1005 // Convenience function for giving up on the division. We set the quotient to
1006 // be equal to zero and the remainder to be equal to the numerator.
1007 void cannotDivide(const SCEV *Numerator) {
1009 Remainder = Numerator;
1012 ScalarEvolution &SE;
1013 const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
1018 //===----------------------------------------------------------------------===//
1019 // Simple SCEV method implementations
1020 //===----------------------------------------------------------------------===//
1022 /// Compute BC(It, K). The result has width W. Assume, K > 0.
1023 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
1024 ScalarEvolution &SE,
1026 // Handle the simplest case efficiently.
1028 return SE.getTruncateOrZeroExtend(It, ResultTy);
1030 // We are using the following formula for BC(It, K):
1032 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
1034 // Suppose, W is the bitwidth of the return value. We must be prepared for
1035 // overflow. Hence, we must assure that the result of our computation is
1036 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
1037 // safe in modular arithmetic.
1039 // However, this code doesn't use exactly that formula; the formula it uses
1040 // is something like the following, where T is the number of factors of 2 in
1041 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
1044 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
1046 // This formula is trivially equivalent to the previous formula. However,
1047 // this formula can be implemented much more efficiently. The trick is that
1048 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
1049 // arithmetic. To do exact division in modular arithmetic, all we have
1050 // to do is multiply by the inverse. Therefore, this step can be done at
1053 // The next issue is how to safely do the division by 2^T. The way this
1054 // is done is by doing the multiplication step at a width of at least W + T
1055 // bits. This way, the bottom W+T bits of the product are accurate. Then,
1056 // when we perform the division by 2^T (which is equivalent to a right shift
1057 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
1058 // truncated out after the division by 2^T.
1060 // In comparison to just directly using the first formula, this technique
1061 // is much more efficient; using the first formula requires W * K bits,
1062 // but this formula less than W + K bits. Also, the first formula requires
1063 // a division step, whereas this formula only requires multiplies and shifts.
1065 // It doesn't matter whether the subtraction step is done in the calculation
1066 // width or the input iteration count's width; if the subtraction overflows,
1067 // the result must be zero anyway. We prefer here to do it in the width of
1068 // the induction variable because it helps a lot for certain cases; CodeGen
1069 // isn't smart enough to ignore the overflow, which leads to much less
1070 // efficient code if the width of the subtraction is wider than the native
1073 // (It's possible to not widen at all by pulling out factors of 2 before
1074 // the multiplication; for example, K=2 can be calculated as
1075 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
1076 // extra arithmetic, so it's not an obvious win, and it gets
1077 // much more complicated for K > 3.)
1079 // Protection from insane SCEVs; this bound is conservative,
1080 // but it probably doesn't matter.
1082 return SE.getCouldNotCompute();
1084 unsigned W = SE.getTypeSizeInBits(ResultTy);
1086 // Calculate K! / 2^T and T; we divide out the factors of two before
1087 // multiplying for calculating K! / 2^T to avoid overflow.
1088 // Other overflow doesn't matter because we only care about the bottom
1089 // W bits of the result.
1090 APInt OddFactorial(W, 1);
1092 for (unsigned i = 3; i <= K; ++i) {
1094 unsigned TwoFactors = Mult.countTrailingZeros();
1096 Mult.lshrInPlace(TwoFactors);
1097 OddFactorial *= Mult;
1100 // We need at least W + T bits for the multiplication step
1101 unsigned CalculationBits = W + T;
1103 // Calculate 2^T, at width T+W.
1104 APInt DivFactor = APInt::getOneBitSet(CalculationBits, T);
1106 // Calculate the multiplicative inverse of K! / 2^T;
1107 // this multiplication factor will perform the exact division by
1109 APInt Mod = APInt::getSignedMinValue(W+1);
1110 APInt MultiplyFactor = OddFactorial.zext(W+1);
1111 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
1112 MultiplyFactor = MultiplyFactor.trunc(W);
1114 // Calculate the product, at width T+W
1115 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
1117 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
1118 for (unsigned i = 1; i != K; ++i) {
1119 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
1120 Dividend = SE.getMulExpr(Dividend,
1121 SE.getTruncateOrZeroExtend(S, CalculationTy));
1125 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
1127 // Truncate the result, and divide by K! / 2^T.
1129 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
1130 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
1133 /// Return the value of this chain of recurrences at the specified iteration
1134 /// number. We can evaluate this recurrence by multiplying each element in the
1135 /// chain by the binomial coefficient corresponding to it. In other words, we
1136 /// can evaluate {A,+,B,+,C,+,D} as:
1138 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
1140 /// where BC(It, k) stands for binomial coefficient.
1142 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
1143 ScalarEvolution &SE) const {
1144 const SCEV *Result = getStart();
1145 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
1146 // The computation is correct in the face of overflow provided that the
1147 // multiplication is performed _after_ the evaluation of the binomial
1149 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
1150 if (isa<SCEVCouldNotCompute>(Coeff))
1153 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
1158 //===----------------------------------------------------------------------===//
1159 // SCEV Expression folder implementations
1160 //===----------------------------------------------------------------------===//
1162 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
1164 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
1165 "This is not a truncating conversion!");
1166 assert(isSCEVable(Ty) &&
1167 "This is not a conversion to a SCEVable type!");
1168 Ty = getEffectiveSCEVType(Ty);
1170 FoldingSetNodeID ID;
1171 ID.AddInteger(scTruncate);
1175 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1177 // Fold if the operand is constant.
1178 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1180 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
1182 // trunc(trunc(x)) --> trunc(x)
1183 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
1184 return getTruncateExpr(ST->getOperand(), Ty);
1186 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
1187 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1188 return getTruncateOrSignExtend(SS->getOperand(), Ty);
1190 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
1191 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1192 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
1194 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
1195 // eliminate all the truncates, or we replace other casts with truncates.
1196 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
1197 SmallVector<const SCEV *, 4> Operands;
1198 bool hasTrunc = false;
1199 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
1200 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
1201 if (!isa<SCEVCastExpr>(SA->getOperand(i)))
1202 hasTrunc = isa<SCEVTruncateExpr>(S);
1203 Operands.push_back(S);
1206 return getAddExpr(Operands);
1207 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1210 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
1211 // eliminate all the truncates, or we replace other casts with truncates.
1212 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
1213 SmallVector<const SCEV *, 4> Operands;
1214 bool hasTrunc = false;
1215 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
1216 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
1217 if (!isa<SCEVCastExpr>(SM->getOperand(i)))
1218 hasTrunc = isa<SCEVTruncateExpr>(S);
1219 Operands.push_back(S);
1222 return getMulExpr(Operands);
1223 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1226 // If the input value is a chrec scev, truncate the chrec's operands.
1227 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
1228 SmallVector<const SCEV *, 4> Operands;
1229 for (const SCEV *Op : AddRec->operands())
1230 Operands.push_back(getTruncateExpr(Op, Ty));
1231 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
1234 // The cast wasn't folded; create an explicit cast node. We can reuse
1235 // the existing insert position since if we get here, we won't have
1236 // made any changes which would invalidate it.
1237 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
1239 UniqueSCEVs.InsertNode(S, IP);
1243 // Get the limit of a recurrence such that incrementing by Step cannot cause
1244 // signed overflow as long as the value of the recurrence within the
1245 // loop does not exceed this limit before incrementing.
1246 static const SCEV *getSignedOverflowLimitForStep(const SCEV *Step,
1247 ICmpInst::Predicate *Pred,
1248 ScalarEvolution *SE) {
1249 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1250 if (SE->isKnownPositive(Step)) {
1251 *Pred = ICmpInst::ICMP_SLT;
1252 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1253 SE->getSignedRange(Step).getSignedMax());
1255 if (SE->isKnownNegative(Step)) {
1256 *Pred = ICmpInst::ICMP_SGT;
1257 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1258 SE->getSignedRange(Step).getSignedMin());
1263 // Get the limit of a recurrence such that incrementing by Step cannot cause
1264 // unsigned overflow as long as the value of the recurrence within the loop does
1265 // not exceed this limit before incrementing.
1266 static const SCEV *getUnsignedOverflowLimitForStep(const SCEV *Step,
1267 ICmpInst::Predicate *Pred,
1268 ScalarEvolution *SE) {
1269 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1270 *Pred = ICmpInst::ICMP_ULT;
1272 return SE->getConstant(APInt::getMinValue(BitWidth) -
1273 SE->getUnsignedRange(Step).getUnsignedMax());
1278 struct ExtendOpTraitsBase {
1279 typedef const SCEV *(ScalarEvolution::*GetExtendExprTy)(
1280 const SCEV *, Type *, ScalarEvolution::ExtendCacheTy &Cache);
1283 // Used to make code generic over signed and unsigned overflow.
1284 template <typename ExtendOp> struct ExtendOpTraits {
1287 // static const SCEV::NoWrapFlags WrapType;
1289 // static const ExtendOpTraitsBase::GetExtendExprTy GetExtendExpr;
1291 // static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1292 // ICmpInst::Predicate *Pred,
1293 // ScalarEvolution *SE);
1297 struct ExtendOpTraits<SCEVSignExtendExpr> : public ExtendOpTraitsBase {
1298 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNSW;
1300 static const GetExtendExprTy GetExtendExpr;
1302 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1303 ICmpInst::Predicate *Pred,
1304 ScalarEvolution *SE) {
1305 return getSignedOverflowLimitForStep(Step, Pred, SE);
1309 const ExtendOpTraitsBase::GetExtendExprTy
1310 ExtendOpTraits<SCEVSignExtendExpr>::GetExtendExpr =
1311 &ScalarEvolution::getSignExtendExprCached;
1314 struct ExtendOpTraits<SCEVZeroExtendExpr> : public ExtendOpTraitsBase {
1315 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNUW;
1317 static const GetExtendExprTy GetExtendExpr;
1319 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1320 ICmpInst::Predicate *Pred,
1321 ScalarEvolution *SE) {
1322 return getUnsignedOverflowLimitForStep(Step, Pred, SE);
1326 const ExtendOpTraitsBase::GetExtendExprTy
1327 ExtendOpTraits<SCEVZeroExtendExpr>::GetExtendExpr =
1328 &ScalarEvolution::getZeroExtendExprCached;
1331 // The recurrence AR has been shown to have no signed/unsigned wrap or something
1332 // close to it. Typically, if we can prove NSW/NUW for AR, then we can just as
1333 // easily prove NSW/NUW for its preincrement or postincrement sibling. This
1334 // allows normalizing a sign/zero extended AddRec as such: {sext/zext(Step +
1335 // Start),+,Step} => {(Step + sext/zext(Start),+,Step} As a result, the
1336 // expression "Step + sext/zext(PreIncAR)" is congruent with
1337 // "sext/zext(PostIncAR)"
1338 template <typename ExtendOpTy>
1339 static const SCEV *getPreStartForExtend(const SCEVAddRecExpr *AR, Type *Ty,
1340 ScalarEvolution *SE,
1341 ScalarEvolution::ExtendCacheTy &Cache) {
1342 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1343 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1345 const Loop *L = AR->getLoop();
1346 const SCEV *Start = AR->getStart();
1347 const SCEV *Step = AR->getStepRecurrence(*SE);
1349 // Check for a simple looking step prior to loop entry.
1350 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1354 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1355 // subtraction is expensive. For this purpose, perform a quick and dirty
1356 // difference, by checking for Step in the operand list.
1357 SmallVector<const SCEV *, 4> DiffOps;
1358 for (const SCEV *Op : SA->operands())
1360 DiffOps.push_back(Op);
1362 if (DiffOps.size() == SA->getNumOperands())
1365 // Try to prove `WrapType` (SCEV::FlagNSW or SCEV::FlagNUW) on `PreStart` +
1368 // 1. NSW/NUW flags on the step increment.
1369 auto PreStartFlags =
1370 ScalarEvolution::maskFlags(SA->getNoWrapFlags(), SCEV::FlagNUW);
1371 const SCEV *PreStart = SE->getAddExpr(DiffOps, PreStartFlags);
1372 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1373 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1375 // "{S,+,X} is <nsw>/<nuw>" and "the backedge is taken at least once" implies
1376 // "S+X does not sign/unsign-overflow".
1379 const SCEV *BECount = SE->getBackedgeTakenCount(L);
1380 if (PreAR && PreAR->getNoWrapFlags(WrapType) &&
1381 !isa<SCEVCouldNotCompute>(BECount) && SE->isKnownPositive(BECount))
1384 // 2. Direct overflow check on the step operation's expression.
1385 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1386 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1387 const SCEV *OperandExtendedStart =
1388 SE->getAddExpr((SE->*GetExtendExpr)(PreStart, WideTy, Cache),
1389 (SE->*GetExtendExpr)(Step, WideTy, Cache));
1390 if ((SE->*GetExtendExpr)(Start, WideTy, Cache) == OperandExtendedStart) {
1391 if (PreAR && AR->getNoWrapFlags(WrapType)) {
1392 // If we know `AR` == {`PreStart`+`Step`,+,`Step`} is `WrapType` (FlagNSW
1393 // or FlagNUW) and that `PreStart` + `Step` is `WrapType` too, then
1394 // `PreAR` == {`PreStart`,+,`Step`} is also `WrapType`. Cache this fact.
1395 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(WrapType);
1400 // 3. Loop precondition.
1401 ICmpInst::Predicate Pred;
1402 const SCEV *OverflowLimit =
1403 ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(Step, &Pred, SE);
1405 if (OverflowLimit &&
1406 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit))
1412 // Get the normalized zero or sign extended expression for this AddRec's Start.
1413 template <typename ExtendOpTy>
1414 static const SCEV *getExtendAddRecStart(const SCEVAddRecExpr *AR, Type *Ty,
1415 ScalarEvolution *SE,
1416 ScalarEvolution::ExtendCacheTy &Cache) {
1417 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1419 const SCEV *PreStart = getPreStartForExtend<ExtendOpTy>(AR, Ty, SE, Cache);
1421 return (SE->*GetExtendExpr)(AR->getStart(), Ty, Cache);
1423 return SE->getAddExpr(
1424 (SE->*GetExtendExpr)(AR->getStepRecurrence(*SE), Ty, Cache),
1425 (SE->*GetExtendExpr)(PreStart, Ty, Cache));
1428 // Try to prove away overflow by looking at "nearby" add recurrences. A
1429 // motivating example for this rule: if we know `{0,+,4}` is `ult` `-1` and it
1430 // does not itself wrap then we can conclude that `{1,+,4}` is `nuw`.
1434 // {S,+,X} == {S-T,+,X} + T
1435 // => Ext({S,+,X}) == Ext({S-T,+,X} + T)
1437 // If ({S-T,+,X} + T) does not overflow ... (1)
1439 // RHS == Ext({S-T,+,X} + T) == Ext({S-T,+,X}) + Ext(T)
1441 // If {S-T,+,X} does not overflow ... (2)
1443 // RHS == Ext({S-T,+,X}) + Ext(T) == {Ext(S-T),+,Ext(X)} + Ext(T)
1444 // == {Ext(S-T)+Ext(T),+,Ext(X)}
1446 // If (S-T)+T does not overflow ... (3)
1448 // RHS == {Ext(S-T)+Ext(T),+,Ext(X)} == {Ext(S-T+T),+,Ext(X)}
1449 // == {Ext(S),+,Ext(X)} == LHS
1451 // Thus, if (1), (2) and (3) are true for some T, then
1452 // Ext({S,+,X}) == {Ext(S),+,Ext(X)}
1454 // (3) is implied by (1) -- "(S-T)+T does not overflow" is simply "({S-T,+,X}+T)
1455 // does not overflow" restricted to the 0th iteration. Therefore we only need
1456 // to check for (1) and (2).
1458 // In the current context, S is `Start`, X is `Step`, Ext is `ExtendOpTy` and T
1459 // is `Delta` (defined below).
1461 template <typename ExtendOpTy>
1462 bool ScalarEvolution::proveNoWrapByVaryingStart(const SCEV *Start,
1465 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1467 // We restrict `Start` to a constant to prevent SCEV from spending too much
1468 // time here. It is correct (but more expensive) to continue with a
1469 // non-constant `Start` and do a general SCEV subtraction to compute
1470 // `PreStart` below.
1472 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start);
1476 APInt StartAI = StartC->getAPInt();
1478 for (unsigned Delta : {-2, -1, 1, 2}) {
1479 const SCEV *PreStart = getConstant(StartAI - Delta);
1481 FoldingSetNodeID ID;
1482 ID.AddInteger(scAddRecExpr);
1483 ID.AddPointer(PreStart);
1484 ID.AddPointer(Step);
1488 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1490 // Give up if we don't already have the add recurrence we need because
1491 // actually constructing an add recurrence is relatively expensive.
1492 if (PreAR && PreAR->getNoWrapFlags(WrapType)) { // proves (2)
1493 const SCEV *DeltaS = getConstant(StartC->getType(), Delta);
1494 ICmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1495 const SCEV *Limit = ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(
1496 DeltaS, &Pred, this);
1497 if (Limit && isKnownPredicate(Pred, PreAR, Limit)) // proves (1)
1505 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty) {
1506 // Use the local cache to prevent exponential behavior of
1507 // getZeroExtendExprImpl.
1508 ExtendCacheTy Cache;
1509 return getZeroExtendExprCached(Op, Ty, Cache);
1512 /// Query \p Cache before calling getZeroExtendExprImpl. If there is no
1513 /// related entry in the \p Cache, call getZeroExtendExprImpl and save
1514 /// the result in the \p Cache.
1515 const SCEV *ScalarEvolution::getZeroExtendExprCached(const SCEV *Op, Type *Ty,
1516 ExtendCacheTy &Cache) {
1517 auto It = Cache.find({Op, Ty});
1518 if (It != Cache.end())
1520 const SCEV *ZExt = getZeroExtendExprImpl(Op, Ty, Cache);
1521 auto InsertResult = Cache.insert({{Op, Ty}, ZExt});
1522 assert(InsertResult.second && "Expect the key was not in the cache");
1527 /// The real implementation of getZeroExtendExpr.
1528 const SCEV *ScalarEvolution::getZeroExtendExprImpl(const SCEV *Op, Type *Ty,
1529 ExtendCacheTy &Cache) {
1530 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1531 "This is not an extending conversion!");
1532 assert(isSCEVable(Ty) &&
1533 "This is not a conversion to a SCEVable type!");
1534 Ty = getEffectiveSCEVType(Ty);
1536 // Fold if the operand is constant.
1537 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1539 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty)));
1541 // zext(zext(x)) --> zext(x)
1542 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1543 return getZeroExtendExprCached(SZ->getOperand(), Ty, Cache);
1545 // Before doing any expensive analysis, check to see if we've already
1546 // computed a SCEV for this Op and Ty.
1547 FoldingSetNodeID ID;
1548 ID.AddInteger(scZeroExtend);
1552 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1554 // zext(trunc(x)) --> zext(x) or x or trunc(x)
1555 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1556 // It's possible the bits taken off by the truncate were all zero bits. If
1557 // so, we should be able to simplify this further.
1558 const SCEV *X = ST->getOperand();
1559 ConstantRange CR = getUnsignedRange(X);
1560 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1561 unsigned NewBits = getTypeSizeInBits(Ty);
1562 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
1563 CR.zextOrTrunc(NewBits)))
1564 return getTruncateOrZeroExtend(X, Ty);
1567 // If the input value is a chrec scev, and we can prove that the value
1568 // did not overflow the old, smaller, value, we can zero extend all of the
1569 // operands (often constants). This allows analysis of something like
1570 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
1571 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1572 if (AR->isAffine()) {
1573 const SCEV *Start = AR->getStart();
1574 const SCEV *Step = AR->getStepRecurrence(*this);
1575 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1576 const Loop *L = AR->getLoop();
1578 if (!AR->hasNoUnsignedWrap()) {
1579 auto NewFlags = proveNoWrapViaConstantRanges(AR);
1580 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(NewFlags);
1583 // If we have special knowledge that this addrec won't overflow,
1584 // we don't need to do any further analysis.
1585 if (AR->hasNoUnsignedWrap())
1586 return getAddRecExpr(
1587 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Cache),
1588 getZeroExtendExprCached(Step, Ty, Cache), L, AR->getNoWrapFlags());
1590 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1591 // Note that this serves two purposes: It filters out loops that are
1592 // simply not analyzable, and it covers the case where this code is
1593 // being called from within backedge-taken count analysis, such that
1594 // attempting to ask for the backedge-taken count would likely result
1595 // in infinite recursion. In the later case, the analysis code will
1596 // cope with a conservative value, and it will take care to purge
1597 // that value once it has finished.
1598 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1599 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1600 // Manually compute the final value for AR, checking for
1603 // Check whether the backedge-taken count can be losslessly casted to
1604 // the addrec's type. The count is always unsigned.
1605 const SCEV *CastedMaxBECount =
1606 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1607 const SCEV *RecastedMaxBECount =
1608 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1609 if (MaxBECount == RecastedMaxBECount) {
1610 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1611 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1612 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1614 getZeroExtendExprCached(getAddExpr(Start, ZMul), WideTy, Cache);
1615 const SCEV *WideStart = getZeroExtendExprCached(Start, WideTy, Cache);
1616 const SCEV *WideMaxBECount =
1617 getZeroExtendExprCached(CastedMaxBECount, WideTy, Cache);
1618 const SCEV *OperandExtendedAdd = getAddExpr(
1619 WideStart, getMulExpr(WideMaxBECount, getZeroExtendExprCached(
1620 Step, WideTy, Cache)));
1621 if (ZAdd == OperandExtendedAdd) {
1622 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1623 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1624 // Return the expression with the addrec on the outside.
1625 return getAddRecExpr(
1626 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Cache),
1627 getZeroExtendExprCached(Step, Ty, Cache), L,
1628 AR->getNoWrapFlags());
1630 // Similar to above, only this time treat the step value as signed.
1631 // This covers loops that count down.
1632 OperandExtendedAdd =
1633 getAddExpr(WideStart,
1634 getMulExpr(WideMaxBECount,
1635 getSignExtendExpr(Step, WideTy)));
1636 if (ZAdd == OperandExtendedAdd) {
1637 // Cache knowledge of AR NW, which is propagated to this AddRec.
1638 // Negative step causes unsigned wrap, but it still can't self-wrap.
1639 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1640 // Return the expression with the addrec on the outside.
1641 return getAddRecExpr(
1642 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Cache),
1643 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1648 // Normally, in the cases we can prove no-overflow via a
1649 // backedge guarding condition, we can also compute a backedge
1650 // taken count for the loop. The exceptions are assumptions and
1651 // guards present in the loop -- SCEV is not great at exploiting
1652 // these to compute max backedge taken counts, but can still use
1653 // these to prove lack of overflow. Use this fact to avoid
1654 // doing extra work that may not pay off.
1655 if (!isa<SCEVCouldNotCompute>(MaxBECount) || HasGuards ||
1656 !AC.assumptions().empty()) {
1657 // If the backedge is guarded by a comparison with the pre-inc
1658 // value the addrec is safe. Also, if the entry is guarded by
1659 // a comparison with the start value and the backedge is
1660 // guarded by a comparison with the post-inc value, the addrec
1662 if (isKnownPositive(Step)) {
1663 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1664 getUnsignedRange(Step).getUnsignedMax());
1665 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1666 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1667 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1668 AR->getPostIncExpr(*this), N))) {
1669 // Cache knowledge of AR NUW, which is propagated to this
1671 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1672 // Return the expression with the addrec on the outside.
1673 return getAddRecExpr(
1674 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Cache),
1675 getZeroExtendExprCached(Step, Ty, Cache), L,
1676 AR->getNoWrapFlags());
1678 } else if (isKnownNegative(Step)) {
1679 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1680 getSignedRange(Step).getSignedMin());
1681 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1682 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1683 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1684 AR->getPostIncExpr(*this), N))) {
1685 // Cache knowledge of AR NW, which is propagated to this
1686 // AddRec. Negative step causes unsigned wrap, but it
1687 // still can't self-wrap.
1688 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1689 // Return the expression with the addrec on the outside.
1690 return getAddRecExpr(
1691 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Cache),
1692 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1697 if (proveNoWrapByVaryingStart<SCEVZeroExtendExpr>(Start, Step, L)) {
1698 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1699 return getAddRecExpr(
1700 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Cache),
1701 getZeroExtendExprCached(Step, Ty, Cache), L, AR->getNoWrapFlags());
1705 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1706 // zext((A + B + ...)<nuw>) --> (zext(A) + zext(B) + ...)<nuw>
1707 if (SA->hasNoUnsignedWrap()) {
1708 // If the addition does not unsign overflow then we can, by definition,
1709 // commute the zero extension with the addition operation.
1710 SmallVector<const SCEV *, 4> Ops;
1711 for (const auto *Op : SA->operands())
1712 Ops.push_back(getZeroExtendExprCached(Op, Ty, Cache));
1713 return getAddExpr(Ops, SCEV::FlagNUW);
1717 // The cast wasn't folded; create an explicit cast node.
1718 // Recompute the insert position, as it may have been invalidated.
1719 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1720 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1722 UniqueSCEVs.InsertNode(S, IP);
1726 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op, Type *Ty) {
1727 // Use the local cache to prevent exponential behavior of
1728 // getSignExtendExprImpl.
1729 ExtendCacheTy Cache;
1730 return getSignExtendExprCached(Op, Ty, Cache);
1733 /// Query \p Cache before calling getSignExtendExprImpl. If there is no
1734 /// related entry in the \p Cache, call getSignExtendExprImpl and save
1735 /// the result in the \p Cache.
1736 const SCEV *ScalarEvolution::getSignExtendExprCached(const SCEV *Op, Type *Ty,
1737 ExtendCacheTy &Cache) {
1738 auto It = Cache.find({Op, Ty});
1739 if (It != Cache.end())
1741 const SCEV *SExt = getSignExtendExprImpl(Op, Ty, Cache);
1742 auto InsertResult = Cache.insert({{Op, Ty}, SExt});
1743 assert(InsertResult.second && "Expect the key was not in the cache");
1748 /// The real implementation of getSignExtendExpr.
1749 const SCEV *ScalarEvolution::getSignExtendExprImpl(const SCEV *Op, Type *Ty,
1750 ExtendCacheTy &Cache) {
1751 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1752 "This is not an extending conversion!");
1753 assert(isSCEVable(Ty) &&
1754 "This is not a conversion to a SCEVable type!");
1755 Ty = getEffectiveSCEVType(Ty);
1757 // Fold if the operand is constant.
1758 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1760 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty)));
1762 // sext(sext(x)) --> sext(x)
1763 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1764 return getSignExtendExprCached(SS->getOperand(), Ty, Cache);
1766 // sext(zext(x)) --> zext(x)
1767 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1768 return getZeroExtendExpr(SZ->getOperand(), Ty);
1770 // Before doing any expensive analysis, check to see if we've already
1771 // computed a SCEV for this Op and Ty.
1772 FoldingSetNodeID ID;
1773 ID.AddInteger(scSignExtend);
1777 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1779 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1780 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1781 // It's possible the bits taken off by the truncate were all sign bits. If
1782 // so, we should be able to simplify this further.
1783 const SCEV *X = ST->getOperand();
1784 ConstantRange CR = getSignedRange(X);
1785 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1786 unsigned NewBits = getTypeSizeInBits(Ty);
1787 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1788 CR.sextOrTrunc(NewBits)))
1789 return getTruncateOrSignExtend(X, Ty);
1792 // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
1793 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1794 if (SA->getNumOperands() == 2) {
1795 auto *SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
1796 auto *SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
1798 if (auto *SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
1799 const APInt &C1 = SC1->getAPInt();
1800 const APInt &C2 = SC2->getAPInt();
1801 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
1802 C2.ugt(C1) && C2.isPowerOf2())
1803 return getAddExpr(getSignExtendExprCached(SC1, Ty, Cache),
1804 getSignExtendExprCached(SMul, Ty, Cache));
1809 // sext((A + B + ...)<nsw>) --> (sext(A) + sext(B) + ...)<nsw>
1810 if (SA->hasNoSignedWrap()) {
1811 // If the addition does not sign overflow then we can, by definition,
1812 // commute the sign extension with the addition operation.
1813 SmallVector<const SCEV *, 4> Ops;
1814 for (const auto *Op : SA->operands())
1815 Ops.push_back(getSignExtendExprCached(Op, Ty, Cache));
1816 return getAddExpr(Ops, SCEV::FlagNSW);
1819 // If the input value is a chrec scev, and we can prove that the value
1820 // did not overflow the old, smaller, value, we can sign extend all of the
1821 // operands (often constants). This allows analysis of something like
1822 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1823 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1824 if (AR->isAffine()) {
1825 const SCEV *Start = AR->getStart();
1826 const SCEV *Step = AR->getStepRecurrence(*this);
1827 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1828 const Loop *L = AR->getLoop();
1830 if (!AR->hasNoSignedWrap()) {
1831 auto NewFlags = proveNoWrapViaConstantRanges(AR);
1832 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(NewFlags);
1835 // If we have special knowledge that this addrec won't overflow,
1836 // we don't need to do any further analysis.
1837 if (AR->hasNoSignedWrap())
1838 return getAddRecExpr(
1839 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Cache),
1840 getSignExtendExprCached(Step, Ty, Cache), L, SCEV::FlagNSW);
1842 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1843 // Note that this serves two purposes: It filters out loops that are
1844 // simply not analyzable, and it covers the case where this code is
1845 // being called from within backedge-taken count analysis, such that
1846 // attempting to ask for the backedge-taken count would likely result
1847 // in infinite recursion. In the later case, the analysis code will
1848 // cope with a conservative value, and it will take care to purge
1849 // that value once it has finished.
1850 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1851 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1852 // Manually compute the final value for AR, checking for
1855 // Check whether the backedge-taken count can be losslessly casted to
1856 // the addrec's type. The count is always unsigned.
1857 const SCEV *CastedMaxBECount =
1858 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1859 const SCEV *RecastedMaxBECount =
1860 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1861 if (MaxBECount == RecastedMaxBECount) {
1862 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1863 // Check whether Start+Step*MaxBECount has no signed overflow.
1864 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1866 getSignExtendExprCached(getAddExpr(Start, SMul), WideTy, Cache);
1867 const SCEV *WideStart = getSignExtendExprCached(Start, WideTy, Cache);
1868 const SCEV *WideMaxBECount =
1869 getZeroExtendExpr(CastedMaxBECount, WideTy);
1870 const SCEV *OperandExtendedAdd = getAddExpr(
1871 WideStart, getMulExpr(WideMaxBECount, getSignExtendExprCached(
1872 Step, WideTy, Cache)));
1873 if (SAdd == OperandExtendedAdd) {
1874 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1875 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1876 // Return the expression with the addrec on the outside.
1877 return getAddRecExpr(
1878 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Cache),
1879 getSignExtendExprCached(Step, Ty, Cache), L,
1880 AR->getNoWrapFlags());
1882 // Similar to above, only this time treat the step value as unsigned.
1883 // This covers loops that count up with an unsigned step.
1884 OperandExtendedAdd =
1885 getAddExpr(WideStart,
1886 getMulExpr(WideMaxBECount,
1887 getZeroExtendExpr(Step, WideTy)));
1888 if (SAdd == OperandExtendedAdd) {
1889 // If AR wraps around then
1891 // abs(Step) * MaxBECount > unsigned-max(AR->getType())
1892 // => SAdd != OperandExtendedAdd
1894 // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=>
1895 // (SAdd == OperandExtendedAdd => AR is NW)
1897 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1899 // Return the expression with the addrec on the outside.
1900 return getAddRecExpr(
1901 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Cache),
1902 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1907 // Normally, in the cases we can prove no-overflow via a
1908 // backedge guarding condition, we can also compute a backedge
1909 // taken count for the loop. The exceptions are assumptions and
1910 // guards present in the loop -- SCEV is not great at exploiting
1911 // these to compute max backedge taken counts, but can still use
1912 // these to prove lack of overflow. Use this fact to avoid
1913 // doing extra work that may not pay off.
1915 if (!isa<SCEVCouldNotCompute>(MaxBECount) || HasGuards ||
1916 !AC.assumptions().empty()) {
1917 // If the backedge is guarded by a comparison with the pre-inc
1918 // value the addrec is safe. Also, if the entry is guarded by
1919 // a comparison with the start value and the backedge is
1920 // guarded by a comparison with the post-inc value, the addrec
1922 ICmpInst::Predicate Pred;
1923 const SCEV *OverflowLimit =
1924 getSignedOverflowLimitForStep(Step, &Pred, this);
1925 if (OverflowLimit &&
1926 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1927 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1928 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1930 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1931 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1932 return getAddRecExpr(
1933 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Cache),
1934 getSignExtendExprCached(Step, Ty, Cache), L,
1935 AR->getNoWrapFlags());
1939 // If Start and Step are constants, check if we can apply this
1941 // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
1942 auto *SC1 = dyn_cast<SCEVConstant>(Start);
1943 auto *SC2 = dyn_cast<SCEVConstant>(Step);
1945 const APInt &C1 = SC1->getAPInt();
1946 const APInt &C2 = SC2->getAPInt();
1947 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
1949 Start = getSignExtendExprCached(Start, Ty, Cache);
1950 const SCEV *NewAR = getAddRecExpr(getZero(AR->getType()), Step, L,
1951 AR->getNoWrapFlags());
1952 return getAddExpr(Start, getSignExtendExprCached(NewAR, Ty, Cache));
1956 if (proveNoWrapByVaryingStart<SCEVSignExtendExpr>(Start, Step, L)) {
1957 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1958 return getAddRecExpr(
1959 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Cache),
1960 getSignExtendExprCached(Step, Ty, Cache), L, AR->getNoWrapFlags());
1964 // If the input value is provably positive and we could not simplify
1965 // away the sext build a zext instead.
1966 if (isKnownNonNegative(Op))
1967 return getZeroExtendExpr(Op, Ty);
1969 // The cast wasn't folded; create an explicit cast node.
1970 // Recompute the insert position, as it may have been invalidated.
1971 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1972 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1974 UniqueSCEVs.InsertNode(S, IP);
1978 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1979 /// unspecified bits out to the given type.
1981 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1983 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1984 "This is not an extending conversion!");
1985 assert(isSCEVable(Ty) &&
1986 "This is not a conversion to a SCEVable type!");
1987 Ty = getEffectiveSCEVType(Ty);
1989 // Sign-extend negative constants.
1990 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1991 if (SC->getAPInt().isNegative())
1992 return getSignExtendExpr(Op, Ty);
1994 // Peel off a truncate cast.
1995 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1996 const SCEV *NewOp = T->getOperand();
1997 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1998 return getAnyExtendExpr(NewOp, Ty);
1999 return getTruncateOrNoop(NewOp, Ty);
2002 // Next try a zext cast. If the cast is folded, use it.
2003 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
2004 if (!isa<SCEVZeroExtendExpr>(ZExt))
2007 // Next try a sext cast. If the cast is folded, use it.
2008 const SCEV *SExt = getSignExtendExpr(Op, Ty);
2009 if (!isa<SCEVSignExtendExpr>(SExt))
2012 // Force the cast to be folded into the operands of an addrec.
2013 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
2014 SmallVector<const SCEV *, 4> Ops;
2015 for (const SCEV *Op : AR->operands())
2016 Ops.push_back(getAnyExtendExpr(Op, Ty));
2017 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
2020 // If the expression is obviously signed, use the sext cast value.
2021 if (isa<SCEVSMaxExpr>(Op))
2024 // Absent any other information, use the zext cast value.
2028 /// Process the given Ops list, which is a list of operands to be added under
2029 /// the given scale, update the given map. This is a helper function for
2030 /// getAddRecExpr. As an example of what it does, given a sequence of operands
2031 /// that would form an add expression like this:
2033 /// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
2035 /// where A and B are constants, update the map with these values:
2037 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
2039 /// and add 13 + A*B*29 to AccumulatedConstant.
2040 /// This will allow getAddRecExpr to produce this:
2042 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
2044 /// This form often exposes folding opportunities that are hidden in
2045 /// the original operand list.
2047 /// Return true iff it appears that any interesting folding opportunities
2048 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
2049 /// the common case where no interesting opportunities are present, and
2050 /// is also used as a check to avoid infinite recursion.
2053 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
2054 SmallVectorImpl<const SCEV *> &NewOps,
2055 APInt &AccumulatedConstant,
2056 const SCEV *const *Ops, size_t NumOperands,
2058 ScalarEvolution &SE) {
2059 bool Interesting = false;
2061 // Iterate over the add operands. They are sorted, with constants first.
2063 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
2065 // Pull a buried constant out to the outside.
2066 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
2068 AccumulatedConstant += Scale * C->getAPInt();
2071 // Next comes everything else. We're especially interested in multiplies
2072 // here, but they're in the middle, so just visit the rest with one loop.
2073 for (; i != NumOperands; ++i) {
2074 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
2075 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
2077 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getAPInt();
2078 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
2079 // A multiplication of a constant with another add; recurse.
2080 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
2082 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
2083 Add->op_begin(), Add->getNumOperands(),
2086 // A multiplication of a constant with some other value. Update
2088 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
2089 const SCEV *Key = SE.getMulExpr(MulOps);
2090 auto Pair = M.insert({Key, NewScale});
2092 NewOps.push_back(Pair.first->first);
2094 Pair.first->second += NewScale;
2095 // The map already had an entry for this value, which may indicate
2096 // a folding opportunity.
2101 // An ordinary operand. Update the map.
2102 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
2103 M.insert({Ops[i], Scale});
2105 NewOps.push_back(Pair.first->first);
2107 Pair.first->second += Scale;
2108 // The map already had an entry for this value, which may indicate
2109 // a folding opportunity.
2118 // We're trying to construct a SCEV of type `Type' with `Ops' as operands and
2119 // `OldFlags' as can't-wrap behavior. Infer a more aggressive set of
2120 // can't-overflow flags for the operation if possible.
2121 static SCEV::NoWrapFlags
2122 StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
2123 const SmallVectorImpl<const SCEV *> &Ops,
2124 SCEV::NoWrapFlags Flags) {
2125 using namespace std::placeholders;
2126 typedef OverflowingBinaryOperator OBO;
2129 Type == scAddExpr || Type == scAddRecExpr || Type == scMulExpr;
2131 assert(CanAnalyze && "don't call from other places!");
2133 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2134 SCEV::NoWrapFlags SignOrUnsignWrap =
2135 ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
2137 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2138 auto IsKnownNonNegative = [&](const SCEV *S) {
2139 return SE->isKnownNonNegative(S);
2142 if (SignOrUnsignWrap == SCEV::FlagNSW && all_of(Ops, IsKnownNonNegative))
2144 ScalarEvolution::setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2146 SignOrUnsignWrap = ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
2148 if (SignOrUnsignWrap != SignOrUnsignMask && Type == scAddExpr &&
2149 Ops.size() == 2 && isa<SCEVConstant>(Ops[0])) {
2151 // (A + C) --> (A + C)<nsw> if the addition does not sign overflow
2152 // (A + C) --> (A + C)<nuw> if the addition does not unsign overflow
2154 const APInt &C = cast<SCEVConstant>(Ops[0])->getAPInt();
2155 if (!(SignOrUnsignWrap & SCEV::FlagNSW)) {
2156 auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
2157 Instruction::Add, C, OBO::NoSignedWrap);
2158 if (NSWRegion.contains(SE->getSignedRange(Ops[1])))
2159 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
2161 if (!(SignOrUnsignWrap & SCEV::FlagNUW)) {
2162 auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
2163 Instruction::Add, C, OBO::NoUnsignedWrap);
2164 if (NUWRegion.contains(SE->getUnsignedRange(Ops[1])))
2165 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
2172 /// Get a canonical add expression, or something simpler if possible.
2173 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
2174 SCEV::NoWrapFlags Flags,
2176 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
2177 "only nuw or nsw allowed");
2178 assert(!Ops.empty() && "Cannot get empty add!");
2179 if (Ops.size() == 1) return Ops[0];
2181 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2182 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2183 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2184 "SCEVAddExpr operand types don't match!");
2187 // Sort by complexity, this groups all similar expression types together.
2188 GroupByComplexity(Ops, &LI);
2190 Flags = StrengthenNoWrapFlags(this, scAddExpr, Ops, Flags);
2192 // If there are any constants, fold them together.
2194 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2196 assert(Idx < Ops.size());
2197 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2198 // We found two constants, fold them together!
2199 Ops[0] = getConstant(LHSC->getAPInt() + RHSC->getAPInt());
2200 if (Ops.size() == 2) return Ops[0];
2201 Ops.erase(Ops.begin()+1); // Erase the folded element
2202 LHSC = cast<SCEVConstant>(Ops[0]);
2205 // If we are left with a constant zero being added, strip it off.
2206 if (LHSC->getValue()->isZero()) {
2207 Ops.erase(Ops.begin());
2211 if (Ops.size() == 1) return Ops[0];
2214 // Limit recursion calls depth
2215 if (Depth > MaxAddExprDepth)
2216 return getOrCreateAddExpr(Ops, Flags);
2218 // Okay, check to see if the same value occurs in the operand list more than
2219 // once. If so, merge them together into an multiply expression. Since we
2220 // sorted the list, these values are required to be adjacent.
2221 Type *Ty = Ops[0]->getType();
2222 bool FoundMatch = false;
2223 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
2224 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
2225 // Scan ahead to count how many equal operands there are.
2227 while (i+Count != e && Ops[i+Count] == Ops[i])
2229 // Merge the values into a multiply.
2230 const SCEV *Scale = getConstant(Ty, Count);
2231 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
2232 if (Ops.size() == Count)
2235 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
2236 --i; e -= Count - 1;
2240 return getAddExpr(Ops, Flags);
2242 // Check for truncates. If all the operands are truncated from the same
2243 // type, see if factoring out the truncate would permit the result to be
2244 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
2245 // if the contents of the resulting outer trunc fold to something simple.
2246 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
2247 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
2248 Type *DstType = Trunc->getType();
2249 Type *SrcType = Trunc->getOperand()->getType();
2250 SmallVector<const SCEV *, 8> LargeOps;
2252 // Check all the operands to see if they can be represented in the
2253 // source type of the truncate.
2254 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
2255 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
2256 if (T->getOperand()->getType() != SrcType) {
2260 LargeOps.push_back(T->getOperand());
2261 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
2262 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
2263 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
2264 SmallVector<const SCEV *, 8> LargeMulOps;
2265 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
2266 if (const SCEVTruncateExpr *T =
2267 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
2268 if (T->getOperand()->getType() != SrcType) {
2272 LargeMulOps.push_back(T->getOperand());
2273 } else if (const auto *C = dyn_cast<SCEVConstant>(M->getOperand(j))) {
2274 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
2281 LargeOps.push_back(getMulExpr(LargeMulOps));
2288 // Evaluate the expression in the larger type.
2289 const SCEV *Fold = getAddExpr(LargeOps, Flags, Depth + 1);
2290 // If it folds to something simple, use it. Otherwise, don't.
2291 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
2292 return getTruncateExpr(Fold, DstType);
2296 // Skip past any other cast SCEVs.
2297 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
2300 // If there are add operands they would be next.
2301 if (Idx < Ops.size()) {
2302 bool DeletedAdd = false;
2303 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
2304 if (Ops.size() > AddOpsInlineThreshold ||
2305 Add->getNumOperands() > AddOpsInlineThreshold)
2307 // If we have an add, expand the add operands onto the end of the operands
2309 Ops.erase(Ops.begin()+Idx);
2310 Ops.append(Add->op_begin(), Add->op_end());
2314 // If we deleted at least one add, we added operands to the end of the list,
2315 // and they are not necessarily sorted. Recurse to resort and resimplify
2316 // any operands we just acquired.
2318 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2321 // Skip over the add expression until we get to a multiply.
2322 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2325 // Check to see if there are any folding opportunities present with
2326 // operands multiplied by constant values.
2327 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
2328 uint64_t BitWidth = getTypeSizeInBits(Ty);
2329 DenseMap<const SCEV *, APInt> M;
2330 SmallVector<const SCEV *, 8> NewOps;
2331 APInt AccumulatedConstant(BitWidth, 0);
2332 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
2333 Ops.data(), Ops.size(),
2334 APInt(BitWidth, 1), *this)) {
2335 struct APIntCompare {
2336 bool operator()(const APInt &LHS, const APInt &RHS) const {
2337 return LHS.ult(RHS);
2341 // Some interesting folding opportunity is present, so its worthwhile to
2342 // re-generate the operands list. Group the operands by constant scale,
2343 // to avoid multiplying by the same constant scale multiple times.
2344 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
2345 for (const SCEV *NewOp : NewOps)
2346 MulOpLists[M.find(NewOp)->second].push_back(NewOp);
2347 // Re-generate the operands list.
2349 if (AccumulatedConstant != 0)
2350 Ops.push_back(getConstant(AccumulatedConstant));
2351 for (auto &MulOp : MulOpLists)
2352 if (MulOp.first != 0)
2353 Ops.push_back(getMulExpr(
2354 getConstant(MulOp.first),
2355 getAddExpr(MulOp.second, SCEV::FlagAnyWrap, Depth + 1)));
2358 if (Ops.size() == 1)
2360 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2364 // If we are adding something to a multiply expression, make sure the
2365 // something is not already an operand of the multiply. If so, merge it into
2367 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
2368 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
2369 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
2370 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
2371 if (isa<SCEVConstant>(MulOpSCEV))
2373 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
2374 if (MulOpSCEV == Ops[AddOp]) {
2375 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
2376 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
2377 if (Mul->getNumOperands() != 2) {
2378 // If the multiply has more than two operands, we must get the
2380 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2381 Mul->op_begin()+MulOp);
2382 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2383 InnerMul = getMulExpr(MulOps);
2385 SmallVector<const SCEV *, 2> TwoOps = {getOne(Ty), InnerMul};
2386 const SCEV *AddOne = getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1);
2387 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
2388 if (Ops.size() == 2) return OuterMul;
2390 Ops.erase(Ops.begin()+AddOp);
2391 Ops.erase(Ops.begin()+Idx-1);
2393 Ops.erase(Ops.begin()+Idx);
2394 Ops.erase(Ops.begin()+AddOp-1);
2396 Ops.push_back(OuterMul);
2397 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2400 // Check this multiply against other multiplies being added together.
2401 for (unsigned OtherMulIdx = Idx+1;
2402 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
2404 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
2405 // If MulOp occurs in OtherMul, we can fold the two multiplies
2407 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
2408 OMulOp != e; ++OMulOp)
2409 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
2410 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
2411 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
2412 if (Mul->getNumOperands() != 2) {
2413 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2414 Mul->op_begin()+MulOp);
2415 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2416 InnerMul1 = getMulExpr(MulOps);
2418 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
2419 if (OtherMul->getNumOperands() != 2) {
2420 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
2421 OtherMul->op_begin()+OMulOp);
2422 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
2423 InnerMul2 = getMulExpr(MulOps);
2425 SmallVector<const SCEV *, 2> TwoOps = {InnerMul1, InnerMul2};
2426 const SCEV *InnerMulSum =
2427 getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1);
2428 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
2429 if (Ops.size() == 2) return OuterMul;
2430 Ops.erase(Ops.begin()+Idx);
2431 Ops.erase(Ops.begin()+OtherMulIdx-1);
2432 Ops.push_back(OuterMul);
2433 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2439 // If there are any add recurrences in the operands list, see if any other
2440 // added values are loop invariant. If so, we can fold them into the
2442 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2445 // Scan over all recurrences, trying to fold loop invariants into them.
2446 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2447 // Scan all of the other operands to this add and add them to the vector if
2448 // they are loop invariant w.r.t. the recurrence.
2449 SmallVector<const SCEV *, 8> LIOps;
2450 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2451 const Loop *AddRecLoop = AddRec->getLoop();
2452 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2453 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2454 LIOps.push_back(Ops[i]);
2455 Ops.erase(Ops.begin()+i);
2459 // If we found some loop invariants, fold them into the recurrence.
2460 if (!LIOps.empty()) {
2461 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
2462 LIOps.push_back(AddRec->getStart());
2464 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2466 // This follows from the fact that the no-wrap flags on the outer add
2467 // expression are applicable on the 0th iteration, when the add recurrence
2468 // will be equal to its start value.
2469 AddRecOps[0] = getAddExpr(LIOps, Flags, Depth + 1);
2471 // Build the new addrec. Propagate the NUW and NSW flags if both the
2472 // outer add and the inner addrec are guaranteed to have no overflow.
2473 // Always propagate NW.
2474 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
2475 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
2477 // If all of the other operands were loop invariant, we are done.
2478 if (Ops.size() == 1) return NewRec;
2480 // Otherwise, add the folded AddRec by the non-invariant parts.
2481 for (unsigned i = 0;; ++i)
2482 if (Ops[i] == AddRec) {
2486 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2489 // Okay, if there weren't any loop invariants to be folded, check to see if
2490 // there are multiple AddRec's with the same loop induction variable being
2491 // added together. If so, we can fold them.
2492 for (unsigned OtherIdx = Idx+1;
2493 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2495 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2496 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
2497 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2499 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2501 if (const auto *OtherAddRec = dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2502 if (OtherAddRec->getLoop() == AddRecLoop) {
2503 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
2505 if (i >= AddRecOps.size()) {
2506 AddRecOps.append(OtherAddRec->op_begin()+i,
2507 OtherAddRec->op_end());
2510 SmallVector<const SCEV *, 2> TwoOps = {
2511 AddRecOps[i], OtherAddRec->getOperand(i)};
2512 AddRecOps[i] = getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1);
2514 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2516 // Step size has changed, so we cannot guarantee no self-wraparound.
2517 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
2518 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2521 // Otherwise couldn't fold anything into this recurrence. Move onto the
2525 // Okay, it looks like we really DO need an add expr. Check to see if we
2526 // already have one, otherwise create a new one.
2527 return getOrCreateAddExpr(Ops, Flags);
2531 ScalarEvolution::getOrCreateAddExpr(SmallVectorImpl<const SCEV *> &Ops,
2532 SCEV::NoWrapFlags Flags) {
2533 FoldingSetNodeID ID;
2534 ID.AddInteger(scAddExpr);
2535 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2536 ID.AddPointer(Ops[i]);
2539 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2541 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2542 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2543 S = new (SCEVAllocator)
2544 SCEVAddExpr(ID.Intern(SCEVAllocator), O, Ops.size());
2545 UniqueSCEVs.InsertNode(S, IP);
2547 S->setNoWrapFlags(Flags);
2551 static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
2553 if (j > 1 && k / j != i) Overflow = true;
2557 /// Compute the result of "n choose k", the binomial coefficient. If an
2558 /// intermediate computation overflows, Overflow will be set and the return will
2559 /// be garbage. Overflow is not cleared on absence of overflow.
2560 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
2561 // We use the multiplicative formula:
2562 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
2563 // At each iteration, we take the n-th term of the numeral and divide by the
2564 // (k-n)th term of the denominator. This division will always produce an
2565 // integral result, and helps reduce the chance of overflow in the
2566 // intermediate computations. However, we can still overflow even when the
2567 // final result would fit.
2569 if (n == 0 || n == k) return 1;
2570 if (k > n) return 0;
2576 for (uint64_t i = 1; i <= k; ++i) {
2577 r = umul_ov(r, n-(i-1), Overflow);
2583 /// Determine if any of the operands in this SCEV are a constant or if
2584 /// any of the add or multiply expressions in this SCEV contain a constant.
2585 static bool containsConstantSomewhere(const SCEV *StartExpr) {
2586 SmallVector<const SCEV *, 4> Ops;
2587 Ops.push_back(StartExpr);
2588 while (!Ops.empty()) {
2589 const SCEV *CurrentExpr = Ops.pop_back_val();
2590 if (isa<SCEVConstant>(*CurrentExpr))
2593 if (isa<SCEVAddExpr>(*CurrentExpr) || isa<SCEVMulExpr>(*CurrentExpr)) {
2594 const auto *CurrentNAry = cast<SCEVNAryExpr>(CurrentExpr);
2595 Ops.append(CurrentNAry->op_begin(), CurrentNAry->op_end());
2601 /// Get a canonical multiply expression, or something simpler if possible.
2602 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
2603 SCEV::NoWrapFlags Flags) {
2604 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
2605 "only nuw or nsw allowed");
2606 assert(!Ops.empty() && "Cannot get empty mul!");
2607 if (Ops.size() == 1) return Ops[0];
2609 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2610 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2611 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2612 "SCEVMulExpr operand types don't match!");
2615 // Sort by complexity, this groups all similar expression types together.
2616 GroupByComplexity(Ops, &LI);
2618 Flags = StrengthenNoWrapFlags(this, scMulExpr, Ops, Flags);
2620 // If there are any constants, fold them together.
2622 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2624 // C1*(C2+V) -> C1*C2 + C1*V
2625 if (Ops.size() == 2)
2626 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
2627 // If any of Add's ops are Adds or Muls with a constant,
2628 // apply this transformation as well.
2629 if (Add->getNumOperands() == 2)
2630 if (containsConstantSomewhere(Add))
2631 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
2632 getMulExpr(LHSC, Add->getOperand(1)));
2635 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2636 // We found two constants, fold them together!
2638 ConstantInt::get(getContext(), LHSC->getAPInt() * RHSC->getAPInt());
2639 Ops[0] = getConstant(Fold);
2640 Ops.erase(Ops.begin()+1); // Erase the folded element
2641 if (Ops.size() == 1) return Ops[0];
2642 LHSC = cast<SCEVConstant>(Ops[0]);
2645 // If we are left with a constant one being multiplied, strip it off.
2646 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
2647 Ops.erase(Ops.begin());
2649 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
2650 // If we have a multiply of zero, it will always be zero.
2652 } else if (Ops[0]->isAllOnesValue()) {
2653 // If we have a mul by -1 of an add, try distributing the -1 among the
2655 if (Ops.size() == 2) {
2656 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
2657 SmallVector<const SCEV *, 4> NewOps;
2658 bool AnyFolded = false;
2659 for (const SCEV *AddOp : Add->operands()) {
2660 const SCEV *Mul = getMulExpr(Ops[0], AddOp);
2661 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
2662 NewOps.push_back(Mul);
2665 return getAddExpr(NewOps);
2666 } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
2667 // Negation preserves a recurrence's no self-wrap property.
2668 SmallVector<const SCEV *, 4> Operands;
2669 for (const SCEV *AddRecOp : AddRec->operands())
2670 Operands.push_back(getMulExpr(Ops[0], AddRecOp));
2672 return getAddRecExpr(Operands, AddRec->getLoop(),
2673 AddRec->getNoWrapFlags(SCEV::FlagNW));
2678 if (Ops.size() == 1)
2682 // Skip over the add expression until we get to a multiply.
2683 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2686 // If there are mul operands inline them all into this expression.
2687 if (Idx < Ops.size()) {
2688 bool DeletedMul = false;
2689 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
2690 if (Ops.size() > MulOpsInlineThreshold)
2692 // If we have an mul, expand the mul operands onto the end of the operands
2694 Ops.erase(Ops.begin()+Idx);
2695 Ops.append(Mul->op_begin(), Mul->op_end());
2699 // If we deleted at least one mul, we added operands to the end of the list,
2700 // and they are not necessarily sorted. Recurse to resort and resimplify
2701 // any operands we just acquired.
2703 return getMulExpr(Ops);
2706 // If there are any add recurrences in the operands list, see if any other
2707 // added values are loop invariant. If so, we can fold them into the
2709 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2712 // Scan over all recurrences, trying to fold loop invariants into them.
2713 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2714 // Scan all of the other operands to this mul and add them to the vector if
2715 // they are loop invariant w.r.t. the recurrence.
2716 SmallVector<const SCEV *, 8> LIOps;
2717 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2718 const Loop *AddRecLoop = AddRec->getLoop();
2719 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2720 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2721 LIOps.push_back(Ops[i]);
2722 Ops.erase(Ops.begin()+i);
2726 // If we found some loop invariants, fold them into the recurrence.
2727 if (!LIOps.empty()) {
2728 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
2729 SmallVector<const SCEV *, 4> NewOps;
2730 NewOps.reserve(AddRec->getNumOperands());
2731 const SCEV *Scale = getMulExpr(LIOps);
2732 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2733 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2735 // Build the new addrec. Propagate the NUW and NSW flags if both the
2736 // outer mul and the inner addrec are guaranteed to have no overflow.
2738 // No self-wrap cannot be guaranteed after changing the step size, but
2739 // will be inferred if either NUW or NSW is true.
2740 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2741 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2743 // If all of the other operands were loop invariant, we are done.
2744 if (Ops.size() == 1) return NewRec;
2746 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2747 for (unsigned i = 0;; ++i)
2748 if (Ops[i] == AddRec) {
2752 return getMulExpr(Ops);
2755 // Okay, if there weren't any loop invariants to be folded, check to see if
2756 // there are multiple AddRec's with the same loop induction variable being
2757 // multiplied together. If so, we can fold them.
2759 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2760 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2761 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2762 // ]]],+,...up to x=2n}.
2763 // Note that the arguments to choose() are always integers with values
2764 // known at compile time, never SCEV objects.
2766 // The implementation avoids pointless extra computations when the two
2767 // addrec's are of different length (mathematically, it's equivalent to
2768 // an infinite stream of zeros on the right).
2769 bool OpsModified = false;
2770 for (unsigned OtherIdx = Idx+1;
2771 OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2773 const SCEVAddRecExpr *OtherAddRec =
2774 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
2775 if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
2778 bool Overflow = false;
2779 Type *Ty = AddRec->getType();
2780 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2781 SmallVector<const SCEV*, 7> AddRecOps;
2782 for (int x = 0, xe = AddRec->getNumOperands() +
2783 OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
2784 const SCEV *Term = getZero(Ty);
2785 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2786 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2787 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2788 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2789 z < ze && !Overflow; ++z) {
2790 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2792 if (LargerThan64Bits)
2793 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2795 Coeff = Coeff1*Coeff2;
2796 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2797 const SCEV *Term1 = AddRec->getOperand(y-z);
2798 const SCEV *Term2 = OtherAddRec->getOperand(z);
2799 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2802 AddRecOps.push_back(Term);
2805 const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
2807 if (Ops.size() == 2) return NewAddRec;
2808 Ops[Idx] = NewAddRec;
2809 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2811 AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
2817 return getMulExpr(Ops);
2819 // Otherwise couldn't fold anything into this recurrence. Move onto the
2823 // Okay, it looks like we really DO need an mul expr. Check to see if we
2824 // already have one, otherwise create a new one.
2825 FoldingSetNodeID ID;
2826 ID.AddInteger(scMulExpr);
2827 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2828 ID.AddPointer(Ops[i]);
2831 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2833 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2834 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2835 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2837 UniqueSCEVs.InsertNode(S, IP);
2839 S->setNoWrapFlags(Flags);
2843 /// Get a canonical unsigned division expression, or something simpler if
2845 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2847 assert(getEffectiveSCEVType(LHS->getType()) ==
2848 getEffectiveSCEVType(RHS->getType()) &&
2849 "SCEVUDivExpr operand types don't match!");
2851 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2852 if (RHSC->getValue()->equalsInt(1))
2853 return LHS; // X udiv 1 --> x
2854 // If the denominator is zero, the result of the udiv is undefined. Don't
2855 // try to analyze it, because the resolution chosen here may differ from
2856 // the resolution chosen in other parts of the compiler.
2857 if (!RHSC->getValue()->isZero()) {
2858 // Determine if the division can be folded into the operands of
2860 // TODO: Generalize this to non-constants by using known-bits information.
2861 Type *Ty = LHS->getType();
2862 unsigned LZ = RHSC->getAPInt().countLeadingZeros();
2863 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2864 // For non-power-of-two values, effectively round the value up to the
2865 // nearest power of two.
2866 if (!RHSC->getAPInt().isPowerOf2())
2868 IntegerType *ExtTy =
2869 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2870 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2871 if (const SCEVConstant *Step =
2872 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2873 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2874 const APInt &StepInt = Step->getAPInt();
2875 const APInt &DivInt = RHSC->getAPInt();
2876 if (!StepInt.urem(DivInt) &&
2877 getZeroExtendExpr(AR, ExtTy) ==
2878 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2879 getZeroExtendExpr(Step, ExtTy),
2880 AR->getLoop(), SCEV::FlagAnyWrap)) {
2881 SmallVector<const SCEV *, 4> Operands;
2882 for (const SCEV *Op : AR->operands())
2883 Operands.push_back(getUDivExpr(Op, RHS));
2884 return getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagNW);
2886 /// Get a canonical UDivExpr for a recurrence.
2887 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2888 // We can currently only fold X%N if X is constant.
2889 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2890 if (StartC && !DivInt.urem(StepInt) &&
2891 getZeroExtendExpr(AR, ExtTy) ==
2892 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2893 getZeroExtendExpr(Step, ExtTy),
2894 AR->getLoop(), SCEV::FlagAnyWrap)) {
2895 const APInt &StartInt = StartC->getAPInt();
2896 const APInt &StartRem = StartInt.urem(StepInt);
2898 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2899 AR->getLoop(), SCEV::FlagNW);
2902 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2903 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2904 SmallVector<const SCEV *, 4> Operands;
2905 for (const SCEV *Op : M->operands())
2906 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2907 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2908 // Find an operand that's safely divisible.
2909 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2910 const SCEV *Op = M->getOperand(i);
2911 const SCEV *Div = getUDivExpr(Op, RHSC);
2912 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2913 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2916 return getMulExpr(Operands);
2920 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2921 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2922 SmallVector<const SCEV *, 4> Operands;
2923 for (const SCEV *Op : A->operands())
2924 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2925 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2927 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2928 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2929 if (isa<SCEVUDivExpr>(Op) ||
2930 getMulExpr(Op, RHS) != A->getOperand(i))
2932 Operands.push_back(Op);
2934 if (Operands.size() == A->getNumOperands())
2935 return getAddExpr(Operands);
2939 // Fold if both operands are constant.
2940 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2941 Constant *LHSCV = LHSC->getValue();
2942 Constant *RHSCV = RHSC->getValue();
2943 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2949 FoldingSetNodeID ID;
2950 ID.AddInteger(scUDivExpr);
2954 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2955 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2957 UniqueSCEVs.InsertNode(S, IP);
2961 static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
2962 APInt A = C1->getAPInt().abs();
2963 APInt B = C2->getAPInt().abs();
2964 uint32_t ABW = A.getBitWidth();
2965 uint32_t BBW = B.getBitWidth();
2972 return APIntOps::GreatestCommonDivisor(A, B);
2975 /// Get a canonical unsigned division expression, or something simpler if
2976 /// possible. There is no representation for an exact udiv in SCEV IR, but we
2977 /// can attempt to remove factors from the LHS and RHS. We can't do this when
2978 /// it's not exact because the udiv may be clearing bits.
2979 const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
2981 // TODO: we could try to find factors in all sorts of things, but for now we
2982 // just deal with u/exact (multiply, constant). See SCEVDivision towards the
2983 // end of this file for inspiration.
2985 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
2986 if (!Mul || !Mul->hasNoUnsignedWrap())
2987 return getUDivExpr(LHS, RHS);
2989 if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
2990 // If the mulexpr multiplies by a constant, then that constant must be the
2991 // first element of the mulexpr.
2992 if (const auto *LHSCst = dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2993 if (LHSCst == RHSCst) {
2994 SmallVector<const SCEV *, 2> Operands;
2995 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2996 return getMulExpr(Operands);
2999 // We can't just assume that LHSCst divides RHSCst cleanly, it could be
3000 // that there's a factor provided by one of the other terms. We need to
3002 APInt Factor = gcd(LHSCst, RHSCst);
3003 if (!Factor.isIntN(1)) {
3005 cast<SCEVConstant>(getConstant(LHSCst->getAPInt().udiv(Factor)));
3007 cast<SCEVConstant>(getConstant(RHSCst->getAPInt().udiv(Factor)));
3008 SmallVector<const SCEV *, 2> Operands;
3009 Operands.push_back(LHSCst);
3010 Operands.append(Mul->op_begin() + 1, Mul->op_end());
3011 LHS = getMulExpr(Operands);
3013 Mul = dyn_cast<SCEVMulExpr>(LHS);
3015 return getUDivExactExpr(LHS, RHS);
3020 for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
3021 if (Mul->getOperand(i) == RHS) {
3022 SmallVector<const SCEV *, 2> Operands;
3023 Operands.append(Mul->op_begin(), Mul->op_begin() + i);
3024 Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
3025 return getMulExpr(Operands);
3029 return getUDivExpr(LHS, RHS);
3032 /// Get an add recurrence expression for the specified loop. Simplify the
3033 /// expression as much as possible.
3034 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
3036 SCEV::NoWrapFlags Flags) {
3037 SmallVector<const SCEV *, 4> Operands;
3038 Operands.push_back(Start);
3039 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
3040 if (StepChrec->getLoop() == L) {
3041 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
3042 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
3045 Operands.push_back(Step);
3046 return getAddRecExpr(Operands, L, Flags);
3049 /// Get an add recurrence expression for the specified loop. Simplify the
3050 /// expression as much as possible.
3052 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
3053 const Loop *L, SCEV::NoWrapFlags Flags) {
3054 if (Operands.size() == 1) return Operands[0];
3056 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
3057 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
3058 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
3059 "SCEVAddRecExpr operand types don't match!");
3060 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
3061 assert(isLoopInvariant(Operands[i], L) &&
3062 "SCEVAddRecExpr operand is not loop-invariant!");
3065 if (Operands.back()->isZero()) {
3066 Operands.pop_back();
3067 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
3070 // It's tempting to want to call getMaxBackedgeTakenCount count here and
3071 // use that information to infer NUW and NSW flags. However, computing a
3072 // BE count requires calling getAddRecExpr, so we may not yet have a
3073 // meaningful BE count at this point (and if we don't, we'd be stuck
3074 // with a SCEVCouldNotCompute as the cached BE count).
3076 Flags = StrengthenNoWrapFlags(this, scAddRecExpr, Operands, Flags);
3078 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
3079 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
3080 const Loop *NestedLoop = NestedAR->getLoop();
3081 if (L->contains(NestedLoop)
3082 ? (L->getLoopDepth() < NestedLoop->getLoopDepth())
3083 : (!NestedLoop->contains(L) &&
3084 DT.dominates(L->getHeader(), NestedLoop->getHeader()))) {
3085 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
3086 NestedAR->op_end());
3087 Operands[0] = NestedAR->getStart();
3088 // AddRecs require their operands be loop-invariant with respect to their
3089 // loops. Don't perform this transformation if it would break this
3091 bool AllInvariant = all_of(
3092 Operands, [&](const SCEV *Op) { return isLoopInvariant(Op, L); });
3095 // Create a recurrence for the outer loop with the same step size.
3097 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
3098 // inner recurrence has the same property.
3099 SCEV::NoWrapFlags OuterFlags =
3100 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
3102 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
3103 AllInvariant = all_of(NestedOperands, [&](const SCEV *Op) {
3104 return isLoopInvariant(Op, NestedLoop);
3108 // Ok, both add recurrences are valid after the transformation.
3110 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
3111 // the outer recurrence has the same property.
3112 SCEV::NoWrapFlags InnerFlags =
3113 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
3114 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
3117 // Reset Operands to its original state.
3118 Operands[0] = NestedAR;
3122 // Okay, it looks like we really DO need an addrec expr. Check to see if we
3123 // already have one, otherwise create a new one.
3124 FoldingSetNodeID ID;
3125 ID.AddInteger(scAddRecExpr);
3126 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
3127 ID.AddPointer(Operands[i]);
3131 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
3133 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
3134 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
3135 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
3136 O, Operands.size(), L);
3137 UniqueSCEVs.InsertNode(S, IP);
3139 S->setNoWrapFlags(Flags);
3144 ScalarEvolution::getGEPExpr(GEPOperator *GEP,
3145 const SmallVectorImpl<const SCEV *> &IndexExprs) {
3146 const SCEV *BaseExpr = getSCEV(GEP->getPointerOperand());
3147 // getSCEV(Base)->getType() has the same address space as Base->getType()
3148 // because SCEV::getType() preserves the address space.
3149 Type *IntPtrTy = getEffectiveSCEVType(BaseExpr->getType());
3150 // FIXME(PR23527): Don't blindly transfer the inbounds flag from the GEP
3151 // instruction to its SCEV, because the Instruction may be guarded by control
3152 // flow and the no-overflow bits may not be valid for the expression in any
3153 // context. This can be fixed similarly to how these flags are handled for
3155 SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW
3156 : SCEV::FlagAnyWrap;
3158 const SCEV *TotalOffset = getZero(IntPtrTy);
3159 // The array size is unimportant. The first thing we do on CurTy is getting
3160 // its element type.
3161 Type *CurTy = ArrayType::get(GEP->getSourceElementType(), 0);
3162 for (const SCEV *IndexExpr : IndexExprs) {
3163 // Compute the (potentially symbolic) offset in bytes for this index.
3164 if (StructType *STy = dyn_cast<StructType>(CurTy)) {
3165 // For a struct, add the member offset.
3166 ConstantInt *Index = cast<SCEVConstant>(IndexExpr)->getValue();
3167 unsigned FieldNo = Index->getZExtValue();
3168 const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
3170 // Add the field offset to the running total offset.
3171 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
3173 // Update CurTy to the type of the field at Index.
3174 CurTy = STy->getTypeAtIndex(Index);
3176 // Update CurTy to its element type.
3177 CurTy = cast<SequentialType>(CurTy)->getElementType();
3178 // For an array, add the element offset, explicitly scaled.
3179 const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, CurTy);
3180 // Getelementptr indices are signed.
3181 IndexExpr = getTruncateOrSignExtend(IndexExpr, IntPtrTy);
3183 // Multiply the index by the element size to compute the element offset.
3184 const SCEV *LocalOffset = getMulExpr(IndexExpr, ElementSize, Wrap);
3186 // Add the element offset to the running total offset.
3187 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
3191 // Add the total offset from all the GEP indices to the base.
3192 return getAddExpr(BaseExpr, TotalOffset, Wrap);
3195 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
3197 SmallVector<const SCEV *, 2> Ops = {LHS, RHS};
3198 return getSMaxExpr(Ops);
3202 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3203 assert(!Ops.empty() && "Cannot get empty smax!");
3204 if (Ops.size() == 1) return Ops[0];
3206 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3207 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3208 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
3209 "SCEVSMaxExpr operand types don't match!");
3212 // Sort by complexity, this groups all similar expression types together.
3213 GroupByComplexity(Ops, &LI);
3215 // If there are any constants, fold them together.
3217 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3219 assert(Idx < Ops.size());
3220 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3221 // We found two constants, fold them together!
3222 ConstantInt *Fold = ConstantInt::get(
3223 getContext(), APIntOps::smax(LHSC->getAPInt(), RHSC->getAPInt()));
3224 Ops[0] = getConstant(Fold);
3225 Ops.erase(Ops.begin()+1); // Erase the folded element
3226 if (Ops.size() == 1) return Ops[0];
3227 LHSC = cast<SCEVConstant>(Ops[0]);
3230 // If we are left with a constant minimum-int, strip it off.
3231 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
3232 Ops.erase(Ops.begin());
3234 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
3235 // If we have an smax with a constant maximum-int, it will always be
3240 if (Ops.size() == 1) return Ops[0];
3243 // Find the first SMax
3244 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
3247 // Check to see if one of the operands is an SMax. If so, expand its operands
3248 // onto our operand list, and recurse to simplify.
3249 if (Idx < Ops.size()) {
3250 bool DeletedSMax = false;
3251 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
3252 Ops.erase(Ops.begin()+Idx);
3253 Ops.append(SMax->op_begin(), SMax->op_end());
3258 return getSMaxExpr(Ops);
3261 // Okay, check to see if the same value occurs in the operand list twice. If
3262 // so, delete one. Since we sorted the list, these values are required to
3264 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3265 // X smax Y smax Y --> X smax Y
3266 // X smax Y --> X, if X is always greater than Y
3267 if (Ops[i] == Ops[i+1] ||
3268 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
3269 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3271 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
3272 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3276 if (Ops.size() == 1) return Ops[0];
3278 assert(!Ops.empty() && "Reduced smax down to nothing!");
3280 // Okay, it looks like we really DO need an smax expr. Check to see if we
3281 // already have one, otherwise create a new one.
3282 FoldingSetNodeID ID;
3283 ID.AddInteger(scSMaxExpr);
3284 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3285 ID.AddPointer(Ops[i]);
3287 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3288 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3289 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3290 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
3292 UniqueSCEVs.InsertNode(S, IP);
3296 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
3298 SmallVector<const SCEV *, 2> Ops = {LHS, RHS};
3299 return getUMaxExpr(Ops);
3303 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3304 assert(!Ops.empty() && "Cannot get empty umax!");
3305 if (Ops.size() == 1) return Ops[0];
3307 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3308 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3309 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
3310 "SCEVUMaxExpr operand types don't match!");
3313 // Sort by complexity, this groups all similar expression types together.
3314 GroupByComplexity(Ops, &LI);
3316 // If there are any constants, fold them together.
3318 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3320 assert(Idx < Ops.size());
3321 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3322 // We found two constants, fold them together!
3323 ConstantInt *Fold = ConstantInt::get(
3324 getContext(), APIntOps::umax(LHSC->getAPInt(), RHSC->getAPInt()));
3325 Ops[0] = getConstant(Fold);
3326 Ops.erase(Ops.begin()+1); // Erase the folded element
3327 if (Ops.size() == 1) return Ops[0];
3328 LHSC = cast<SCEVConstant>(Ops[0]);
3331 // If we are left with a constant minimum-int, strip it off.
3332 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
3333 Ops.erase(Ops.begin());
3335 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
3336 // If we have an umax with a constant maximum-int, it will always be
3341 if (Ops.size() == 1) return Ops[0];
3344 // Find the first UMax
3345 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
3348 // Check to see if one of the operands is a UMax. If so, expand its operands
3349 // onto our operand list, and recurse to simplify.
3350 if (Idx < Ops.size()) {
3351 bool DeletedUMax = false;
3352 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
3353 Ops.erase(Ops.begin()+Idx);
3354 Ops.append(UMax->op_begin(), UMax->op_end());
3359 return getUMaxExpr(Ops);
3362 // Okay, check to see if the same value occurs in the operand list twice. If
3363 // so, delete one. Since we sorted the list, these values are required to
3365 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3366 // X umax Y umax Y --> X umax Y
3367 // X umax Y --> X, if X is always greater than Y
3368 if (Ops[i] == Ops[i+1] ||
3369 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
3370 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3372 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
3373 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3377 if (Ops.size() == 1) return Ops[0];
3379 assert(!Ops.empty() && "Reduced umax down to nothing!");
3381 // Okay, it looks like we really DO need a umax expr. Check to see if we
3382 // already have one, otherwise create a new one.
3383 FoldingSetNodeID ID;
3384 ID.AddInteger(scUMaxExpr);
3385 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3386 ID.AddPointer(Ops[i]);
3388 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3389 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3390 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3391 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
3393 UniqueSCEVs.InsertNode(S, IP);
3397 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
3399 // ~smax(~x, ~y) == smin(x, y).
3400 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3403 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
3405 // ~umax(~x, ~y) == umin(x, y)
3406 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3409 const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
3410 // We can bypass creating a target-independent
3411 // constant expression and then folding it back into a ConstantInt.
3412 // This is just a compile-time optimization.
3413 return getConstant(IntTy, getDataLayout().getTypeAllocSize(AllocTy));
3416 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
3419 // We can bypass creating a target-independent
3420 // constant expression and then folding it back into a ConstantInt.
3421 // This is just a compile-time optimization.
3423 IntTy, getDataLayout().getStructLayout(STy)->getElementOffset(FieldNo));
3426 const SCEV *ScalarEvolution::getUnknown(Value *V) {
3427 // Don't attempt to do anything other than create a SCEVUnknown object
3428 // here. createSCEV only calls getUnknown after checking for all other
3429 // interesting possibilities, and any other code that calls getUnknown
3430 // is doing so in order to hide a value from SCEV canonicalization.
3432 FoldingSetNodeID ID;
3433 ID.AddInteger(scUnknown);
3436 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
3437 assert(cast<SCEVUnknown>(S)->getValue() == V &&
3438 "Stale SCEVUnknown in uniquing map!");
3441 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
3443 FirstUnknown = cast<SCEVUnknown>(S);
3444 UniqueSCEVs.InsertNode(S, IP);
3448 //===----------------------------------------------------------------------===//
3449 // Basic SCEV Analysis and PHI Idiom Recognition Code
3452 /// Test if values of the given type are analyzable within the SCEV
3453 /// framework. This primarily includes integer types, and it can optionally
3454 /// include pointer types if the ScalarEvolution class has access to
3455 /// target-specific information.
3456 bool ScalarEvolution::isSCEVable(Type *Ty) const {
3457 // Integers and pointers are always SCEVable.
3458 return Ty->isIntegerTy() || Ty->isPointerTy();
3461 /// Return the size in bits of the specified type, for which isSCEVable must
3463 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
3464 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3465 return getDataLayout().getTypeSizeInBits(Ty);
3468 /// Return a type with the same bitwidth as the given type and which represents
3469 /// how SCEV will treat the given type, for which isSCEVable must return
3470 /// true. For pointer types, this is the pointer-sized integer type.
3471 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
3472 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3474 if (Ty->isIntegerTy())
3477 // The only other support type is pointer.
3478 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
3479 return getDataLayout().getIntPtrType(Ty);
3482 Type *ScalarEvolution::getWiderType(Type *T1, Type *T2) const {
3483 return getTypeSizeInBits(T1) >= getTypeSizeInBits(T2) ? T1 : T2;
3486 const SCEV *ScalarEvolution::getCouldNotCompute() {
3487 return CouldNotCompute.get();
3490 bool ScalarEvolution::checkValidity(const SCEV *S) const {
3491 bool ContainsNulls = SCEVExprContains(S, [](const SCEV *S) {
3492 auto *SU = dyn_cast<SCEVUnknown>(S);
3493 return SU && SU->getValue() == nullptr;
3496 return !ContainsNulls;
3499 bool ScalarEvolution::containsAddRecurrence(const SCEV *S) {
3500 HasRecMapType::iterator I = HasRecMap.find(S);
3501 if (I != HasRecMap.end())
3504 bool FoundAddRec = SCEVExprContains(S, isa<SCEVAddRecExpr, const SCEV *>);
3505 HasRecMap.insert({S, FoundAddRec});
3509 /// Try to split a SCEVAddExpr into a pair of {SCEV, ConstantInt}.
3510 /// If \p S is a SCEVAddExpr and is composed of a sub SCEV S' and an
3511 /// offset I, then return {S', I}, else return {\p S, nullptr}.
3512 static std::pair<const SCEV *, ConstantInt *> splitAddExpr(const SCEV *S) {
3513 const auto *Add = dyn_cast<SCEVAddExpr>(S);
3515 return {S, nullptr};
3517 if (Add->getNumOperands() != 2)
3518 return {S, nullptr};
3520 auto *ConstOp = dyn_cast<SCEVConstant>(Add->getOperand(0));
3522 return {S, nullptr};
3524 return {Add->getOperand(1), ConstOp->getValue()};
3527 /// Return the ValueOffsetPair set for \p S. \p S can be represented
3528 /// by the value and offset from any ValueOffsetPair in the set.
3529 SetVector<ScalarEvolution::ValueOffsetPair> *
3530 ScalarEvolution::getSCEVValues(const SCEV *S) {
3531 ExprValueMapType::iterator SI = ExprValueMap.find_as(S);
3532 if (SI == ExprValueMap.end())
3535 if (VerifySCEVMap) {
3536 // Check there is no dangling Value in the set returned.
3537 for (const auto &VE : SI->second)
3538 assert(ValueExprMap.count(VE.first));
3544 /// Erase Value from ValueExprMap and ExprValueMap. ValueExprMap.erase(V)
3545 /// cannot be used separately. eraseValueFromMap should be used to remove
3546 /// V from ValueExprMap and ExprValueMap at the same time.
3547 void ScalarEvolution::eraseValueFromMap(Value *V) {
3548 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3549 if (I != ValueExprMap.end()) {
3550 const SCEV *S = I->second;
3551 // Remove {V, 0} from the set of ExprValueMap[S]
3552 if (SetVector<ValueOffsetPair> *SV = getSCEVValues(S))
3553 SV->remove({V, nullptr});
3555 // Remove {V, Offset} from the set of ExprValueMap[Stripped]
3556 const SCEV *Stripped;
3557 ConstantInt *Offset;
3558 std::tie(Stripped, Offset) = splitAddExpr(S);
3559 if (Offset != nullptr) {
3560 if (SetVector<ValueOffsetPair> *SV = getSCEVValues(Stripped))
3561 SV->remove({V, Offset});
3563 ValueExprMap.erase(V);
3567 /// Return an existing SCEV if it exists, otherwise analyze the expression and
3568 /// create a new one.
3569 const SCEV *ScalarEvolution::getSCEV(Value *V) {
3570 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3572 const SCEV *S = getExistingSCEV(V);
3575 // During PHI resolution, it is possible to create two SCEVs for the same
3576 // V, so it is needed to double check whether V->S is inserted into
3577 // ValueExprMap before insert S->{V, 0} into ExprValueMap.
3578 std::pair<ValueExprMapType::iterator, bool> Pair =
3579 ValueExprMap.insert({SCEVCallbackVH(V, this), S});
3581 ExprValueMap[S].insert({V, nullptr});
3583 // If S == Stripped + Offset, add Stripped -> {V, Offset} into
3585 const SCEV *Stripped = S;
3586 ConstantInt *Offset = nullptr;
3587 std::tie(Stripped, Offset) = splitAddExpr(S);
3588 // If stripped is SCEVUnknown, don't bother to save
3589 // Stripped -> {V, offset}. It doesn't simplify and sometimes even
3590 // increase the complexity of the expansion code.
3591 // If V is GetElementPtrInst, don't save Stripped -> {V, offset}
3592 // because it may generate add/sub instead of GEP in SCEV expansion.
3593 if (Offset != nullptr && !isa<SCEVUnknown>(Stripped) &&
3594 !isa<GetElementPtrInst>(V))
3595 ExprValueMap[Stripped].insert({V, Offset});
3601 const SCEV *ScalarEvolution::getExistingSCEV(Value *V) {
3602 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3604 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3605 if (I != ValueExprMap.end()) {
3606 const SCEV *S = I->second;
3607 if (checkValidity(S))
3609 eraseValueFromMap(V);
3610 forgetMemoizedResults(S);
3615 /// Return a SCEV corresponding to -V = -1*V
3617 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V,
3618 SCEV::NoWrapFlags Flags) {
3619 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3621 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
3623 Type *Ty = V->getType();
3624 Ty = getEffectiveSCEVType(Ty);
3626 V, getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))), Flags);
3629 /// Return a SCEV corresponding to ~V = -1-V
3630 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
3631 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3633 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
3635 Type *Ty = V->getType();
3636 Ty = getEffectiveSCEVType(Ty);
3637 const SCEV *AllOnes =
3638 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
3639 return getMinusSCEV(AllOnes, V);
3642 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
3643 SCEV::NoWrapFlags Flags) {
3644 // Fast path: X - X --> 0.
3646 return getZero(LHS->getType());
3648 // We represent LHS - RHS as LHS + (-1)*RHS. This transformation
3649 // makes it so that we cannot make much use of NUW.
3650 auto AddFlags = SCEV::FlagAnyWrap;
3651 const bool RHSIsNotMinSigned =
3652 !getSignedRange(RHS).getSignedMin().isMinSignedValue();
3653 if (maskFlags(Flags, SCEV::FlagNSW) == SCEV::FlagNSW) {
3654 // Let M be the minimum representable signed value. Then (-1)*RHS
3655 // signed-wraps if and only if RHS is M. That can happen even for
3656 // a NSW subtraction because e.g. (-1)*M signed-wraps even though
3657 // -1 - M does not. So to transfer NSW from LHS - RHS to LHS +
3658 // (-1)*RHS, we need to prove that RHS != M.
3660 // If LHS is non-negative and we know that LHS - RHS does not
3661 // signed-wrap, then RHS cannot be M. So we can rule out signed-wrap
3662 // either by proving that RHS > M or that LHS >= 0.
3663 if (RHSIsNotMinSigned || isKnownNonNegative(LHS)) {
3664 AddFlags = SCEV::FlagNSW;
3668 // FIXME: Find a correct way to transfer NSW to (-1)*M when LHS -
3669 // RHS is NSW and LHS >= 0.
3671 // The difficulty here is that the NSW flag may have been proven
3672 // relative to a loop that is to be found in a recurrence in LHS and
3673 // not in RHS. Applying NSW to (-1)*M may then let the NSW have a
3674 // larger scope than intended.
3675 auto NegFlags = RHSIsNotMinSigned ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
3677 return getAddExpr(LHS, getNegativeSCEV(RHS, NegFlags), AddFlags);
3681 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
3682 Type *SrcTy = V->getType();
3683 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3684 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3685 "Cannot truncate or zero extend with non-integer arguments!");
3686 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3687 return V; // No conversion
3688 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3689 return getTruncateExpr(V, Ty);
3690 return getZeroExtendExpr(V, Ty);
3694 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
3696 Type *SrcTy = V->getType();
3697 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3698 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3699 "Cannot truncate or zero extend with non-integer arguments!");
3700 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3701 return V; // No conversion
3702 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3703 return getTruncateExpr(V, Ty);
3704 return getSignExtendExpr(V, Ty);
3708 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
3709 Type *SrcTy = V->getType();
3710 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3711 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3712 "Cannot noop or zero extend with non-integer arguments!");
3713 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3714 "getNoopOrZeroExtend cannot truncate!");
3715 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3716 return V; // No conversion
3717 return getZeroExtendExpr(V, Ty);
3721 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
3722 Type *SrcTy = V->getType();
3723 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3724 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3725 "Cannot noop or sign extend with non-integer arguments!");
3726 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3727 "getNoopOrSignExtend cannot truncate!");
3728 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3729 return V; // No conversion
3730 return getSignExtendExpr(V, Ty);
3734 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
3735 Type *SrcTy = V->getType();
3736 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3737 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3738 "Cannot noop or any extend with non-integer arguments!");
3739 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3740 "getNoopOrAnyExtend cannot truncate!");
3741 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3742 return V; // No conversion
3743 return getAnyExtendExpr(V, Ty);
3747 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
3748 Type *SrcTy = V->getType();
3749 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3750 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3751 "Cannot truncate or noop with non-integer arguments!");
3752 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
3753 "getTruncateOrNoop cannot extend!");
3754 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3755 return V; // No conversion
3756 return getTruncateExpr(V, Ty);
3759 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
3761 const SCEV *PromotedLHS = LHS;
3762 const SCEV *PromotedRHS = RHS;
3764 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3765 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3767 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3769 return getUMaxExpr(PromotedLHS, PromotedRHS);
3772 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
3774 const SCEV *PromotedLHS = LHS;
3775 const SCEV *PromotedRHS = RHS;
3777 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3778 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3780 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3782 return getUMinExpr(PromotedLHS, PromotedRHS);
3785 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
3786 // A pointer operand may evaluate to a nonpointer expression, such as null.
3787 if (!V->getType()->isPointerTy())
3790 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
3791 return getPointerBase(Cast->getOperand());
3792 } else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
3793 const SCEV *PtrOp = nullptr;
3794 for (const SCEV *NAryOp : NAry->operands()) {
3795 if (NAryOp->getType()->isPointerTy()) {
3796 // Cannot find the base of an expression with multiple pointer operands.
3804 return getPointerBase(PtrOp);
3809 /// Push users of the given Instruction onto the given Worklist.
3811 PushDefUseChildren(Instruction *I,
3812 SmallVectorImpl<Instruction *> &Worklist) {
3813 // Push the def-use children onto the Worklist stack.
3814 for (User *U : I->users())
3815 Worklist.push_back(cast<Instruction>(U));
3818 void ScalarEvolution::forgetSymbolicName(Instruction *PN, const SCEV *SymName) {
3819 SmallVector<Instruction *, 16> Worklist;
3820 PushDefUseChildren(PN, Worklist);
3822 SmallPtrSet<Instruction *, 8> Visited;
3824 while (!Worklist.empty()) {
3825 Instruction *I = Worklist.pop_back_val();
3826 if (!Visited.insert(I).second)
3829 auto It = ValueExprMap.find_as(static_cast<Value *>(I));
3830 if (It != ValueExprMap.end()) {
3831 const SCEV *Old = It->second;
3833 // Short-circuit the def-use traversal if the symbolic name
3834 // ceases to appear in expressions.
3835 if (Old != SymName && !hasOperand(Old, SymName))
3838 // SCEVUnknown for a PHI either means that it has an unrecognized
3839 // structure, it's a PHI that's in the progress of being computed
3840 // by createNodeForPHI, or it's a single-value PHI. In the first case,
3841 // additional loop trip count information isn't going to change anything.
3842 // In the second case, createNodeForPHI will perform the necessary
3843 // updates on its own when it gets to that point. In the third, we do
3844 // want to forget the SCEVUnknown.
3845 if (!isa<PHINode>(I) ||
3846 !isa<SCEVUnknown>(Old) ||
3847 (I != PN && Old == SymName)) {
3848 eraseValueFromMap(It->first);
3849 forgetMemoizedResults(Old);
3853 PushDefUseChildren(I, Worklist);
3858 class SCEVInitRewriter : public SCEVRewriteVisitor<SCEVInitRewriter> {
3860 static const SCEV *rewrite(const SCEV *S, const Loop *L,
3861 ScalarEvolution &SE) {
3862 SCEVInitRewriter Rewriter(L, SE);
3863 const SCEV *Result = Rewriter.visit(S);
3864 return Rewriter.isValid() ? Result : SE.getCouldNotCompute();
3867 SCEVInitRewriter(const Loop *L, ScalarEvolution &SE)
3868 : SCEVRewriteVisitor(SE), L(L), Valid(true) {}
3870 const SCEV *visitUnknown(const SCEVUnknown *Expr) {
3871 if (!(SE.getLoopDisposition(Expr, L) == ScalarEvolution::LoopInvariant))
3876 const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
3877 // Only allow AddRecExprs for this loop.
3878 if (Expr->getLoop() == L)
3879 return Expr->getStart();
3884 bool isValid() { return Valid; }
3891 class SCEVShiftRewriter : public SCEVRewriteVisitor<SCEVShiftRewriter> {
3893 static const SCEV *rewrite(const SCEV *S, const Loop *L,
3894 ScalarEvolution &SE) {
3895 SCEVShiftRewriter Rewriter(L, SE);
3896 const SCEV *Result = Rewriter.visit(S);
3897 return Rewriter.isValid() ? Result : SE.getCouldNotCompute();
3900 SCEVShiftRewriter(const Loop *L, ScalarEvolution &SE)
3901 : SCEVRewriteVisitor(SE), L(L), Valid(true) {}
3903 const SCEV *visitUnknown(const SCEVUnknown *Expr) {
3904 // Only allow AddRecExprs for this loop.
3905 if (!(SE.getLoopDisposition(Expr, L) == ScalarEvolution::LoopInvariant))
3910 const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
3911 if (Expr->getLoop() == L && Expr->isAffine())
3912 return SE.getMinusSCEV(Expr, Expr->getStepRecurrence(SE));
3916 bool isValid() { return Valid; }
3922 } // end anonymous namespace
3925 ScalarEvolution::proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR) {
3926 if (!AR->isAffine())
3927 return SCEV::FlagAnyWrap;
3929 typedef OverflowingBinaryOperator OBO;
3930 SCEV::NoWrapFlags Result = SCEV::FlagAnyWrap;
3932 if (!AR->hasNoSignedWrap()) {
3933 ConstantRange AddRecRange = getSignedRange(AR);
3934 ConstantRange IncRange = getSignedRange(AR->getStepRecurrence(*this));
3936 auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
3937 Instruction::Add, IncRange, OBO::NoSignedWrap);
3938 if (NSWRegion.contains(AddRecRange))
3939 Result = ScalarEvolution::setFlags(Result, SCEV::FlagNSW);
3942 if (!AR->hasNoUnsignedWrap()) {
3943 ConstantRange AddRecRange = getUnsignedRange(AR);
3944 ConstantRange IncRange = getUnsignedRange(AR->getStepRecurrence(*this));
3946 auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
3947 Instruction::Add, IncRange, OBO::NoUnsignedWrap);
3948 if (NUWRegion.contains(AddRecRange))
3949 Result = ScalarEvolution::setFlags(Result, SCEV::FlagNUW);
3956 /// Represents an abstract binary operation. This may exist as a
3957 /// normal instruction or constant expression, or may have been
3958 /// derived from an expression tree.
3966 /// Op is set if this BinaryOp corresponds to a concrete LLVM instruction or
3967 /// constant expression.
3970 explicit BinaryOp(Operator *Op)
3971 : Opcode(Op->getOpcode()), LHS(Op->getOperand(0)), RHS(Op->getOperand(1)),
3972 IsNSW(false), IsNUW(false), Op(Op) {
3973 if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(Op)) {
3974 IsNSW = OBO->hasNoSignedWrap();
3975 IsNUW = OBO->hasNoUnsignedWrap();
3979 explicit BinaryOp(unsigned Opcode, Value *LHS, Value *RHS, bool IsNSW = false,
3981 : Opcode(Opcode), LHS(LHS), RHS(RHS), IsNSW(IsNSW), IsNUW(IsNUW),
3987 /// Try to map \p V into a BinaryOp, and return \c None on failure.
3988 static Optional<BinaryOp> MatchBinaryOp(Value *V, DominatorTree &DT) {
3989 auto *Op = dyn_cast<Operator>(V);
3993 // Implementation detail: all the cleverness here should happen without
3994 // creating new SCEV expressions -- our caller knowns tricks to avoid creating
3995 // SCEV expressions when possible, and we should not break that.
3997 switch (Op->getOpcode()) {
3998 case Instruction::Add:
3999 case Instruction::Sub:
4000 case Instruction::Mul:
4001 case Instruction::UDiv:
4002 case Instruction::And:
4003 case Instruction::Or:
4004 case Instruction::AShr:
4005 case Instruction::Shl:
4006 return BinaryOp(Op);
4008 case Instruction::Xor:
4009 if (auto *RHSC = dyn_cast<ConstantInt>(Op->getOperand(1)))
4010 // If the RHS of the xor is a signmask, then this is just an add.
4011 // Instcombine turns add of signmask into xor as a strength reduction step.
4012 if (RHSC->getValue().isSignMask())
4013 return BinaryOp(Instruction::Add, Op->getOperand(0), Op->getOperand(1));
4014 return BinaryOp(Op);
4016 case Instruction::LShr:
4017 // Turn logical shift right of a constant into a unsigned divide.
4018 if (ConstantInt *SA = dyn_cast<ConstantInt>(Op->getOperand(1))) {
4019 uint32_t BitWidth = cast<IntegerType>(Op->getType())->getBitWidth();
4021 // If the shift count is not less than the bitwidth, the result of
4022 // the shift is undefined. Don't try to analyze it, because the
4023 // resolution chosen here may differ from the resolution chosen in
4024 // other parts of the compiler.
4025 if (SA->getValue().ult(BitWidth)) {
4027 ConstantInt::get(SA->getContext(),
4028 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4029 return BinaryOp(Instruction::UDiv, Op->getOperand(0), X);
4032 return BinaryOp(Op);
4034 case Instruction::ExtractValue: {
4035 auto *EVI = cast<ExtractValueInst>(Op);
4036 if (EVI->getNumIndices() != 1 || EVI->getIndices()[0] != 0)
4039 auto *CI = dyn_cast<CallInst>(EVI->getAggregateOperand());
4043 if (auto *F = CI->getCalledFunction())
4044 switch (F->getIntrinsicID()) {
4045 case Intrinsic::sadd_with_overflow:
4046 case Intrinsic::uadd_with_overflow: {
4047 if (!isOverflowIntrinsicNoWrap(cast<IntrinsicInst>(CI), DT))
4048 return BinaryOp(Instruction::Add, CI->getArgOperand(0),
4049 CI->getArgOperand(1));
4051 // Now that we know that all uses of the arithmetic-result component of
4052 // CI are guarded by the overflow check, we can go ahead and pretend
4053 // that the arithmetic is non-overflowing.
4054 if (F->getIntrinsicID() == Intrinsic::sadd_with_overflow)
4055 return BinaryOp(Instruction::Add, CI->getArgOperand(0),
4056 CI->getArgOperand(1), /* IsNSW = */ true,
4057 /* IsNUW = */ false);
4059 return BinaryOp(Instruction::Add, CI->getArgOperand(0),
4060 CI->getArgOperand(1), /* IsNSW = */ false,
4064 case Intrinsic::ssub_with_overflow:
4065 case Intrinsic::usub_with_overflow:
4066 return BinaryOp(Instruction::Sub, CI->getArgOperand(0),
4067 CI->getArgOperand(1));
4069 case Intrinsic::smul_with_overflow:
4070 case Intrinsic::umul_with_overflow:
4071 return BinaryOp(Instruction::Mul, CI->getArgOperand(0),
4072 CI->getArgOperand(1));
4085 const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
4086 const Loop *L = LI.getLoopFor(PN->getParent());
4087 if (!L || L->getHeader() != PN->getParent())
4090 // The loop may have multiple entrances or multiple exits; we can analyze
4091 // this phi as an addrec if it has a unique entry value and a unique
4093 Value *BEValueV = nullptr, *StartValueV = nullptr;
4094 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
4095 Value *V = PN->getIncomingValue(i);
4096 if (L->contains(PN->getIncomingBlock(i))) {
4099 } else if (BEValueV != V) {
4103 } else if (!StartValueV) {
4105 } else if (StartValueV != V) {
4106 StartValueV = nullptr;
4110 if (BEValueV && StartValueV) {
4111 // While we are analyzing this PHI node, handle its value symbolically.
4112 const SCEV *SymbolicName = getUnknown(PN);
4113 assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&
4114 "PHI node already processed?");
4115 ValueExprMap.insert({SCEVCallbackVH(PN, this), SymbolicName});
4117 // Using this symbolic name for the PHI, analyze the value coming around
4119 const SCEV *BEValue = getSCEV(BEValueV);
4121 // NOTE: If BEValue is loop invariant, we know that the PHI node just
4122 // has a special value for the first iteration of the loop.
4124 // If the value coming around the backedge is an add with the symbolic
4125 // value we just inserted, then we found a simple induction variable!
4126 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
4127 // If there is a single occurrence of the symbolic value, replace it
4128 // with a recurrence.
4129 unsigned FoundIndex = Add->getNumOperands();
4130 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
4131 if (Add->getOperand(i) == SymbolicName)
4132 if (FoundIndex == e) {
4137 if (FoundIndex != Add->getNumOperands()) {
4138 // Create an add with everything but the specified operand.
4139 SmallVector<const SCEV *, 8> Ops;
4140 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
4141 if (i != FoundIndex)
4142 Ops.push_back(Add->getOperand(i));
4143 const SCEV *Accum = getAddExpr(Ops);
4145 // This is not a valid addrec if the step amount is varying each
4146 // loop iteration, but is not itself an addrec in this loop.
4147 if (isLoopInvariant(Accum, L) ||
4148 (isa<SCEVAddRecExpr>(Accum) &&
4149 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
4150 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
4152 if (auto BO = MatchBinaryOp(BEValueV, DT)) {
4153 if (BO->Opcode == Instruction::Add && BO->LHS == PN) {
4155 Flags = setFlags(Flags, SCEV::FlagNUW);
4157 Flags = setFlags(Flags, SCEV::FlagNSW);
4159 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
4160 // If the increment is an inbounds GEP, then we know the address
4161 // space cannot be wrapped around. We cannot make any guarantee
4162 // about signed or unsigned overflow because pointers are
4163 // unsigned but we may have a negative index from the base
4164 // pointer. We can guarantee that no unsigned wrap occurs if the
4165 // indices form a positive value.
4166 if (GEP->isInBounds() && GEP->getOperand(0) == PN) {
4167 Flags = setFlags(Flags, SCEV::FlagNW);
4169 const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
4170 if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
4171 Flags = setFlags(Flags, SCEV::FlagNUW);
4174 // We cannot transfer nuw and nsw flags from subtraction
4175 // operations -- sub nuw X, Y is not the same as add nuw X, -Y
4179 const SCEV *StartVal = getSCEV(StartValueV);
4180 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
4182 // Okay, for the entire analysis of this edge we assumed the PHI
4183 // to be symbolic. We now need to go back and purge all of the
4184 // entries for the scalars that use the symbolic expression.
4185 forgetSymbolicName(PN, SymbolicName);
4186 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
4188 // We can add Flags to the post-inc expression only if we
4189 // know that it us *undefined behavior* for BEValueV to
4191 if (auto *BEInst = dyn_cast<Instruction>(BEValueV))
4192 if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L))
4193 (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
4199 // Otherwise, this could be a loop like this:
4200 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
4201 // In this case, j = {1,+,1} and BEValue is j.
4202 // Because the other in-value of i (0) fits the evolution of BEValue
4203 // i really is an addrec evolution.
4205 // We can generalize this saying that i is the shifted value of BEValue
4206 // by one iteration:
4207 // PHI(f(0), f({1,+,1})) --> f({0,+,1})
4208 const SCEV *Shifted = SCEVShiftRewriter::rewrite(BEValue, L, *this);
4209 const SCEV *Start = SCEVInitRewriter::rewrite(Shifted, L, *this);
4210 if (Shifted != getCouldNotCompute() &&
4211 Start != getCouldNotCompute()) {
4212 const SCEV *StartVal = getSCEV(StartValueV);
4213 if (Start == StartVal) {
4214 // Okay, for the entire analysis of this edge we assumed the PHI
4215 // to be symbolic. We now need to go back and purge all of the
4216 // entries for the scalars that use the symbolic expression.
4217 forgetSymbolicName(PN, SymbolicName);
4218 ValueExprMap[SCEVCallbackVH(PN, this)] = Shifted;
4224 // Remove the temporary PHI node SCEV that has been inserted while intending
4225 // to create an AddRecExpr for this PHI node. We can not keep this temporary
4226 // as it will prevent later (possibly simpler) SCEV expressions to be added
4227 // to the ValueExprMap.
4228 eraseValueFromMap(PN);
4234 // Checks if the SCEV S is available at BB. S is considered available at BB
4235 // if S can be materialized at BB without introducing a fault.
4236 static bool IsAvailableOnEntry(const Loop *L, DominatorTree &DT, const SCEV *S,
4238 struct CheckAvailable {
4239 bool TraversalDone = false;
4240 bool Available = true;
4242 const Loop *L = nullptr; // The loop BB is in (can be nullptr)
4243 BasicBlock *BB = nullptr;
4246 CheckAvailable(const Loop *L, BasicBlock *BB, DominatorTree &DT)
4247 : L(L), BB(BB), DT(DT) {}
4249 bool setUnavailable() {
4250 TraversalDone = true;
4255 bool follow(const SCEV *S) {
4256 switch (S->getSCEVType()) {
4257 case scConstant: case scTruncate: case scZeroExtend: case scSignExtend:
4258 case scAddExpr: case scMulExpr: case scUMaxExpr: case scSMaxExpr:
4259 // These expressions are available if their operand(s) is/are.
4262 case scAddRecExpr: {
4263 // We allow add recurrences that are on the loop BB is in, or some
4264 // outer loop. This guarantees availability because the value of the
4265 // add recurrence at BB is simply the "current" value of the induction
4266 // variable. We can relax this in the future; for instance an add
4267 // recurrence on a sibling dominating loop is also available at BB.
4268 const auto *ARLoop = cast<SCEVAddRecExpr>(S)->getLoop();
4269 if (L && (ARLoop == L || ARLoop->contains(L)))
4272 return setUnavailable();
4276 // For SCEVUnknown, we check for simple dominance.
4277 const auto *SU = cast<SCEVUnknown>(S);
4278 Value *V = SU->getValue();
4280 if (isa<Argument>(V))
4283 if (isa<Instruction>(V) && DT.dominates(cast<Instruction>(V), BB))
4286 return setUnavailable();
4290 case scCouldNotCompute:
4291 // We do not try to smart about these at all.
4292 return setUnavailable();
4294 llvm_unreachable("switch should be fully covered!");
4297 bool isDone() { return TraversalDone; }
4300 CheckAvailable CA(L, BB, DT);
4301 SCEVTraversal<CheckAvailable> ST(CA);
4304 return CA.Available;
4307 // Try to match a control flow sequence that branches out at BI and merges back
4308 // at Merge into a "C ? LHS : RHS" select pattern. Return true on a successful
4310 static bool BrPHIToSelect(DominatorTree &DT, BranchInst *BI, PHINode *Merge,
4311 Value *&C, Value *&LHS, Value *&RHS) {
4312 C = BI->getCondition();
4314 BasicBlockEdge LeftEdge(BI->getParent(), BI->getSuccessor(0));
4315 BasicBlockEdge RightEdge(BI->getParent(), BI->getSuccessor(1));
4317 if (!LeftEdge.isSingleEdge())
4320 assert(RightEdge.isSingleEdge() && "Follows from LeftEdge.isSingleEdge()");
4322 Use &LeftUse = Merge->getOperandUse(0);
4323 Use &RightUse = Merge->getOperandUse(1);
4325 if (DT.dominates(LeftEdge, LeftUse) && DT.dominates(RightEdge, RightUse)) {
4331 if (DT.dominates(LeftEdge, RightUse) && DT.dominates(RightEdge, LeftUse)) {
4340 const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
4342 [&](BasicBlock *BB) { return DT.isReachableFromEntry(BB); };
4343 if (PN->getNumIncomingValues() == 2 && all_of(PN->blocks(), IsReachable)) {
4344 const Loop *L = LI.getLoopFor(PN->getParent());
4346 // We don't want to break LCSSA, even in a SCEV expression tree.
4347 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4348 if (LI.getLoopFor(PN->getIncomingBlock(i)) != L)
4353 // br %cond, label %left, label %right
4359 // V = phi [ %x, %left ], [ %y, %right ]
4361 // as "select %cond, %x, %y"
4363 BasicBlock *IDom = DT[PN->getParent()]->getIDom()->getBlock();
4364 assert(IDom && "At least the entry block should dominate PN");
4366 auto *BI = dyn_cast<BranchInst>(IDom->getTerminator());
4367 Value *Cond = nullptr, *LHS = nullptr, *RHS = nullptr;
4369 if (BI && BI->isConditional() &&
4370 BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) &&
4371 IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) &&
4372 IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent()))
4373 return createNodeForSelectOrPHI(PN, Cond, LHS, RHS);
4379 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
4380 if (const SCEV *S = createAddRecFromPHI(PN))
4383 if (const SCEV *S = createNodeFromSelectLikePHI(PN))
4386 // If the PHI has a single incoming value, follow that value, unless the
4387 // PHI's incoming blocks are in a different loop, in which case doing so
4388 // risks breaking LCSSA form. Instcombine would normally zap these, but
4389 // it doesn't have DominatorTree information, so it may miss cases.
4390 if (Value *V = SimplifyInstruction(PN, getDataLayout(), &TLI, &DT, &AC))
4391 if (LI.replacementPreservesLCSSAForm(PN, V))
4394 // If it's not a loop phi, we can't handle it yet.
4395 return getUnknown(PN);
4398 const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I,
4402 // Handle "constant" branch or select. This can occur for instance when a
4403 // loop pass transforms an inner loop and moves on to process the outer loop.
4404 if (auto *CI = dyn_cast<ConstantInt>(Cond))
4405 return getSCEV(CI->isOne() ? TrueVal : FalseVal);
4407 // Try to match some simple smax or umax patterns.
4408 auto *ICI = dyn_cast<ICmpInst>(Cond);
4410 return getUnknown(I);
4412 Value *LHS = ICI->getOperand(0);
4413 Value *RHS = ICI->getOperand(1);
4415 switch (ICI->getPredicate()) {
4416 case ICmpInst::ICMP_SLT:
4417 case ICmpInst::ICMP_SLE:
4418 std::swap(LHS, RHS);
4420 case ICmpInst::ICMP_SGT:
4421 case ICmpInst::ICMP_SGE:
4422 // a >s b ? a+x : b+x -> smax(a, b)+x
4423 // a >s b ? b+x : a+x -> smin(a, b)+x
4424 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
4425 const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), I->getType());
4426 const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), I->getType());
4427 const SCEV *LA = getSCEV(TrueVal);
4428 const SCEV *RA = getSCEV(FalseVal);
4429 const SCEV *LDiff = getMinusSCEV(LA, LS);
4430 const SCEV *RDiff = getMinusSCEV(RA, RS);
4432 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
4433 LDiff = getMinusSCEV(LA, RS);
4434 RDiff = getMinusSCEV(RA, LS);
4436 return getAddExpr(getSMinExpr(LS, RS), LDiff);
4439 case ICmpInst::ICMP_ULT:
4440 case ICmpInst::ICMP_ULE:
4441 std::swap(LHS, RHS);
4443 case ICmpInst::ICMP_UGT:
4444 case ICmpInst::ICMP_UGE:
4445 // a >u b ? a+x : b+x -> umax(a, b)+x
4446 // a >u b ? b+x : a+x -> umin(a, b)+x
4447 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
4448 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4449 const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), I->getType());
4450 const SCEV *LA = getSCEV(TrueVal);
4451 const SCEV *RA = getSCEV(FalseVal);
4452 const SCEV *LDiff = getMinusSCEV(LA, LS);
4453 const SCEV *RDiff = getMinusSCEV(RA, RS);
4455 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
4456 LDiff = getMinusSCEV(LA, RS);
4457 RDiff = getMinusSCEV(RA, LS);
4459 return getAddExpr(getUMinExpr(LS, RS), LDiff);
4462 case ICmpInst::ICMP_NE:
4463 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
4464 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4465 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4466 const SCEV *One = getOne(I->getType());
4467 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4468 const SCEV *LA = getSCEV(TrueVal);
4469 const SCEV *RA = getSCEV(FalseVal);
4470 const SCEV *LDiff = getMinusSCEV(LA, LS);
4471 const SCEV *RDiff = getMinusSCEV(RA, One);
4473 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4476 case ICmpInst::ICMP_EQ:
4477 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
4478 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4479 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4480 const SCEV *One = getOne(I->getType());
4481 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4482 const SCEV *LA = getSCEV(TrueVal);
4483 const SCEV *RA = getSCEV(FalseVal);
4484 const SCEV *LDiff = getMinusSCEV(LA, One);
4485 const SCEV *RDiff = getMinusSCEV(RA, LS);
4487 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4494 return getUnknown(I);
4497 /// Expand GEP instructions into add and multiply operations. This allows them
4498 /// to be analyzed by regular SCEV code.
4499 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
4500 // Don't attempt to analyze GEPs over unsized objects.
4501 if (!GEP->getSourceElementType()->isSized())
4502 return getUnknown(GEP);
4504 SmallVector<const SCEV *, 4> IndexExprs;
4505 for (auto Index = GEP->idx_begin(); Index != GEP->idx_end(); ++Index)
4506 IndexExprs.push_back(getSCEV(*Index));
4507 return getGEPExpr(GEP, IndexExprs);
4510 uint32_t ScalarEvolution::GetMinTrailingZerosImpl(const SCEV *S) {
4511 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4512 return C->getAPInt().countTrailingZeros();
4514 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
4515 return std::min(GetMinTrailingZeros(T->getOperand()),
4516 (uint32_t)getTypeSizeInBits(T->getType()));
4518 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
4519 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4520 return OpRes == getTypeSizeInBits(E->getOperand()->getType())
4521 ? getTypeSizeInBits(E->getType())
4525 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
4526 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4527 return OpRes == getTypeSizeInBits(E->getOperand()->getType())
4528 ? getTypeSizeInBits(E->getType())
4532 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
4533 // The result is the min of all operands results.
4534 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4535 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4536 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4540 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
4541 // The result is the sum of all operands results.
4542 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
4543 uint32_t BitWidth = getTypeSizeInBits(M->getType());
4544 for (unsigned i = 1, e = M->getNumOperands();
4545 SumOpRes != BitWidth && i != e; ++i)
4547 std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)), BitWidth);
4551 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
4552 // The result is the min of all operands results.
4553 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4554 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4555 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4559 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
4560 // The result is the min of all operands results.
4561 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4562 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4563 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4567 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
4568 // The result is the min of all operands results.
4569 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4570 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4571 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4575 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4576 // For a SCEVUnknown, ask ValueTracking.
4577 unsigned BitWidth = getTypeSizeInBits(U->getType());
4578 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4579 computeKnownBits(U->getValue(), Zeros, Ones, getDataLayout(), 0, &AC,
4581 return Zeros.countTrailingOnes();
4588 uint32_t ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
4589 auto I = MinTrailingZerosCache.find(S);
4590 if (I != MinTrailingZerosCache.end())
4593 uint32_t Result = GetMinTrailingZerosImpl(S);
4594 auto InsertPair = MinTrailingZerosCache.insert({S, Result});
4595 assert(InsertPair.second && "Should insert a new key");
4596 return InsertPair.first->second;
4599 /// Helper method to assign a range to V from metadata present in the IR.
4600 static Optional<ConstantRange> GetRangeFromMetadata(Value *V) {
4601 if (Instruction *I = dyn_cast<Instruction>(V))
4602 if (MDNode *MD = I->getMetadata(LLVMContext::MD_range))
4603 return getConstantRangeFromMetadata(*MD);
4608 /// Determine the range for a particular SCEV. If SignHint is
4609 /// HINT_RANGE_UNSIGNED (resp. HINT_RANGE_SIGNED) then getRange prefers ranges
4610 /// with a "cleaner" unsigned (resp. signed) representation.
4612 ScalarEvolution::getRange(const SCEV *S,
4613 ScalarEvolution::RangeSignHint SignHint) {
4614 DenseMap<const SCEV *, ConstantRange> &Cache =
4615 SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED ? UnsignedRanges
4618 // See if we've computed this range already.
4619 DenseMap<const SCEV *, ConstantRange>::iterator I = Cache.find(S);
4620 if (I != Cache.end())
4623 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4624 return setRange(C, SignHint, ConstantRange(C->getAPInt()));
4626 unsigned BitWidth = getTypeSizeInBits(S->getType());
4627 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
4629 // If the value has known zeros, the maximum value will have those known zeros
4631 uint32_t TZ = GetMinTrailingZeros(S);
4633 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED)
4634 ConservativeResult =
4635 ConstantRange(APInt::getMinValue(BitWidth),
4636 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
4638 ConservativeResult = ConstantRange(
4639 APInt::getSignedMinValue(BitWidth),
4640 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
4643 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
4644 ConstantRange X = getRange(Add->getOperand(0), SignHint);
4645 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
4646 X = X.add(getRange(Add->getOperand(i), SignHint));
4647 return setRange(Add, SignHint, ConservativeResult.intersectWith(X));
4650 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
4651 ConstantRange X = getRange(Mul->getOperand(0), SignHint);
4652 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
4653 X = X.multiply(getRange(Mul->getOperand(i), SignHint));
4654 return setRange(Mul, SignHint, ConservativeResult.intersectWith(X));
4657 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
4658 ConstantRange X = getRange(SMax->getOperand(0), SignHint);
4659 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
4660 X = X.smax(getRange(SMax->getOperand(i), SignHint));
4661 return setRange(SMax, SignHint, ConservativeResult.intersectWith(X));
4664 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
4665 ConstantRange X = getRange(UMax->getOperand(0), SignHint);
4666 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
4667 X = X.umax(getRange(UMax->getOperand(i), SignHint));
4668 return setRange(UMax, SignHint, ConservativeResult.intersectWith(X));
4671 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
4672 ConstantRange X = getRange(UDiv->getLHS(), SignHint);
4673 ConstantRange Y = getRange(UDiv->getRHS(), SignHint);
4674 return setRange(UDiv, SignHint,
4675 ConservativeResult.intersectWith(X.udiv(Y)));
4678 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
4679 ConstantRange X = getRange(ZExt->getOperand(), SignHint);
4680 return setRange(ZExt, SignHint,
4681 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
4684 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
4685 ConstantRange X = getRange(SExt->getOperand(), SignHint);
4686 return setRange(SExt, SignHint,
4687 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
4690 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
4691 ConstantRange X = getRange(Trunc->getOperand(), SignHint);
4692 return setRange(Trunc, SignHint,
4693 ConservativeResult.intersectWith(X.truncate(BitWidth)));
4696 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
4697 // If there's no unsigned wrap, the value will never be less than its
4699 if (AddRec->hasNoUnsignedWrap())
4700 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
4701 if (!C->getValue()->isZero())
4702 ConservativeResult = ConservativeResult.intersectWith(
4703 ConstantRange(C->getAPInt(), APInt(BitWidth, 0)));
4705 // If there's no signed wrap, and all the operands have the same sign or
4706 // zero, the value won't ever change sign.
4707 if (AddRec->hasNoSignedWrap()) {
4708 bool AllNonNeg = true;
4709 bool AllNonPos = true;
4710 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4711 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
4712 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
4715 ConservativeResult = ConservativeResult.intersectWith(
4716 ConstantRange(APInt(BitWidth, 0),
4717 APInt::getSignedMinValue(BitWidth)));
4719 ConservativeResult = ConservativeResult.intersectWith(
4720 ConstantRange(APInt::getSignedMinValue(BitWidth),
4721 APInt(BitWidth, 1)));
4724 // TODO: non-affine addrec
4725 if (AddRec->isAffine()) {
4726 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
4727 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
4728 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
4729 auto RangeFromAffine = getRangeForAffineAR(
4730 AddRec->getStart(), AddRec->getStepRecurrence(*this), MaxBECount,
4732 if (!RangeFromAffine.isFullSet())
4733 ConservativeResult =
4734 ConservativeResult.intersectWith(RangeFromAffine);
4736 auto RangeFromFactoring = getRangeViaFactoring(
4737 AddRec->getStart(), AddRec->getStepRecurrence(*this), MaxBECount,
4739 if (!RangeFromFactoring.isFullSet())
4740 ConservativeResult =
4741 ConservativeResult.intersectWith(RangeFromFactoring);
4745 return setRange(AddRec, SignHint, ConservativeResult);
4748 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4749 // Check if the IR explicitly contains !range metadata.
4750 Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
4751 if (MDRange.hasValue())
4752 ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
4754 // Split here to avoid paying the compile-time cost of calling both
4755 // computeKnownBits and ComputeNumSignBits. This restriction can be lifted
4757 const DataLayout &DL = getDataLayout();
4758 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED) {
4759 // For a SCEVUnknown, ask ValueTracking.
4760 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4761 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, &AC, nullptr, &DT);
4762 if (Ones != ~Zeros + 1)
4763 ConservativeResult =
4764 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
4766 assert(SignHint == ScalarEvolution::HINT_RANGE_SIGNED &&
4767 "generalize as needed!");
4768 unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
4770 ConservativeResult = ConservativeResult.intersectWith(
4771 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
4772 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1) + 1));
4775 return setRange(U, SignHint, ConservativeResult);
4778 return setRange(S, SignHint, ConservativeResult);
4781 // Given a StartRange, Step and MaxBECount for an expression compute a range of
4782 // values that the expression can take. Initially, the expression has a value
4783 // from StartRange and then is changed by Step up to MaxBECount times. Signed
4784 // argument defines if we treat Step as signed or unsigned.
4785 static ConstantRange getRangeForAffineARHelper(APInt Step,
4786 ConstantRange StartRange,
4788 unsigned BitWidth, bool Signed) {
4789 // If either Step or MaxBECount is 0, then the expression won't change, and we
4790 // just need to return the initial range.
4791 if (Step == 0 || MaxBECount == 0)
4794 // If we don't know anything about the initial value (i.e. StartRange is
4795 // FullRange), then we don't know anything about the final range either.
4796 // Return FullRange.
4797 if (StartRange.isFullSet())
4798 return ConstantRange(BitWidth, /* isFullSet = */ true);
4800 // If Step is signed and negative, then we use its absolute value, but we also
4801 // note that we're moving in the opposite direction.
4802 bool Descending = Signed && Step.isNegative();
4805 // This is correct even for INT_SMIN. Let's look at i8 to illustrate this:
4806 // abs(INT_SMIN) = abs(-128) = abs(0x80) = -0x80 = 0x80 = 128.
4807 // This equations hold true due to the well-defined wrap-around behavior of
4811 // Check if Offset is more than full span of BitWidth. If it is, the
4812 // expression is guaranteed to overflow.
4813 if (APInt::getMaxValue(StartRange.getBitWidth()).udiv(Step).ult(MaxBECount))
4814 return ConstantRange(BitWidth, /* isFullSet = */ true);
4816 // Offset is by how much the expression can change. Checks above guarantee no
4818 APInt Offset = Step * MaxBECount;
4820 // Minimum value of the final range will match the minimal value of StartRange
4821 // if the expression is increasing and will be decreased by Offset otherwise.
4822 // Maximum value of the final range will match the maximal value of StartRange
4823 // if the expression is decreasing and will be increased by Offset otherwise.
4824 APInt StartLower = StartRange.getLower();
4825 APInt StartUpper = StartRange.getUpper() - 1;
4826 APInt MovedBoundary =
4827 Descending ? (StartLower - Offset) : (StartUpper + Offset);
4829 // It's possible that the new minimum/maximum value will fall into the initial
4830 // range (due to wrap around). This means that the expression can take any
4831 // value in this bitwidth, and we have to return full range.
4832 if (StartRange.contains(MovedBoundary))
4833 return ConstantRange(BitWidth, /* isFullSet = */ true);
4835 APInt NewLower, NewUpper;
4837 NewLower = MovedBoundary;
4838 NewUpper = StartUpper;
4840 NewLower = StartLower;
4841 NewUpper = MovedBoundary;
4844 // If we end up with full range, return a proper full range.
4845 if (NewLower == NewUpper + 1)
4846 return ConstantRange(BitWidth, /* isFullSet = */ true);
4848 // No overflow detected, return [StartLower, StartUpper + Offset + 1) range.
4849 return ConstantRange(NewLower, NewUpper + 1);
4852 ConstantRange ScalarEvolution::getRangeForAffineAR(const SCEV *Start,
4854 const SCEV *MaxBECount,
4855 unsigned BitWidth) {
4856 assert(!isa<SCEVCouldNotCompute>(MaxBECount) &&
4857 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth &&
4860 MaxBECount = getNoopOrZeroExtend(MaxBECount, Start->getType());
4861 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
4862 APInt MaxBECountValue = MaxBECountRange.getUnsignedMax();
4864 // First, consider step signed.
4865 ConstantRange StartSRange = getSignedRange(Start);
4866 ConstantRange StepSRange = getSignedRange(Step);
4868 // If Step can be both positive and negative, we need to find ranges for the
4869 // maximum absolute step values in both directions and union them.
4871 getRangeForAffineARHelper(StepSRange.getSignedMin(), StartSRange,
4872 MaxBECountValue, BitWidth, /* Signed = */ true);
4873 SR = SR.unionWith(getRangeForAffineARHelper(StepSRange.getSignedMax(),
4874 StartSRange, MaxBECountValue,
4875 BitWidth, /* Signed = */ true));
4877 // Next, consider step unsigned.
4878 ConstantRange UR = getRangeForAffineARHelper(
4879 getUnsignedRange(Step).getUnsignedMax(), getUnsignedRange(Start),
4880 MaxBECountValue, BitWidth, /* Signed = */ false);
4882 // Finally, intersect signed and unsigned ranges.
4883 return SR.intersectWith(UR);
4886 ConstantRange ScalarEvolution::getRangeViaFactoring(const SCEV *Start,
4888 const SCEV *MaxBECount,
4889 unsigned BitWidth) {
4890 // RangeOf({C?A:B,+,C?P:Q}) == RangeOf(C?{A,+,P}:{B,+,Q})
4891 // == RangeOf({A,+,P}) union RangeOf({B,+,Q})
4893 struct SelectPattern {
4894 Value *Condition = nullptr;
4898 explicit SelectPattern(ScalarEvolution &SE, unsigned BitWidth,
4900 Optional<unsigned> CastOp;
4901 APInt Offset(BitWidth, 0);
4903 assert(SE.getTypeSizeInBits(S->getType()) == BitWidth &&
4906 // Peel off a constant offset:
4907 if (auto *SA = dyn_cast<SCEVAddExpr>(S)) {
4908 // In the future we could consider being smarter here and handle
4909 // {Start+Step,+,Step} too.
4910 if (SA->getNumOperands() != 2 || !isa<SCEVConstant>(SA->getOperand(0)))
4913 Offset = cast<SCEVConstant>(SA->getOperand(0))->getAPInt();
4914 S = SA->getOperand(1);
4917 // Peel off a cast operation
4918 if (auto *SCast = dyn_cast<SCEVCastExpr>(S)) {
4919 CastOp = SCast->getSCEVType();
4920 S = SCast->getOperand();
4923 using namespace llvm::PatternMatch;
4925 auto *SU = dyn_cast<SCEVUnknown>(S);
4926 const APInt *TrueVal, *FalseVal;
4928 !match(SU->getValue(), m_Select(m_Value(Condition), m_APInt(TrueVal),
4929 m_APInt(FalseVal)))) {
4930 Condition = nullptr;
4934 TrueValue = *TrueVal;
4935 FalseValue = *FalseVal;
4937 // Re-apply the cast we peeled off earlier
4938 if (CastOp.hasValue())
4941 llvm_unreachable("Unknown SCEV cast type!");
4944 TrueValue = TrueValue.trunc(BitWidth);
4945 FalseValue = FalseValue.trunc(BitWidth);
4948 TrueValue = TrueValue.zext(BitWidth);
4949 FalseValue = FalseValue.zext(BitWidth);
4952 TrueValue = TrueValue.sext(BitWidth);
4953 FalseValue = FalseValue.sext(BitWidth);
4957 // Re-apply the constant offset we peeled off earlier
4958 TrueValue += Offset;
4959 FalseValue += Offset;
4962 bool isRecognized() { return Condition != nullptr; }
4965 SelectPattern StartPattern(*this, BitWidth, Start);
4966 if (!StartPattern.isRecognized())
4967 return ConstantRange(BitWidth, /* isFullSet = */ true);
4969 SelectPattern StepPattern(*this, BitWidth, Step);
4970 if (!StepPattern.isRecognized())
4971 return ConstantRange(BitWidth, /* isFullSet = */ true);
4973 if (StartPattern.Condition != StepPattern.Condition) {
4974 // We don't handle this case today; but we could, by considering four
4975 // possibilities below instead of two. I'm not sure if there are cases where
4976 // that will help over what getRange already does, though.
4977 return ConstantRange(BitWidth, /* isFullSet = */ true);
4980 // NB! Calling ScalarEvolution::getConstant is fine, but we should not try to
4981 // construct arbitrary general SCEV expressions here. This function is called
4982 // from deep in the call stack, and calling getSCEV (on a sext instruction,
4983 // say) can end up caching a suboptimal value.
4985 // FIXME: without the explicit `this` receiver below, MSVC errors out with
4986 // C2352 and C2512 (otherwise it isn't needed).
4988 const SCEV *TrueStart = this->getConstant(StartPattern.TrueValue);
4989 const SCEV *TrueStep = this->getConstant(StepPattern.TrueValue);
4990 const SCEV *FalseStart = this->getConstant(StartPattern.FalseValue);
4991 const SCEV *FalseStep = this->getConstant(StepPattern.FalseValue);
4993 ConstantRange TrueRange =
4994 this->getRangeForAffineAR(TrueStart, TrueStep, MaxBECount, BitWidth);
4995 ConstantRange FalseRange =
4996 this->getRangeForAffineAR(FalseStart, FalseStep, MaxBECount, BitWidth);
4998 return TrueRange.unionWith(FalseRange);
5001 SCEV::NoWrapFlags ScalarEvolution::getNoWrapFlagsFromUB(const Value *V) {
5002 if (isa<ConstantExpr>(V)) return SCEV::FlagAnyWrap;
5003 const BinaryOperator *BinOp = cast<BinaryOperator>(V);
5005 // Return early if there are no flags to propagate to the SCEV.
5006 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
5007 if (BinOp->hasNoUnsignedWrap())
5008 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
5009 if (BinOp->hasNoSignedWrap())
5010 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
5011 if (Flags == SCEV::FlagAnyWrap)
5012 return SCEV::FlagAnyWrap;
5014 return isSCEVExprNeverPoison(BinOp) ? Flags : SCEV::FlagAnyWrap;
5017 bool ScalarEvolution::isSCEVExprNeverPoison(const Instruction *I) {
5018 // Here we check that I is in the header of the innermost loop containing I,
5019 // since we only deal with instructions in the loop header. The actual loop we
5020 // need to check later will come from an add recurrence, but getting that
5021 // requires computing the SCEV of the operands, which can be expensive. This
5022 // check we can do cheaply to rule out some cases early.
5023 Loop *InnermostContainingLoop = LI.getLoopFor(I->getParent());
5024 if (InnermostContainingLoop == nullptr ||
5025 InnermostContainingLoop->getHeader() != I->getParent())
5028 // Only proceed if we can prove that I does not yield poison.
5029 if (!isKnownNotFullPoison(I)) return false;
5031 // At this point we know that if I is executed, then it does not wrap
5032 // according to at least one of NSW or NUW. If I is not executed, then we do
5033 // not know if the calculation that I represents would wrap. Multiple
5034 // instructions can map to the same SCEV. If we apply NSW or NUW from I to
5035 // the SCEV, we must guarantee no wrapping for that SCEV also when it is
5036 // derived from other instructions that map to the same SCEV. We cannot make
5037 // that guarantee for cases where I is not executed. So we need to find the
5038 // loop that I is considered in relation to and prove that I is executed for
5039 // every iteration of that loop. That implies that the value that I
5040 // calculates does not wrap anywhere in the loop, so then we can apply the
5041 // flags to the SCEV.
5043 // We check isLoopInvariant to disambiguate in case we are adding recurrences
5044 // from different loops, so that we know which loop to prove that I is
5046 for (unsigned OpIndex = 0; OpIndex < I->getNumOperands(); ++OpIndex) {
5047 // I could be an extractvalue from a call to an overflow intrinsic.
5048 // TODO: We can do better here in some cases.
5049 if (!isSCEVable(I->getOperand(OpIndex)->getType()))
5051 const SCEV *Op = getSCEV(I->getOperand(OpIndex));
5052 if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
5053 bool AllOtherOpsLoopInvariant = true;
5054 for (unsigned OtherOpIndex = 0; OtherOpIndex < I->getNumOperands();
5056 if (OtherOpIndex != OpIndex) {
5057 const SCEV *OtherOp = getSCEV(I->getOperand(OtherOpIndex));
5058 if (!isLoopInvariant(OtherOp, AddRec->getLoop())) {
5059 AllOtherOpsLoopInvariant = false;
5064 if (AllOtherOpsLoopInvariant &&
5065 isGuaranteedToExecuteForEveryIteration(I, AddRec->getLoop()))
5072 bool ScalarEvolution::isAddRecNeverPoison(const Instruction *I, const Loop *L) {
5073 // If we know that \c I can never be poison period, then that's enough.
5074 if (isSCEVExprNeverPoison(I))
5077 // For an add recurrence specifically, we assume that infinite loops without
5078 // side effects are undefined behavior, and then reason as follows:
5080 // If the add recurrence is poison in any iteration, it is poison on all
5081 // future iterations (since incrementing poison yields poison). If the result
5082 // of the add recurrence is fed into the loop latch condition and the loop
5083 // does not contain any throws or exiting blocks other than the latch, we now
5084 // have the ability to "choose" whether the backedge is taken or not (by
5085 // choosing a sufficiently evil value for the poison feeding into the branch)
5086 // for every iteration including and after the one in which \p I first became
5087 // poison. There are two possibilities (let's call the iteration in which \p
5088 // I first became poison as K):
5090 // 1. In the set of iterations including and after K, the loop body executes
5091 // no side effects. In this case executing the backege an infinte number
5092 // of times will yield undefined behavior.
5094 // 2. In the set of iterations including and after K, the loop body executes
5095 // at least one side effect. In this case, that specific instance of side
5096 // effect is control dependent on poison, which also yields undefined
5099 auto *ExitingBB = L->getExitingBlock();
5100 auto *LatchBB = L->getLoopLatch();
5101 if (!ExitingBB || !LatchBB || ExitingBB != LatchBB)
5104 SmallPtrSet<const Instruction *, 16> Pushed;
5105 SmallVector<const Instruction *, 8> PoisonStack;
5107 // We start by assuming \c I, the post-inc add recurrence, is poison. Only
5108 // things that are known to be fully poison under that assumption go on the
5111 PoisonStack.push_back(I);
5113 bool LatchControlDependentOnPoison = false;
5114 while (!PoisonStack.empty() && !LatchControlDependentOnPoison) {
5115 const Instruction *Poison = PoisonStack.pop_back_val();
5117 for (auto *PoisonUser : Poison->users()) {
5118 if (propagatesFullPoison(cast<Instruction>(PoisonUser))) {
5119 if (Pushed.insert(cast<Instruction>(PoisonUser)).second)
5120 PoisonStack.push_back(cast<Instruction>(PoisonUser));
5121 } else if (auto *BI = dyn_cast<BranchInst>(PoisonUser)) {
5122 assert(BI->isConditional() && "Only possibility!");
5123 if (BI->getParent() == LatchBB) {
5124 LatchControlDependentOnPoison = true;
5131 return LatchControlDependentOnPoison && loopHasNoAbnormalExits(L);
5134 ScalarEvolution::LoopProperties
5135 ScalarEvolution::getLoopProperties(const Loop *L) {
5136 typedef ScalarEvolution::LoopProperties LoopProperties;
5138 auto Itr = LoopPropertiesCache.find(L);
5139 if (Itr == LoopPropertiesCache.end()) {
5140 auto HasSideEffects = [](Instruction *I) {
5141 if (auto *SI = dyn_cast<StoreInst>(I))
5142 return !SI->isSimple();
5144 return I->mayHaveSideEffects();
5147 LoopProperties LP = {/* HasNoAbnormalExits */ true,
5148 /*HasNoSideEffects*/ true};
5150 for (auto *BB : L->getBlocks())
5151 for (auto &I : *BB) {
5152 if (!isGuaranteedToTransferExecutionToSuccessor(&I))
5153 LP.HasNoAbnormalExits = false;
5154 if (HasSideEffects(&I))
5155 LP.HasNoSideEffects = false;
5156 if (!LP.HasNoAbnormalExits && !LP.HasNoSideEffects)
5157 break; // We're already as pessimistic as we can get.
5160 auto InsertPair = LoopPropertiesCache.insert({L, LP});
5161 assert(InsertPair.second && "We just checked!");
5162 Itr = InsertPair.first;
5168 const SCEV *ScalarEvolution::createSCEV(Value *V) {
5169 if (!isSCEVable(V->getType()))
5170 return getUnknown(V);
5172 if (Instruction *I = dyn_cast<Instruction>(V)) {
5173 // Don't attempt to analyze instructions in blocks that aren't
5174 // reachable. Such instructions don't matter, and they aren't required
5175 // to obey basic rules for definitions dominating uses which this
5176 // analysis depends on.
5177 if (!DT.isReachableFromEntry(I->getParent()))
5178 return getUnknown(V);
5179 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
5180 return getConstant(CI);
5181 else if (isa<ConstantPointerNull>(V))
5182 return getZero(V->getType());
5183 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
5184 return GA->isInterposable() ? getUnknown(V) : getSCEV(GA->getAliasee());
5185 else if (!isa<ConstantExpr>(V))
5186 return getUnknown(V);
5188 Operator *U = cast<Operator>(V);
5189 if (auto BO = MatchBinaryOp(U, DT)) {
5190 switch (BO->Opcode) {
5191 case Instruction::Add: {
5192 // The simple thing to do would be to just call getSCEV on both operands
5193 // and call getAddExpr with the result. However if we're looking at a
5194 // bunch of things all added together, this can be quite inefficient,
5195 // because it leads to N-1 getAddExpr calls for N ultimate operands.
5196 // Instead, gather up all the operands and make a single getAddExpr call.
5197 // LLVM IR canonical form means we need only traverse the left operands.
5198 SmallVector<const SCEV *, 4> AddOps;
5201 if (auto *OpSCEV = getExistingSCEV(BO->Op)) {
5202 AddOps.push_back(OpSCEV);
5206 // If a NUW or NSW flag can be applied to the SCEV for this
5207 // addition, then compute the SCEV for this addition by itself
5208 // with a separate call to getAddExpr. We need to do that
5209 // instead of pushing the operands of the addition onto AddOps,
5210 // since the flags are only known to apply to this particular
5211 // addition - they may not apply to other additions that can be
5212 // formed with operands from AddOps.
5213 const SCEV *RHS = getSCEV(BO->RHS);
5214 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op);
5215 if (Flags != SCEV::FlagAnyWrap) {
5216 const SCEV *LHS = getSCEV(BO->LHS);
5217 if (BO->Opcode == Instruction::Sub)
5218 AddOps.push_back(getMinusSCEV(LHS, RHS, Flags));
5220 AddOps.push_back(getAddExpr(LHS, RHS, Flags));
5225 if (BO->Opcode == Instruction::Sub)
5226 AddOps.push_back(getNegativeSCEV(getSCEV(BO->RHS)));
5228 AddOps.push_back(getSCEV(BO->RHS));
5230 auto NewBO = MatchBinaryOp(BO->LHS, DT);
5231 if (!NewBO || (NewBO->Opcode != Instruction::Add &&
5232 NewBO->Opcode != Instruction::Sub)) {
5233 AddOps.push_back(getSCEV(BO->LHS));
5239 return getAddExpr(AddOps);
5242 case Instruction::Mul: {
5243 SmallVector<const SCEV *, 4> MulOps;
5246 if (auto *OpSCEV = getExistingSCEV(BO->Op)) {
5247 MulOps.push_back(OpSCEV);
5251 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op);
5252 if (Flags != SCEV::FlagAnyWrap) {
5254 getMulExpr(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags));
5259 MulOps.push_back(getSCEV(BO->RHS));
5260 auto NewBO = MatchBinaryOp(BO->LHS, DT);
5261 if (!NewBO || NewBO->Opcode != Instruction::Mul) {
5262 MulOps.push_back(getSCEV(BO->LHS));
5268 return getMulExpr(MulOps);
5270 case Instruction::UDiv:
5271 return getUDivExpr(getSCEV(BO->LHS), getSCEV(BO->RHS));
5272 case Instruction::Sub: {
5273 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
5275 Flags = getNoWrapFlagsFromUB(BO->Op);
5276 return getMinusSCEV(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags);
5278 case Instruction::And:
5279 // For an expression like x&255 that merely masks off the high bits,
5280 // use zext(trunc(x)) as the SCEV expression.
5281 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) {
5282 if (CI->isNullValue())
5283 return getSCEV(BO->RHS);
5284 if (CI->isAllOnesValue())
5285 return getSCEV(BO->LHS);
5286 const APInt &A = CI->getValue();
5288 // Instcombine's ShrinkDemandedConstant may strip bits out of
5289 // constants, obscuring what would otherwise be a low-bits mask.
5290 // Use computeKnownBits to compute what ShrinkDemandedConstant
5291 // knew about to reconstruct a low-bits mask value.
5292 unsigned LZ = A.countLeadingZeros();
5293 unsigned TZ = A.countTrailingZeros();
5294 unsigned BitWidth = A.getBitWidth();
5295 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
5296 computeKnownBits(BO->LHS, KnownZero, KnownOne, getDataLayout(),
5297 0, &AC, nullptr, &DT);
5299 APInt EffectiveMask =
5300 APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
5301 if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
5302 const SCEV *MulCount = getConstant(APInt::getOneBitSet(BitWidth, TZ));
5303 const SCEV *LHS = getSCEV(BO->LHS);
5304 const SCEV *ShiftedLHS = nullptr;
5305 if (auto *LHSMul = dyn_cast<SCEVMulExpr>(LHS)) {
5306 if (auto *OpC = dyn_cast<SCEVConstant>(LHSMul->getOperand(0))) {
5307 // For an expression like (x * 8) & 8, simplify the multiply.
5308 unsigned MulZeros = OpC->getAPInt().countTrailingZeros();
5309 unsigned GCD = std::min(MulZeros, TZ);
5310 APInt DivAmt = APInt::getOneBitSet(BitWidth, TZ - GCD);
5311 SmallVector<const SCEV*, 4> MulOps;
5312 MulOps.push_back(getConstant(OpC->getAPInt().lshr(GCD)));
5313 MulOps.append(LHSMul->op_begin() + 1, LHSMul->op_end());
5314 auto *NewMul = getMulExpr(MulOps, LHSMul->getNoWrapFlags());
5315 ShiftedLHS = getUDivExpr(NewMul, getConstant(DivAmt));
5319 ShiftedLHS = getUDivExpr(LHS, MulCount);
5322 getTruncateExpr(ShiftedLHS,
5323 IntegerType::get(getContext(), BitWidth - LZ - TZ)),
5324 BO->LHS->getType()),
5330 case Instruction::Or:
5331 // Use ValueTracking to check whether this is actually an add.
5332 if (haveNoCommonBitsSet(BO->LHS, BO->RHS, getDataLayout(), &AC,
5334 // There aren't any common bits set, so the add can't wrap.
5335 auto Flags = SCEV::NoWrapFlags(SCEV::FlagNUW | SCEV::FlagNSW);
5336 return getAddExpr(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags);
5340 case Instruction::Xor:
5341 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) {
5342 // If the RHS of xor is -1, then this is a not operation.
5343 if (CI->isAllOnesValue())
5344 return getNotSCEV(getSCEV(BO->LHS));
5346 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
5347 // This is a variant of the check for xor with -1, and it handles
5348 // the case where instcombine has trimmed non-demanded bits out
5349 // of an xor with -1.
5350 if (auto *LBO = dyn_cast<BinaryOperator>(BO->LHS))
5351 if (ConstantInt *LCI = dyn_cast<ConstantInt>(LBO->getOperand(1)))
5352 if (LBO->getOpcode() == Instruction::And &&
5353 LCI->getValue() == CI->getValue())
5354 if (const SCEVZeroExtendExpr *Z =
5355 dyn_cast<SCEVZeroExtendExpr>(getSCEV(BO->LHS))) {
5356 Type *UTy = BO->LHS->getType();
5357 const SCEV *Z0 = Z->getOperand();
5358 Type *Z0Ty = Z0->getType();
5359 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
5361 // If C is a low-bits mask, the zero extend is serving to
5362 // mask off the high bits. Complement the operand and
5363 // re-apply the zext.
5364 if (CI->getValue().isMask(Z0TySize))
5365 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
5367 // If C is a single bit, it may be in the sign-bit position
5368 // before the zero-extend. In this case, represent the xor
5369 // using an add, which is equivalent, and re-apply the zext.
5370 APInt Trunc = CI->getValue().trunc(Z0TySize);
5371 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
5373 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
5379 case Instruction::Shl:
5380 // Turn shift left of a constant amount into a multiply.
5381 if (ConstantInt *SA = dyn_cast<ConstantInt>(BO->RHS)) {
5382 uint32_t BitWidth = cast<IntegerType>(SA->getType())->getBitWidth();
5384 // If the shift count is not less than the bitwidth, the result of
5385 // the shift is undefined. Don't try to analyze it, because the
5386 // resolution chosen here may differ from the resolution chosen in
5387 // other parts of the compiler.
5388 if (SA->getValue().uge(BitWidth))
5391 // It is currently not resolved how to interpret NSW for left
5392 // shift by BitWidth - 1, so we avoid applying flags in that
5393 // case. Remove this check (or this comment) once the situation
5395 // http://lists.llvm.org/pipermail/llvm-dev/2015-April/084195.html
5396 // and http://reviews.llvm.org/D8890 .
5397 auto Flags = SCEV::FlagAnyWrap;
5398 if (BO->Op && SA->getValue().ult(BitWidth - 1))
5399 Flags = getNoWrapFlagsFromUB(BO->Op);
5401 Constant *X = ConstantInt::get(getContext(),
5402 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
5403 return getMulExpr(getSCEV(BO->LHS), getSCEV(X), Flags);
5407 case Instruction::AShr:
5408 // AShr X, C, where C is a constant.
5409 ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS);
5413 Type *OuterTy = BO->LHS->getType();
5414 uint64_t BitWidth = getTypeSizeInBits(OuterTy);
5415 // If the shift count is not less than the bitwidth, the result of
5416 // the shift is undefined. Don't try to analyze it, because the
5417 // resolution chosen here may differ from the resolution chosen in
5418 // other parts of the compiler.
5419 if (CI->getValue().uge(BitWidth))
5422 if (CI->isNullValue())
5423 return getSCEV(BO->LHS); // shift by zero --> noop
5425 uint64_t AShrAmt = CI->getZExtValue();
5426 Type *TruncTy = IntegerType::get(getContext(), BitWidth - AShrAmt);
5428 Operator *L = dyn_cast<Operator>(BO->LHS);
5429 if (L && L->getOpcode() == Instruction::Shl) {
5432 // Both n and m are constant.
5434 const SCEV *ShlOp0SCEV = getSCEV(L->getOperand(0));
5435 if (L->getOperand(1) == BO->RHS)
5436 // For a two-shift sext-inreg, i.e. n = m,
5437 // use sext(trunc(x)) as the SCEV expression.
5438 return getSignExtendExpr(
5439 getTruncateExpr(ShlOp0SCEV, TruncTy), OuterTy);
5441 ConstantInt *ShlAmtCI = dyn_cast<ConstantInt>(L->getOperand(1));
5442 if (ShlAmtCI && ShlAmtCI->getValue().ult(BitWidth)) {
5443 uint64_t ShlAmt = ShlAmtCI->getZExtValue();
5444 if (ShlAmt > AShrAmt) {
5445 // When n > m, use sext(mul(trunc(x), 2^(n-m)))) as the SCEV
5446 // expression. We already checked that ShlAmt < BitWidth, so
5447 // the multiplier, 1 << (ShlAmt - AShrAmt), fits into TruncTy as
5448 // ShlAmt - AShrAmt < Amt.
5449 APInt Mul = APInt::getOneBitSet(BitWidth - AShrAmt,
5451 return getSignExtendExpr(
5452 getMulExpr(getTruncateExpr(ShlOp0SCEV, TruncTy),
5453 getConstant(Mul)), OuterTy);
5461 switch (U->getOpcode()) {
5462 case Instruction::Trunc:
5463 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
5465 case Instruction::ZExt:
5466 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
5468 case Instruction::SExt:
5469 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
5471 case Instruction::BitCast:
5472 // BitCasts are no-op casts so we just eliminate the cast.
5473 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
5474 return getSCEV(U->getOperand(0));
5477 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
5478 // lead to pointer expressions which cannot safely be expanded to GEPs,
5479 // because ScalarEvolution doesn't respect the GEP aliasing rules when
5480 // simplifying integer expressions.
5482 case Instruction::GetElementPtr:
5483 return createNodeForGEP(cast<GEPOperator>(U));
5485 case Instruction::PHI:
5486 return createNodeForPHI(cast<PHINode>(U));
5488 case Instruction::Select:
5489 // U can also be a select constant expr, which let fall through. Since
5490 // createNodeForSelect only works for a condition that is an `ICmpInst`, and
5491 // constant expressions cannot have instructions as operands, we'd have
5492 // returned getUnknown for a select constant expressions anyway.
5493 if (isa<Instruction>(U))
5494 return createNodeForSelectOrPHI(cast<Instruction>(U), U->getOperand(0),
5495 U->getOperand(1), U->getOperand(2));
5498 case Instruction::Call:
5499 case Instruction::Invoke:
5500 if (Value *RV = CallSite(U).getReturnedArgOperand())
5505 return getUnknown(V);
5510 //===----------------------------------------------------------------------===//
5511 // Iteration Count Computation Code
5514 static unsigned getConstantTripCount(const SCEVConstant *ExitCount) {
5518 ConstantInt *ExitConst = ExitCount->getValue();
5520 // Guard against huge trip counts.
5521 if (ExitConst->getValue().getActiveBits() > 32)
5524 // In case of integer overflow, this returns 0, which is correct.
5525 return ((unsigned)ExitConst->getZExtValue()) + 1;
5528 unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L) {
5529 if (BasicBlock *ExitingBB = L->getExitingBlock())
5530 return getSmallConstantTripCount(L, ExitingBB);
5532 // No trip count information for multiple exits.
5536 unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L,
5537 BasicBlock *ExitingBlock) {
5538 assert(ExitingBlock && "Must pass a non-null exiting block!");
5539 assert(L->isLoopExiting(ExitingBlock) &&
5540 "Exiting block must actually branch out of the loop!");
5541 const SCEVConstant *ExitCount =
5542 dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
5543 return getConstantTripCount(ExitCount);
5546 unsigned ScalarEvolution::getSmallConstantMaxTripCount(const Loop *L) {
5547 const auto *MaxExitCount =
5548 dyn_cast<SCEVConstant>(getMaxBackedgeTakenCount(L));
5549 return getConstantTripCount(MaxExitCount);
5552 unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L) {
5553 if (BasicBlock *ExitingBB = L->getExitingBlock())
5554 return getSmallConstantTripMultiple(L, ExitingBB);
5556 // No trip multiple information for multiple exits.
5560 /// Returns the largest constant divisor of the trip count of this loop as a
5561 /// normal unsigned value, if possible. This means that the actual trip count is
5562 /// always a multiple of the returned value (don't forget the trip count could
5563 /// very well be zero as well!).
5565 /// Returns 1 if the trip count is unknown or not guaranteed to be the
5566 /// multiple of a constant (which is also the case if the trip count is simply
5567 /// constant, use getSmallConstantTripCount for that case), Will also return 1
5568 /// if the trip count is very large (>= 2^32).
5570 /// As explained in the comments for getSmallConstantTripCount, this assumes
5571 /// that control exits the loop via ExitingBlock.
5573 ScalarEvolution::getSmallConstantTripMultiple(const Loop *L,
5574 BasicBlock *ExitingBlock) {
5575 assert(ExitingBlock && "Must pass a non-null exiting block!");
5576 assert(L->isLoopExiting(ExitingBlock) &&
5577 "Exiting block must actually branch out of the loop!");
5578 const SCEV *ExitCount = getExitCount(L, ExitingBlock);
5579 if (ExitCount == getCouldNotCompute())
5582 // Get the trip count from the BE count by adding 1.
5583 const SCEV *TCExpr = getAddExpr(ExitCount, getOne(ExitCount->getType()));
5585 const SCEVConstant *TC = dyn_cast<SCEVConstant>(TCExpr);
5587 // Attempt to factor more general cases. Returns the greatest power of
5588 // two divisor. If overflow happens, the trip count expression is still
5589 // divisible by the greatest power of 2 divisor returned.
5590 return 1U << std::min((uint32_t)31, GetMinTrailingZeros(TCExpr));
5592 ConstantInt *Result = TC->getValue();
5594 // Guard against huge trip counts (this requires checking
5595 // for zero to handle the case where the trip count == -1 and the
5597 if (!Result || Result->getValue().getActiveBits() > 32 ||
5598 Result->getValue().getActiveBits() == 0)
5601 return (unsigned)Result->getZExtValue();
5604 /// Get the expression for the number of loop iterations for which this loop is
5605 /// guaranteed not to exit via ExitingBlock. Otherwise return
5606 /// SCEVCouldNotCompute.
5607 const SCEV *ScalarEvolution::getExitCount(const Loop *L,
5608 BasicBlock *ExitingBlock) {
5609 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
5613 ScalarEvolution::getPredicatedBackedgeTakenCount(const Loop *L,
5614 SCEVUnionPredicate &Preds) {
5615 return getPredicatedBackedgeTakenInfo(L).getExact(this, &Preds);
5618 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
5619 return getBackedgeTakenInfo(L).getExact(this);
5622 /// Similar to getBackedgeTakenCount, except return the least SCEV value that is
5623 /// known never to be less than the actual backedge taken count.
5624 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
5625 return getBackedgeTakenInfo(L).getMax(this);
5628 bool ScalarEvolution::isBackedgeTakenCountMaxOrZero(const Loop *L) {
5629 return getBackedgeTakenInfo(L).isMaxOrZero(this);
5632 /// Push PHI nodes in the header of the given loop onto the given Worklist.
5634 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
5635 BasicBlock *Header = L->getHeader();
5637 // Push all Loop-header PHIs onto the Worklist stack.
5638 for (BasicBlock::iterator I = Header->begin();
5639 PHINode *PN = dyn_cast<PHINode>(I); ++I)
5640 Worklist.push_back(PN);
5643 const ScalarEvolution::BackedgeTakenInfo &
5644 ScalarEvolution::getPredicatedBackedgeTakenInfo(const Loop *L) {
5645 auto &BTI = getBackedgeTakenInfo(L);
5646 if (BTI.hasFullInfo())
5649 auto Pair = PredicatedBackedgeTakenCounts.insert({L, BackedgeTakenInfo()});
5652 return Pair.first->second;
5654 BackedgeTakenInfo Result =
5655 computeBackedgeTakenCount(L, /*AllowPredicates=*/true);
5657 return PredicatedBackedgeTakenCounts.find(L)->second = std::move(Result);
5660 const ScalarEvolution::BackedgeTakenInfo &
5661 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
5662 // Initially insert an invalid entry for this loop. If the insertion
5663 // succeeds, proceed to actually compute a backedge-taken count and
5664 // update the value. The temporary CouldNotCompute value tells SCEV
5665 // code elsewhere that it shouldn't attempt to request a new
5666 // backedge-taken count, which could result in infinite recursion.
5667 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
5668 BackedgeTakenCounts.insert({L, BackedgeTakenInfo()});
5670 return Pair.first->second;
5672 // computeBackedgeTakenCount may allocate memory for its result. Inserting it
5673 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
5674 // must be cleared in this scope.
5675 BackedgeTakenInfo Result = computeBackedgeTakenCount(L);
5677 if (Result.getExact(this) != getCouldNotCompute()) {
5678 assert(isLoopInvariant(Result.getExact(this), L) &&
5679 isLoopInvariant(Result.getMax(this), L) &&
5680 "Computed backedge-taken count isn't loop invariant for loop!");
5681 ++NumTripCountsComputed;
5683 else if (Result.getMax(this) == getCouldNotCompute() &&
5684 isa<PHINode>(L->getHeader()->begin())) {
5685 // Only count loops that have phi nodes as not being computable.
5686 ++NumTripCountsNotComputed;
5689 // Now that we know more about the trip count for this loop, forget any
5690 // existing SCEV values for PHI nodes in this loop since they are only
5691 // conservative estimates made without the benefit of trip count
5692 // information. This is similar to the code in forgetLoop, except that
5693 // it handles SCEVUnknown PHI nodes specially.
5694 if (Result.hasAnyInfo()) {
5695 SmallVector<Instruction *, 16> Worklist;
5696 PushLoopPHIs(L, Worklist);
5698 SmallPtrSet<Instruction *, 8> Visited;
5699 while (!Worklist.empty()) {
5700 Instruction *I = Worklist.pop_back_val();
5701 if (!Visited.insert(I).second)
5704 ValueExprMapType::iterator It =
5705 ValueExprMap.find_as(static_cast<Value *>(I));
5706 if (It != ValueExprMap.end()) {
5707 const SCEV *Old = It->second;
5709 // SCEVUnknown for a PHI either means that it has an unrecognized
5710 // structure, or it's a PHI that's in the progress of being computed
5711 // by createNodeForPHI. In the former case, additional loop trip
5712 // count information isn't going to change anything. In the later
5713 // case, createNodeForPHI will perform the necessary updates on its
5714 // own when it gets to that point.
5715 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
5716 eraseValueFromMap(It->first);
5717 forgetMemoizedResults(Old);
5719 if (PHINode *PN = dyn_cast<PHINode>(I))
5720 ConstantEvolutionLoopExitValue.erase(PN);
5723 PushDefUseChildren(I, Worklist);
5727 // Re-lookup the insert position, since the call to
5728 // computeBackedgeTakenCount above could result in a
5729 // recusive call to getBackedgeTakenInfo (on a different
5730 // loop), which would invalidate the iterator computed
5732 return BackedgeTakenCounts.find(L)->second = std::move(Result);
5735 void ScalarEvolution::forgetLoop(const Loop *L) {
5736 // Drop any stored trip count value.
5737 auto RemoveLoopFromBackedgeMap =
5738 [L](DenseMap<const Loop *, BackedgeTakenInfo> &Map) {
5739 auto BTCPos = Map.find(L);
5740 if (BTCPos != Map.end()) {
5741 BTCPos->second.clear();
5746 RemoveLoopFromBackedgeMap(BackedgeTakenCounts);
5747 RemoveLoopFromBackedgeMap(PredicatedBackedgeTakenCounts);
5749 // Drop information about expressions based on loop-header PHIs.
5750 SmallVector<Instruction *, 16> Worklist;
5751 PushLoopPHIs(L, Worklist);
5753 SmallPtrSet<Instruction *, 8> Visited;
5754 while (!Worklist.empty()) {
5755 Instruction *I = Worklist.pop_back_val();
5756 if (!Visited.insert(I).second)
5759 ValueExprMapType::iterator It =
5760 ValueExprMap.find_as(static_cast<Value *>(I));
5761 if (It != ValueExprMap.end()) {
5762 eraseValueFromMap(It->first);
5763 forgetMemoizedResults(It->second);
5764 if (PHINode *PN = dyn_cast<PHINode>(I))
5765 ConstantEvolutionLoopExitValue.erase(PN);
5768 PushDefUseChildren(I, Worklist);
5771 // Forget all contained loops too, to avoid dangling entries in the
5772 // ValuesAtScopes map.
5776 LoopPropertiesCache.erase(L);
5779 void ScalarEvolution::forgetValue(Value *V) {
5780 Instruction *I = dyn_cast<Instruction>(V);
5783 // Drop information about expressions based on loop-header PHIs.
5784 SmallVector<Instruction *, 16> Worklist;
5785 Worklist.push_back(I);
5787 SmallPtrSet<Instruction *, 8> Visited;
5788 while (!Worklist.empty()) {
5789 I = Worklist.pop_back_val();
5790 if (!Visited.insert(I).second)
5793 ValueExprMapType::iterator It =
5794 ValueExprMap.find_as(static_cast<Value *>(I));
5795 if (It != ValueExprMap.end()) {
5796 eraseValueFromMap(It->first);
5797 forgetMemoizedResults(It->second);
5798 if (PHINode *PN = dyn_cast<PHINode>(I))
5799 ConstantEvolutionLoopExitValue.erase(PN);
5802 PushDefUseChildren(I, Worklist);
5806 /// Get the exact loop backedge taken count considering all loop exits. A
5807 /// computable result can only be returned for loops with a single exit.
5808 /// Returning the minimum taken count among all exits is incorrect because one
5809 /// of the loop's exit limit's may have been skipped. howFarToZero assumes that
5810 /// the limit of each loop test is never skipped. This is a valid assumption as
5811 /// long as the loop exits via that test. For precise results, it is the
5812 /// caller's responsibility to specify the relevant loop exit using
5813 /// getExact(ExitingBlock, SE).
5815 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE,
5816 SCEVUnionPredicate *Preds) const {
5817 // If any exits were not computable, the loop is not computable.
5818 if (!isComplete() || ExitNotTaken.empty())
5819 return SE->getCouldNotCompute();
5821 const SCEV *BECount = nullptr;
5822 for (auto &ENT : ExitNotTaken) {
5823 assert(ENT.ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
5826 BECount = ENT.ExactNotTaken;
5827 else if (BECount != ENT.ExactNotTaken)
5828 return SE->getCouldNotCompute();
5829 if (Preds && !ENT.hasAlwaysTruePredicate())
5830 Preds->add(ENT.Predicate.get());
5832 assert((Preds || ENT.hasAlwaysTruePredicate()) &&
5833 "Predicate should be always true!");
5836 assert(BECount && "Invalid not taken count for loop exit");
5840 /// Get the exact not taken count for this loop exit.
5842 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
5843 ScalarEvolution *SE) const {
5844 for (auto &ENT : ExitNotTaken)
5845 if (ENT.ExitingBlock == ExitingBlock && ENT.hasAlwaysTruePredicate())
5846 return ENT.ExactNotTaken;
5848 return SE->getCouldNotCompute();
5851 /// getMax - Get the max backedge taken count for the loop.
5853 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
5854 auto PredicateNotAlwaysTrue = [](const ExitNotTakenInfo &ENT) {
5855 return !ENT.hasAlwaysTruePredicate();
5858 if (any_of(ExitNotTaken, PredicateNotAlwaysTrue) || !getMax())
5859 return SE->getCouldNotCompute();
5864 bool ScalarEvolution::BackedgeTakenInfo::isMaxOrZero(ScalarEvolution *SE) const {
5865 auto PredicateNotAlwaysTrue = [](const ExitNotTakenInfo &ENT) {
5866 return !ENT.hasAlwaysTruePredicate();
5868 return MaxOrZero && !any_of(ExitNotTaken, PredicateNotAlwaysTrue);
5871 bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S,
5872 ScalarEvolution *SE) const {
5873 if (getMax() && getMax() != SE->getCouldNotCompute() &&
5874 SE->hasOperand(getMax(), S))
5877 for (auto &ENT : ExitNotTaken)
5878 if (ENT.ExactNotTaken != SE->getCouldNotCompute() &&
5879 SE->hasOperand(ENT.ExactNotTaken, S))
5885 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
5886 /// computable exit into a persistent ExitNotTakenInfo array.
5887 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
5888 SmallVectorImpl<ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo>
5890 bool Complete, const SCEV *MaxCount, bool MaxOrZero)
5891 : MaxAndComplete(MaxCount, Complete), MaxOrZero(MaxOrZero) {
5892 typedef ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo EdgeExitInfo;
5893 ExitNotTaken.reserve(ExitCounts.size());
5895 ExitCounts.begin(), ExitCounts.end(), std::back_inserter(ExitNotTaken),
5896 [&](const EdgeExitInfo &EEI) {
5897 BasicBlock *ExitBB = EEI.first;
5898 const ExitLimit &EL = EEI.second;
5899 if (EL.Predicates.empty())
5900 return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken, nullptr);
5902 std::unique_ptr<SCEVUnionPredicate> Predicate(new SCEVUnionPredicate);
5903 for (auto *Pred : EL.Predicates)
5904 Predicate->add(Pred);
5906 return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken, std::move(Predicate));
5910 /// Invalidate this result and free the ExitNotTakenInfo array.
5911 void ScalarEvolution::BackedgeTakenInfo::clear() {
5912 ExitNotTaken.clear();
5915 /// Compute the number of times the backedge of the specified loop will execute.
5916 ScalarEvolution::BackedgeTakenInfo
5917 ScalarEvolution::computeBackedgeTakenCount(const Loop *L,
5918 bool AllowPredicates) {
5919 SmallVector<BasicBlock *, 8> ExitingBlocks;
5920 L->getExitingBlocks(ExitingBlocks);
5922 typedef ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo EdgeExitInfo;
5924 SmallVector<EdgeExitInfo, 4> ExitCounts;
5925 bool CouldComputeBECount = true;
5926 BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
5927 const SCEV *MustExitMaxBECount = nullptr;
5928 const SCEV *MayExitMaxBECount = nullptr;
5929 bool MustExitMaxOrZero = false;
5931 // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
5932 // and compute maxBECount.
5933 // Do a union of all the predicates here.
5934 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
5935 BasicBlock *ExitBB = ExitingBlocks[i];
5936 ExitLimit EL = computeExitLimit(L, ExitBB, AllowPredicates);
5938 assert((AllowPredicates || EL.Predicates.empty()) &&
5939 "Predicated exit limit when predicates are not allowed!");
5941 // 1. For each exit that can be computed, add an entry to ExitCounts.
5942 // CouldComputeBECount is true only if all exits can be computed.
5943 if (EL.ExactNotTaken == getCouldNotCompute())
5944 // We couldn't compute an exact value for this exit, so
5945 // we won't be able to compute an exact value for the loop.
5946 CouldComputeBECount = false;
5948 ExitCounts.emplace_back(ExitBB, EL);
5950 // 2. Derive the loop's MaxBECount from each exit's max number of
5951 // non-exiting iterations. Partition the loop exits into two kinds:
5952 // LoopMustExits and LoopMayExits.
5954 // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
5955 // is a LoopMayExit. If any computable LoopMustExit is found, then
5956 // MaxBECount is the minimum EL.MaxNotTaken of computable
5957 // LoopMustExits. Otherwise, MaxBECount is conservatively the maximum
5958 // EL.MaxNotTaken, where CouldNotCompute is considered greater than any
5959 // computable EL.MaxNotTaken.
5960 if (EL.MaxNotTaken != getCouldNotCompute() && Latch &&
5961 DT.dominates(ExitBB, Latch)) {
5962 if (!MustExitMaxBECount) {
5963 MustExitMaxBECount = EL.MaxNotTaken;
5964 MustExitMaxOrZero = EL.MaxOrZero;
5966 MustExitMaxBECount =
5967 getUMinFromMismatchedTypes(MustExitMaxBECount, EL.MaxNotTaken);
5969 } else if (MayExitMaxBECount != getCouldNotCompute()) {
5970 if (!MayExitMaxBECount || EL.MaxNotTaken == getCouldNotCompute())
5971 MayExitMaxBECount = EL.MaxNotTaken;
5974 getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.MaxNotTaken);
5978 const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
5979 (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
5980 // The loop backedge will be taken the maximum or zero times if there's
5981 // a single exit that must be taken the maximum or zero times.
5982 bool MaxOrZero = (MustExitMaxOrZero && ExitingBlocks.size() == 1);
5983 return BackedgeTakenInfo(std::move(ExitCounts), CouldComputeBECount,
5984 MaxBECount, MaxOrZero);
5987 ScalarEvolution::ExitLimit
5988 ScalarEvolution::computeExitLimit(const Loop *L, BasicBlock *ExitingBlock,
5989 bool AllowPredicates) {
5991 // Okay, we've chosen an exiting block. See what condition causes us to exit
5992 // at this block and remember the exit block and whether all other targets
5993 // lead to the loop header.
5994 bool MustExecuteLoopHeader = true;
5995 BasicBlock *Exit = nullptr;
5996 for (auto *SBB : successors(ExitingBlock))
5997 if (!L->contains(SBB)) {
5998 if (Exit) // Multiple exit successors.
5999 return getCouldNotCompute();
6001 } else if (SBB != L->getHeader()) {
6002 MustExecuteLoopHeader = false;
6005 // At this point, we know we have a conditional branch that determines whether
6006 // the loop is exited. However, we don't know if the branch is executed each
6007 // time through the loop. If not, then the execution count of the branch will
6008 // not be equal to the trip count of the loop.
6010 // Currently we check for this by checking to see if the Exit branch goes to
6011 // the loop header. If so, we know it will always execute the same number of
6012 // times as the loop. We also handle the case where the exit block *is* the
6013 // loop header. This is common for un-rotated loops.
6015 // If both of those tests fail, walk up the unique predecessor chain to the
6016 // header, stopping if there is an edge that doesn't exit the loop. If the
6017 // header is reached, the execution count of the branch will be equal to the
6018 // trip count of the loop.
6020 // More extensive analysis could be done to handle more cases here.
6022 if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
6023 // The simple checks failed, try climbing the unique predecessor chain
6024 // up to the header.
6026 for (BasicBlock *BB = ExitingBlock; BB; ) {
6027 BasicBlock *Pred = BB->getUniquePredecessor();
6029 return getCouldNotCompute();
6030 TerminatorInst *PredTerm = Pred->getTerminator();
6031 for (const BasicBlock *PredSucc : PredTerm->successors()) {
6034 // If the predecessor has a successor that isn't BB and isn't
6035 // outside the loop, assume the worst.
6036 if (L->contains(PredSucc))
6037 return getCouldNotCompute();
6039 if (Pred == L->getHeader()) {
6046 return getCouldNotCompute();
6049 bool IsOnlyExit = (L->getExitingBlock() != nullptr);
6050 TerminatorInst *Term = ExitingBlock->getTerminator();
6051 if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
6052 assert(BI->isConditional() && "If unconditional, it can't be in loop!");
6053 // Proceed to the next level to examine the exit condition expression.
6054 return computeExitLimitFromCond(
6055 L, BI->getCondition(), BI->getSuccessor(0), BI->getSuccessor(1),
6056 /*ControlsExit=*/IsOnlyExit, AllowPredicates);
6059 if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
6060 return computeExitLimitFromSingleExitSwitch(L, SI, Exit,
6061 /*ControlsExit=*/IsOnlyExit);
6063 return getCouldNotCompute();
6066 ScalarEvolution::ExitLimit
6067 ScalarEvolution::computeExitLimitFromCond(const Loop *L,
6072 bool AllowPredicates) {
6073 // Check if the controlling expression for this loop is an And or Or.
6074 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
6075 if (BO->getOpcode() == Instruction::And) {
6076 // Recurse on the operands of the and.
6077 bool EitherMayExit = L->contains(TBB);
6078 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
6079 ControlsExit && !EitherMayExit,
6081 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
6082 ControlsExit && !EitherMayExit,
6084 const SCEV *BECount = getCouldNotCompute();
6085 const SCEV *MaxBECount = getCouldNotCompute();
6086 if (EitherMayExit) {
6087 // Both conditions must be true for the loop to continue executing.
6088 // Choose the less conservative count.
6089 if (EL0.ExactNotTaken == getCouldNotCompute() ||
6090 EL1.ExactNotTaken == getCouldNotCompute())
6091 BECount = getCouldNotCompute();
6094 getUMinFromMismatchedTypes(EL0.ExactNotTaken, EL1.ExactNotTaken);
6095 if (EL0.MaxNotTaken == getCouldNotCompute())
6096 MaxBECount = EL1.MaxNotTaken;
6097 else if (EL1.MaxNotTaken == getCouldNotCompute())
6098 MaxBECount = EL0.MaxNotTaken;
6101 getUMinFromMismatchedTypes(EL0.MaxNotTaken, EL1.MaxNotTaken);
6103 // Both conditions must be true at the same time for the loop to exit.
6104 // For now, be conservative.
6105 assert(L->contains(FBB) && "Loop block has no successor in loop!");
6106 if (EL0.MaxNotTaken == EL1.MaxNotTaken)
6107 MaxBECount = EL0.MaxNotTaken;
6108 if (EL0.ExactNotTaken == EL1.ExactNotTaken)
6109 BECount = EL0.ExactNotTaken;
6112 // There are cases (e.g. PR26207) where computeExitLimitFromCond is able
6113 // to be more aggressive when computing BECount than when computing
6114 // MaxBECount. In these cases it is possible for EL0.ExactNotTaken and
6115 // EL1.ExactNotTaken to match, but for EL0.MaxNotTaken and EL1.MaxNotTaken
6117 if (isa<SCEVCouldNotCompute>(MaxBECount) &&
6118 !isa<SCEVCouldNotCompute>(BECount))
6119 MaxBECount = BECount;
6121 return ExitLimit(BECount, MaxBECount, false,
6122 {&EL0.Predicates, &EL1.Predicates});
6124 if (BO->getOpcode() == Instruction::Or) {
6125 // Recurse on the operands of the or.
6126 bool EitherMayExit = L->contains(FBB);
6127 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
6128 ControlsExit && !EitherMayExit,
6130 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
6131 ControlsExit && !EitherMayExit,
6133 const SCEV *BECount = getCouldNotCompute();
6134 const SCEV *MaxBECount = getCouldNotCompute();
6135 if (EitherMayExit) {
6136 // Both conditions must be false for the loop to continue executing.
6137 // Choose the less conservative count.
6138 if (EL0.ExactNotTaken == getCouldNotCompute() ||
6139 EL1.ExactNotTaken == getCouldNotCompute())
6140 BECount = getCouldNotCompute();
6143 getUMinFromMismatchedTypes(EL0.ExactNotTaken, EL1.ExactNotTaken);
6144 if (EL0.MaxNotTaken == getCouldNotCompute())
6145 MaxBECount = EL1.MaxNotTaken;
6146 else if (EL1.MaxNotTaken == getCouldNotCompute())
6147 MaxBECount = EL0.MaxNotTaken;
6150 getUMinFromMismatchedTypes(EL0.MaxNotTaken, EL1.MaxNotTaken);
6152 // Both conditions must be false at the same time for the loop to exit.
6153 // For now, be conservative.
6154 assert(L->contains(TBB) && "Loop block has no successor in loop!");
6155 if (EL0.MaxNotTaken == EL1.MaxNotTaken)
6156 MaxBECount = EL0.MaxNotTaken;
6157 if (EL0.ExactNotTaken == EL1.ExactNotTaken)
6158 BECount = EL0.ExactNotTaken;
6161 return ExitLimit(BECount, MaxBECount, false,
6162 {&EL0.Predicates, &EL1.Predicates});
6166 // With an icmp, it may be feasible to compute an exact backedge-taken count.
6167 // Proceed to the next level to examine the icmp.
6168 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond)) {
6170 computeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
6171 if (EL.hasFullInfo() || !AllowPredicates)
6174 // Try again, but use SCEV predicates this time.
6175 return computeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit,
6176 /*AllowPredicates=*/true);
6179 // Check for a constant condition. These are normally stripped out by
6180 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
6181 // preserve the CFG and is temporarily leaving constant conditions
6183 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
6184 if (L->contains(FBB) == !CI->getZExtValue())
6185 // The backedge is always taken.
6186 return getCouldNotCompute();
6188 // The backedge is never taken.
6189 return getZero(CI->getType());
6192 // If it's not an integer or pointer comparison then compute it the hard way.
6193 return computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
6196 ScalarEvolution::ExitLimit
6197 ScalarEvolution::computeExitLimitFromICmp(const Loop *L,
6202 bool AllowPredicates) {
6204 // If the condition was exit on true, convert the condition to exit on false
6205 ICmpInst::Predicate Cond;
6206 if (!L->contains(FBB))
6207 Cond = ExitCond->getPredicate();
6209 Cond = ExitCond->getInversePredicate();
6211 // Handle common loops like: for (X = "string"; *X; ++X)
6212 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
6213 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
6215 computeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
6216 if (ItCnt.hasAnyInfo())
6220 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
6221 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
6223 // Try to evaluate any dependencies out of the loop.
6224 LHS = getSCEVAtScope(LHS, L);
6225 RHS = getSCEVAtScope(RHS, L);
6227 // At this point, we would like to compute how many iterations of the
6228 // loop the predicate will return true for these inputs.
6229 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
6230 // If there is a loop-invariant, force it into the RHS.
6231 std::swap(LHS, RHS);
6232 Cond = ICmpInst::getSwappedPredicate(Cond);
6235 // Simplify the operands before analyzing them.
6236 (void)SimplifyICmpOperands(Cond, LHS, RHS);
6238 // If we have a comparison of a chrec against a constant, try to use value
6239 // ranges to answer this query.
6240 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
6241 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
6242 if (AddRec->getLoop() == L) {
6243 // Form the constant range.
6244 ConstantRange CompRange =
6245 ConstantRange::makeExactICmpRegion(Cond, RHSC->getAPInt());
6247 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
6248 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
6252 case ICmpInst::ICMP_NE: { // while (X != Y)
6253 // Convert to: while (X-Y != 0)
6254 ExitLimit EL = howFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit,
6256 if (EL.hasAnyInfo()) return EL;
6259 case ICmpInst::ICMP_EQ: { // while (X == Y)
6260 // Convert to: while (X-Y == 0)
6261 ExitLimit EL = howFarToNonZero(getMinusSCEV(LHS, RHS), L);
6262 if (EL.hasAnyInfo()) return EL;
6265 case ICmpInst::ICMP_SLT:
6266 case ICmpInst::ICMP_ULT: { // while (X < Y)
6267 bool IsSigned = Cond == ICmpInst::ICMP_SLT;
6268 ExitLimit EL = howManyLessThans(LHS, RHS, L, IsSigned, ControlsExit,
6270 if (EL.hasAnyInfo()) return EL;
6273 case ICmpInst::ICMP_SGT:
6274 case ICmpInst::ICMP_UGT: { // while (X > Y)
6275 bool IsSigned = Cond == ICmpInst::ICMP_SGT;
6277 howManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit,
6279 if (EL.hasAnyInfo()) return EL;
6286 auto *ExhaustiveCount =
6287 computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
6289 if (!isa<SCEVCouldNotCompute>(ExhaustiveCount))
6290 return ExhaustiveCount;
6292 return computeShiftCompareExitLimit(ExitCond->getOperand(0),
6293 ExitCond->getOperand(1), L, Cond);
6296 ScalarEvolution::ExitLimit
6297 ScalarEvolution::computeExitLimitFromSingleExitSwitch(const Loop *L,
6299 BasicBlock *ExitingBlock,
6300 bool ControlsExit) {
6301 assert(!L->contains(ExitingBlock) && "Not an exiting block!");
6303 // Give up if the exit is the default dest of a switch.
6304 if (Switch->getDefaultDest() == ExitingBlock)
6305 return getCouldNotCompute();
6307 assert(L->contains(Switch->getDefaultDest()) &&
6308 "Default case must not exit the loop!");
6309 const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L);
6310 const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock));
6312 // while (X != Y) --> while (X-Y != 0)
6313 ExitLimit EL = howFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
6314 if (EL.hasAnyInfo())
6317 return getCouldNotCompute();
6320 static ConstantInt *
6321 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
6322 ScalarEvolution &SE) {
6323 const SCEV *InVal = SE.getConstant(C);
6324 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
6325 assert(isa<SCEVConstant>(Val) &&
6326 "Evaluation of SCEV at constant didn't fold correctly?");
6327 return cast<SCEVConstant>(Val)->getValue();
6330 /// Given an exit condition of 'icmp op load X, cst', try to see if we can
6331 /// compute the backedge execution count.
6332 ScalarEvolution::ExitLimit
6333 ScalarEvolution::computeLoadConstantCompareExitLimit(
6337 ICmpInst::Predicate predicate) {
6339 if (LI->isVolatile()) return getCouldNotCompute();
6341 // Check to see if the loaded pointer is a getelementptr of a global.
6342 // TODO: Use SCEV instead of manually grubbing with GEPs.
6343 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
6344 if (!GEP) return getCouldNotCompute();
6346 // Make sure that it is really a constant global we are gepping, with an
6347 // initializer, and make sure the first IDX is really 0.
6348 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
6349 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
6350 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
6351 !cast<Constant>(GEP->getOperand(1))->isNullValue())
6352 return getCouldNotCompute();
6354 // Okay, we allow one non-constant index into the GEP instruction.
6355 Value *VarIdx = nullptr;
6356 std::vector<Constant*> Indexes;
6357 unsigned VarIdxNum = 0;
6358 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
6359 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
6360 Indexes.push_back(CI);
6361 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
6362 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
6363 VarIdx = GEP->getOperand(i);
6365 Indexes.push_back(nullptr);
6368 // Loop-invariant loads may be a byproduct of loop optimization. Skip them.
6370 return getCouldNotCompute();
6372 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
6373 // Check to see if X is a loop variant variable value now.
6374 const SCEV *Idx = getSCEV(VarIdx);
6375 Idx = getSCEVAtScope(Idx, L);
6377 // We can only recognize very limited forms of loop index expressions, in
6378 // particular, only affine AddRec's like {C1,+,C2}.
6379 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
6380 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
6381 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
6382 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
6383 return getCouldNotCompute();
6385 unsigned MaxSteps = MaxBruteForceIterations;
6386 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
6387 ConstantInt *ItCst = ConstantInt::get(
6388 cast<IntegerType>(IdxExpr->getType()), IterationNum);
6389 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
6391 // Form the GEP offset.
6392 Indexes[VarIdxNum] = Val;
6394 Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
6396 if (!Result) break; // Cannot compute!
6398 // Evaluate the condition for this iteration.
6399 Result = ConstantExpr::getICmp(predicate, Result, RHS);
6400 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
6401 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
6402 ++NumArrayLenItCounts;
6403 return getConstant(ItCst); // Found terminating iteration!
6406 return getCouldNotCompute();
6409 ScalarEvolution::ExitLimit ScalarEvolution::computeShiftCompareExitLimit(
6410 Value *LHS, Value *RHSV, const Loop *L, ICmpInst::Predicate Pred) {
6411 ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV);
6413 return getCouldNotCompute();
6415 const BasicBlock *Latch = L->getLoopLatch();
6417 return getCouldNotCompute();
6419 const BasicBlock *Predecessor = L->getLoopPredecessor();
6421 return getCouldNotCompute();
6423 // Return true if V is of the form "LHS `shift_op` <positive constant>".
6424 // Return LHS in OutLHS and shift_opt in OutOpCode.
6425 auto MatchPositiveShift =
6426 [](Value *V, Value *&OutLHS, Instruction::BinaryOps &OutOpCode) {
6428 using namespace PatternMatch;
6430 ConstantInt *ShiftAmt;
6431 if (match(V, m_LShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
6432 OutOpCode = Instruction::LShr;
6433 else if (match(V, m_AShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
6434 OutOpCode = Instruction::AShr;
6435 else if (match(V, m_Shl(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
6436 OutOpCode = Instruction::Shl;
6440 return ShiftAmt->getValue().isStrictlyPositive();
6443 // Recognize a "shift recurrence" either of the form %iv or of %iv.shifted in
6446 // %iv = phi i32 [ %iv.shifted, %loop ], [ %val, %preheader ]
6447 // %iv.shifted = lshr i32 %iv, <positive constant>
6449 // Return true on a successful match. Return the corresponding PHI node (%iv
6450 // above) in PNOut and the opcode of the shift operation in OpCodeOut.
6451 auto MatchShiftRecurrence =
6452 [&](Value *V, PHINode *&PNOut, Instruction::BinaryOps &OpCodeOut) {
6453 Optional<Instruction::BinaryOps> PostShiftOpCode;
6456 Instruction::BinaryOps OpC;
6459 // If we encounter a shift instruction, "peel off" the shift operation,
6460 // and remember that we did so. Later when we inspect %iv's backedge
6461 // value, we will make sure that the backedge value uses the same
6464 // Note: the peeled shift operation does not have to be the same
6465 // instruction as the one feeding into the PHI's backedge value. We only
6466 // really care about it being the same *kind* of shift instruction --
6467 // that's all that is required for our later inferences to hold.
6468 if (MatchPositiveShift(LHS, V, OpC)) {
6469 PostShiftOpCode = OpC;
6474 PNOut = dyn_cast<PHINode>(LHS);
6475 if (!PNOut || PNOut->getParent() != L->getHeader())
6478 Value *BEValue = PNOut->getIncomingValueForBlock(Latch);
6482 // The backedge value for the PHI node must be a shift by a positive
6484 MatchPositiveShift(BEValue, OpLHS, OpCodeOut) &&
6486 // of the PHI node itself
6489 // and the kind of shift should be match the kind of shift we peeled
6491 (!PostShiftOpCode.hasValue() || *PostShiftOpCode == OpCodeOut);
6495 Instruction::BinaryOps OpCode;
6496 if (!MatchShiftRecurrence(LHS, PN, OpCode))
6497 return getCouldNotCompute();
6499 const DataLayout &DL = getDataLayout();
6501 // The key rationale for this optimization is that for some kinds of shift
6502 // recurrences, the value of the recurrence "stabilizes" to either 0 or -1
6503 // within a finite number of iterations. If the condition guarding the
6504 // backedge (in the sense that the backedge is taken if the condition is true)
6505 // is false for the value the shift recurrence stabilizes to, then we know
6506 // that the backedge is taken only a finite number of times.
6508 ConstantInt *StableValue = nullptr;
6511 llvm_unreachable("Impossible case!");
6513 case Instruction::AShr: {
6514 // {K,ashr,<positive-constant>} stabilizes to signum(K) in at most
6515 // bitwidth(K) iterations.
6516 Value *FirstValue = PN->getIncomingValueForBlock(Predecessor);
6517 bool KnownZero, KnownOne;
6518 ComputeSignBit(FirstValue, KnownZero, KnownOne, DL, 0, nullptr,
6519 Predecessor->getTerminator(), &DT);
6520 auto *Ty = cast<IntegerType>(RHS->getType());
6522 StableValue = ConstantInt::get(Ty, 0);
6524 StableValue = ConstantInt::get(Ty, -1, true);
6526 return getCouldNotCompute();
6530 case Instruction::LShr:
6531 case Instruction::Shl:
6532 // Both {K,lshr,<positive-constant>} and {K,shl,<positive-constant>}
6533 // stabilize to 0 in at most bitwidth(K) iterations.
6534 StableValue = ConstantInt::get(cast<IntegerType>(RHS->getType()), 0);
6539 ConstantFoldCompareInstOperands(Pred, StableValue, RHS, DL, &TLI);
6540 assert(Result->getType()->isIntegerTy(1) &&
6541 "Otherwise cannot be an operand to a branch instruction");
6543 if (Result->isZeroValue()) {
6544 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
6545 const SCEV *UpperBound =
6546 getConstant(getEffectiveSCEVType(RHS->getType()), BitWidth);
6547 return ExitLimit(getCouldNotCompute(), UpperBound, false);
6550 return getCouldNotCompute();
6553 /// Return true if we can constant fold an instruction of the specified type,
6554 /// assuming that all operands were constants.
6555 static bool CanConstantFold(const Instruction *I) {
6556 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
6557 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
6561 if (const CallInst *CI = dyn_cast<CallInst>(I))
6562 if (const Function *F = CI->getCalledFunction())
6563 return canConstantFoldCallTo(F);
6567 /// Determine whether this instruction can constant evolve within this loop
6568 /// assuming its operands can all constant evolve.
6569 static bool canConstantEvolve(Instruction *I, const Loop *L) {
6570 // An instruction outside of the loop can't be derived from a loop PHI.
6571 if (!L->contains(I)) return false;
6573 if (isa<PHINode>(I)) {
6574 // We don't currently keep track of the control flow needed to evaluate
6575 // PHIs, so we cannot handle PHIs inside of loops.
6576 return L->getHeader() == I->getParent();
6579 // If we won't be able to constant fold this expression even if the operands
6580 // are constants, bail early.
6581 return CanConstantFold(I);
6584 /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
6585 /// recursing through each instruction operand until reaching a loop header phi.
6587 getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
6588 DenseMap<Instruction *, PHINode *> &PHIMap,
6590 if (Depth > MaxConstantEvolvingDepth)
6593 // Otherwise, we can evaluate this instruction if all of its operands are
6594 // constant or derived from a PHI node themselves.
6595 PHINode *PHI = nullptr;
6596 for (Value *Op : UseInst->operands()) {
6597 if (isa<Constant>(Op)) continue;
6599 Instruction *OpInst = dyn_cast<Instruction>(Op);
6600 if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
6602 PHINode *P = dyn_cast<PHINode>(OpInst);
6604 // If this operand is already visited, reuse the prior result.
6605 // We may have P != PHI if this is the deepest point at which the
6606 // inconsistent paths meet.
6607 P = PHIMap.lookup(OpInst);
6609 // Recurse and memoize the results, whether a phi is found or not.
6610 // This recursive call invalidates pointers into PHIMap.
6611 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap, Depth + 1);
6615 return nullptr; // Not evolving from PHI
6616 if (PHI && PHI != P)
6617 return nullptr; // Evolving from multiple different PHIs.
6620 // This is a expression evolving from a constant PHI!
6624 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
6625 /// in the loop that V is derived from. We allow arbitrary operations along the
6626 /// way, but the operands of an operation must either be constants or a value
6627 /// derived from a constant PHI. If this expression does not fit with these
6628 /// constraints, return null.
6629 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
6630 Instruction *I = dyn_cast<Instruction>(V);
6631 if (!I || !canConstantEvolve(I, L)) return nullptr;
6633 if (PHINode *PN = dyn_cast<PHINode>(I))
6636 // Record non-constant instructions contained by the loop.
6637 DenseMap<Instruction *, PHINode *> PHIMap;
6638 return getConstantEvolvingPHIOperands(I, L, PHIMap, 0);
6641 /// EvaluateExpression - Given an expression that passes the
6642 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
6643 /// in the loop has the value PHIVal. If we can't fold this expression for some
6644 /// reason, return null.
6645 static Constant *EvaluateExpression(Value *V, const Loop *L,
6646 DenseMap<Instruction *, Constant *> &Vals,
6647 const DataLayout &DL,
6648 const TargetLibraryInfo *TLI) {
6649 // Convenient constant check, but redundant for recursive calls.
6650 if (Constant *C = dyn_cast<Constant>(V)) return C;
6651 Instruction *I = dyn_cast<Instruction>(V);
6652 if (!I) return nullptr;
6654 if (Constant *C = Vals.lookup(I)) return C;
6656 // An instruction inside the loop depends on a value outside the loop that we
6657 // weren't given a mapping for, or a value such as a call inside the loop.
6658 if (!canConstantEvolve(I, L)) return nullptr;
6660 // An unmapped PHI can be due to a branch or another loop inside this loop,
6661 // or due to this not being the initial iteration through a loop where we
6662 // couldn't compute the evolution of this particular PHI last time.
6663 if (isa<PHINode>(I)) return nullptr;
6665 std::vector<Constant*> Operands(I->getNumOperands());
6667 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
6668 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
6670 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
6671 if (!Operands[i]) return nullptr;
6674 Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
6676 if (!C) return nullptr;
6680 if (CmpInst *CI = dyn_cast<CmpInst>(I))
6681 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
6682 Operands[1], DL, TLI);
6683 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
6684 if (!LI->isVolatile())
6685 return ConstantFoldLoadFromConstPtr(Operands[0], LI->getType(), DL);
6687 return ConstantFoldInstOperands(I, Operands, DL, TLI);
6691 // If every incoming value to PN except the one for BB is a specific Constant,
6692 // return that, else return nullptr.
6693 static Constant *getOtherIncomingValue(PHINode *PN, BasicBlock *BB) {
6694 Constant *IncomingVal = nullptr;
6696 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
6697 if (PN->getIncomingBlock(i) == BB)
6700 auto *CurrentVal = dyn_cast<Constant>(PN->getIncomingValue(i));
6704 if (IncomingVal != CurrentVal) {
6707 IncomingVal = CurrentVal;
6714 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
6715 /// in the header of its containing loop, we know the loop executes a
6716 /// constant number of times, and the PHI node is just a recurrence
6717 /// involving constants, fold it.
6719 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
6722 auto I = ConstantEvolutionLoopExitValue.find(PN);
6723 if (I != ConstantEvolutionLoopExitValue.end())
6726 if (BEs.ugt(MaxBruteForceIterations))
6727 return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
6729 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
6731 DenseMap<Instruction *, Constant *> CurrentIterVals;
6732 BasicBlock *Header = L->getHeader();
6733 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
6735 BasicBlock *Latch = L->getLoopLatch();
6739 for (auto &I : *Header) {
6740 PHINode *PHI = dyn_cast<PHINode>(&I);
6742 auto *StartCST = getOtherIncomingValue(PHI, Latch);
6743 if (!StartCST) continue;
6744 CurrentIterVals[PHI] = StartCST;
6746 if (!CurrentIterVals.count(PN))
6747 return RetVal = nullptr;
6749 Value *BEValue = PN->getIncomingValueForBlock(Latch);
6751 // Execute the loop symbolically to determine the exit value.
6752 if (BEs.getActiveBits() >= 32)
6753 return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
6755 unsigned NumIterations = BEs.getZExtValue(); // must be in range
6756 unsigned IterationNum = 0;
6757 const DataLayout &DL = getDataLayout();
6758 for (; ; ++IterationNum) {
6759 if (IterationNum == NumIterations)
6760 return RetVal = CurrentIterVals[PN]; // Got exit value!
6762 // Compute the value of the PHIs for the next iteration.
6763 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
6764 DenseMap<Instruction *, Constant *> NextIterVals;
6766 EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6768 return nullptr; // Couldn't evaluate!
6769 NextIterVals[PN] = NextPHI;
6771 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
6773 // Also evaluate the other PHI nodes. However, we don't get to stop if we
6774 // cease to be able to evaluate one of them or if they stop evolving,
6775 // because that doesn't necessarily prevent us from computing PN.
6776 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
6777 for (const auto &I : CurrentIterVals) {
6778 PHINode *PHI = dyn_cast<PHINode>(I.first);
6779 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
6780 PHIsToCompute.emplace_back(PHI, I.second);
6782 // We use two distinct loops because EvaluateExpression may invalidate any
6783 // iterators into CurrentIterVals.
6784 for (const auto &I : PHIsToCompute) {
6785 PHINode *PHI = I.first;
6786 Constant *&NextPHI = NextIterVals[PHI];
6787 if (!NextPHI) { // Not already computed.
6788 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
6789 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6791 if (NextPHI != I.second)
6792 StoppedEvolving = false;
6795 // If all entries in CurrentIterVals == NextIterVals then we can stop
6796 // iterating, the loop can't continue to change.
6797 if (StoppedEvolving)
6798 return RetVal = CurrentIterVals[PN];
6800 CurrentIterVals.swap(NextIterVals);
6804 const SCEV *ScalarEvolution::computeExitCountExhaustively(const Loop *L,
6807 PHINode *PN = getConstantEvolvingPHI(Cond, L);
6808 if (!PN) return getCouldNotCompute();
6810 // If the loop is canonicalized, the PHI will have exactly two entries.
6811 // That's the only form we support here.
6812 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
6814 DenseMap<Instruction *, Constant *> CurrentIterVals;
6815 BasicBlock *Header = L->getHeader();
6816 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
6818 BasicBlock *Latch = L->getLoopLatch();
6819 assert(Latch && "Should follow from NumIncomingValues == 2!");
6821 for (auto &I : *Header) {
6822 PHINode *PHI = dyn_cast<PHINode>(&I);
6825 auto *StartCST = getOtherIncomingValue(PHI, Latch);
6826 if (!StartCST) continue;
6827 CurrentIterVals[PHI] = StartCST;
6829 if (!CurrentIterVals.count(PN))
6830 return getCouldNotCompute();
6832 // Okay, we find a PHI node that defines the trip count of this loop. Execute
6833 // the loop symbolically to determine when the condition gets a value of
6835 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
6836 const DataLayout &DL = getDataLayout();
6837 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
6838 auto *CondVal = dyn_cast_or_null<ConstantInt>(
6839 EvaluateExpression(Cond, L, CurrentIterVals, DL, &TLI));
6841 // Couldn't symbolically evaluate.
6842 if (!CondVal) return getCouldNotCompute();
6844 if (CondVal->getValue() == uint64_t(ExitWhen)) {
6845 ++NumBruteForceTripCountsComputed;
6846 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
6849 // Update all the PHI nodes for the next iteration.
6850 DenseMap<Instruction *, Constant *> NextIterVals;
6852 // Create a list of which PHIs we need to compute. We want to do this before
6853 // calling EvaluateExpression on them because that may invalidate iterators
6854 // into CurrentIterVals.
6855 SmallVector<PHINode *, 8> PHIsToCompute;
6856 for (const auto &I : CurrentIterVals) {
6857 PHINode *PHI = dyn_cast<PHINode>(I.first);
6858 if (!PHI || PHI->getParent() != Header) continue;
6859 PHIsToCompute.push_back(PHI);
6861 for (PHINode *PHI : PHIsToCompute) {
6862 Constant *&NextPHI = NextIterVals[PHI];
6863 if (NextPHI) continue; // Already computed!
6865 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
6866 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6868 CurrentIterVals.swap(NextIterVals);
6871 // Too many iterations were needed to evaluate.
6872 return getCouldNotCompute();
6875 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
6876 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values =
6878 // Check to see if we've folded this expression at this loop before.
6879 for (auto &LS : Values)
6881 return LS.second ? LS.second : V;
6883 Values.emplace_back(L, nullptr);
6885 // Otherwise compute it.
6886 const SCEV *C = computeSCEVAtScope(V, L);
6887 for (auto &LS : reverse(ValuesAtScopes[V]))
6888 if (LS.first == L) {
6895 /// This builds up a Constant using the ConstantExpr interface. That way, we
6896 /// will return Constants for objects which aren't represented by a
6897 /// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
6898 /// Returns NULL if the SCEV isn't representable as a Constant.
6899 static Constant *BuildConstantFromSCEV(const SCEV *V) {
6900 switch (static_cast<SCEVTypes>(V->getSCEVType())) {
6901 case scCouldNotCompute:
6905 return cast<SCEVConstant>(V)->getValue();
6907 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
6908 case scSignExtend: {
6909 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
6910 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
6911 return ConstantExpr::getSExt(CastOp, SS->getType());
6914 case scZeroExtend: {
6915 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
6916 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
6917 return ConstantExpr::getZExt(CastOp, SZ->getType());
6921 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
6922 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
6923 return ConstantExpr::getTrunc(CastOp, ST->getType());
6927 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
6928 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
6929 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6930 unsigned AS = PTy->getAddressSpace();
6931 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
6932 C = ConstantExpr::getBitCast(C, DestPtrTy);
6934 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
6935 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
6936 if (!C2) return nullptr;
6939 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
6940 unsigned AS = C2->getType()->getPointerAddressSpace();
6942 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
6943 // The offsets have been converted to bytes. We can add bytes to an
6944 // i8* by GEP with the byte count in the first index.
6945 C = ConstantExpr::getBitCast(C, DestPtrTy);
6948 // Don't bother trying to sum two pointers. We probably can't
6949 // statically compute a load that results from it anyway.
6950 if (C2->getType()->isPointerTy())
6953 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6954 if (PTy->getElementType()->isStructTy())
6955 C2 = ConstantExpr::getIntegerCast(
6956 C2, Type::getInt32Ty(C->getContext()), true);
6957 C = ConstantExpr::getGetElementPtr(PTy->getElementType(), C, C2);
6959 C = ConstantExpr::getAdd(C, C2);
6966 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
6967 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
6968 // Don't bother with pointers at all.
6969 if (C->getType()->isPointerTy()) return nullptr;
6970 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
6971 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
6972 if (!C2 || C2->getType()->isPointerTy()) return nullptr;
6973 C = ConstantExpr::getMul(C, C2);
6980 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
6981 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
6982 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
6983 if (LHS->getType() == RHS->getType())
6984 return ConstantExpr::getUDiv(LHS, RHS);
6989 break; // TODO: smax, umax.
6994 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
6995 if (isa<SCEVConstant>(V)) return V;
6997 // If this instruction is evolved from a constant-evolving PHI, compute the
6998 // exit value from the loop without using SCEVs.
6999 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
7000 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
7001 const Loop *LI = this->LI[I->getParent()];
7002 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
7003 if (PHINode *PN = dyn_cast<PHINode>(I))
7004 if (PN->getParent() == LI->getHeader()) {
7005 // Okay, there is no closed form solution for the PHI node. Check
7006 // to see if the loop that contains it has a known backedge-taken
7007 // count. If so, we may be able to force computation of the exit
7009 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
7010 if (const SCEVConstant *BTCC =
7011 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
7012 // Okay, we know how many times the containing loop executes. If
7013 // this is a constant evolving PHI node, get the final value at
7014 // the specified iteration number.
7016 getConstantEvolutionLoopExitValue(PN, BTCC->getAPInt(), LI);
7017 if (RV) return getSCEV(RV);
7021 // Okay, this is an expression that we cannot symbolically evaluate
7022 // into a SCEV. Check to see if it's possible to symbolically evaluate
7023 // the arguments into constants, and if so, try to constant propagate the
7024 // result. This is particularly useful for computing loop exit values.
7025 if (CanConstantFold(I)) {
7026 SmallVector<Constant *, 4> Operands;
7027 bool MadeImprovement = false;
7028 for (Value *Op : I->operands()) {
7029 if (Constant *C = dyn_cast<Constant>(Op)) {
7030 Operands.push_back(C);
7034 // If any of the operands is non-constant and if they are
7035 // non-integer and non-pointer, don't even try to analyze them
7036 // with scev techniques.
7037 if (!isSCEVable(Op->getType()))
7040 const SCEV *OrigV = getSCEV(Op);
7041 const SCEV *OpV = getSCEVAtScope(OrigV, L);
7042 MadeImprovement |= OrigV != OpV;
7044 Constant *C = BuildConstantFromSCEV(OpV);
7046 if (C->getType() != Op->getType())
7047 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
7051 Operands.push_back(C);
7054 // Check to see if getSCEVAtScope actually made an improvement.
7055 if (MadeImprovement) {
7056 Constant *C = nullptr;
7057 const DataLayout &DL = getDataLayout();
7058 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
7059 C = ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
7060 Operands[1], DL, &TLI);
7061 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
7062 if (!LI->isVolatile())
7063 C = ConstantFoldLoadFromConstPtr(Operands[0], LI->getType(), DL);
7065 C = ConstantFoldInstOperands(I, Operands, DL, &TLI);
7072 // This is some other type of SCEVUnknown, just return it.
7076 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
7077 // Avoid performing the look-up in the common case where the specified
7078 // expression has no loop-variant portions.
7079 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
7080 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
7081 if (OpAtScope != Comm->getOperand(i)) {
7082 // Okay, at least one of these operands is loop variant but might be
7083 // foldable. Build a new instance of the folded commutative expression.
7084 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
7085 Comm->op_begin()+i);
7086 NewOps.push_back(OpAtScope);
7088 for (++i; i != e; ++i) {
7089 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
7090 NewOps.push_back(OpAtScope);
7092 if (isa<SCEVAddExpr>(Comm))
7093 return getAddExpr(NewOps);
7094 if (isa<SCEVMulExpr>(Comm))
7095 return getMulExpr(NewOps);
7096 if (isa<SCEVSMaxExpr>(Comm))
7097 return getSMaxExpr(NewOps);
7098 if (isa<SCEVUMaxExpr>(Comm))
7099 return getUMaxExpr(NewOps);
7100 llvm_unreachable("Unknown commutative SCEV type!");
7103 // If we got here, all operands are loop invariant.
7107 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
7108 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
7109 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
7110 if (LHS == Div->getLHS() && RHS == Div->getRHS())
7111 return Div; // must be loop invariant
7112 return getUDivExpr(LHS, RHS);
7115 // If this is a loop recurrence for a loop that does not contain L, then we
7116 // are dealing with the final value computed by the loop.
7117 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
7118 // First, attempt to evaluate each operand.
7119 // Avoid performing the look-up in the common case where the specified
7120 // expression has no loop-variant portions.
7121 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
7122 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
7123 if (OpAtScope == AddRec->getOperand(i))
7126 // Okay, at least one of these operands is loop variant but might be
7127 // foldable. Build a new instance of the folded commutative expression.
7128 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
7129 AddRec->op_begin()+i);
7130 NewOps.push_back(OpAtScope);
7131 for (++i; i != e; ++i)
7132 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
7134 const SCEV *FoldedRec =
7135 getAddRecExpr(NewOps, AddRec->getLoop(),
7136 AddRec->getNoWrapFlags(SCEV::FlagNW));
7137 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
7138 // The addrec may be folded to a nonrecurrence, for example, if the
7139 // induction variable is multiplied by zero after constant folding. Go
7140 // ahead and return the folded value.
7146 // If the scope is outside the addrec's loop, evaluate it by using the
7147 // loop exit value of the addrec.
7148 if (!AddRec->getLoop()->contains(L)) {
7149 // To evaluate this recurrence, we need to know how many times the AddRec
7150 // loop iterates. Compute this now.
7151 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
7152 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
7154 // Then, evaluate the AddRec.
7155 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
7161 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
7162 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
7163 if (Op == Cast->getOperand())
7164 return Cast; // must be loop invariant
7165 return getZeroExtendExpr(Op, Cast->getType());
7168 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
7169 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
7170 if (Op == Cast->getOperand())
7171 return Cast; // must be loop invariant
7172 return getSignExtendExpr(Op, Cast->getType());
7175 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
7176 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
7177 if (Op == Cast->getOperand())
7178 return Cast; // must be loop invariant
7179 return getTruncateExpr(Op, Cast->getType());
7182 llvm_unreachable("Unknown SCEV type!");
7185 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
7186 return getSCEVAtScope(getSCEV(V), L);
7189 /// Finds the minimum unsigned root of the following equation:
7191 /// A * X = B (mod N)
7193 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
7194 /// A and B isn't important.
7196 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
7197 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const SCEV *B,
7198 ScalarEvolution &SE) {
7199 uint32_t BW = A.getBitWidth();
7200 assert(BW == SE.getTypeSizeInBits(B->getType()));
7201 assert(A != 0 && "A must be non-zero.");
7205 // The gcd of A and N may have only one prime factor: 2. The number of
7206 // trailing zeros in A is its multiplicity
7207 uint32_t Mult2 = A.countTrailingZeros();
7210 // 2. Check if B is divisible by D.
7212 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
7213 // is not less than multiplicity of this prime factor for D.
7214 if (SE.GetMinTrailingZeros(B) < Mult2)
7215 return SE.getCouldNotCompute();
7217 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
7220 // If D == 1, (N / D) == N == 2^BW, so we need one extra bit to represent
7221 // (N / D) in general. The inverse itself always fits into BW bits, though,
7222 // so we immediately truncate it.
7223 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
7224 APInt Mod(BW + 1, 0);
7225 Mod.setBit(BW - Mult2); // Mod = N / D
7226 APInt I = AD.multiplicativeInverse(Mod).trunc(BW);
7228 // 4. Compute the minimum unsigned root of the equation:
7229 // I * (B / D) mod (N / D)
7230 // To simplify the computation, we factor out the divide by D:
7231 // (I * B mod N) / D
7232 const SCEV *D = SE.getConstant(APInt::getOneBitSet(BW, Mult2));
7233 return SE.getUDivExactExpr(SE.getMulExpr(B, SE.getConstant(I)), D);
7236 /// Find the roots of the quadratic equation for the given quadratic chrec
7237 /// {L,+,M,+,N}. This returns either the two roots (which might be the same) or
7238 /// two SCEVCouldNotCompute objects.
7240 static Optional<std::pair<const SCEVConstant *,const SCEVConstant *>>
7241 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
7242 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
7243 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
7244 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
7245 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
7247 // We currently can only solve this if the coefficients are constants.
7248 if (!LC || !MC || !NC)
7251 uint32_t BitWidth = LC->getAPInt().getBitWidth();
7252 const APInt &L = LC->getAPInt();
7253 const APInt &M = MC->getAPInt();
7254 const APInt &N = NC->getAPInt();
7255 APInt Two(BitWidth, 2);
7256 APInt Four(BitWidth, 4);
7259 using namespace APIntOps;
7261 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
7262 // The B coefficient is M-N/2
7266 // The A coefficient is N/2
7267 APInt A(N.sdiv(Two));
7269 // Compute the B^2-4ac term.
7272 SqrtTerm -= Four * (A * C);
7274 if (SqrtTerm.isNegative()) {
7275 // The loop is provably infinite.
7279 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
7280 // integer value or else APInt::sqrt() will assert.
7281 APInt SqrtVal(SqrtTerm.sqrt());
7283 // Compute the two solutions for the quadratic formula.
7284 // The divisions must be performed as signed divisions.
7287 if (TwoA.isMinValue())
7290 LLVMContext &Context = SE.getContext();
7292 ConstantInt *Solution1 =
7293 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
7294 ConstantInt *Solution2 =
7295 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
7297 return std::make_pair(cast<SCEVConstant>(SE.getConstant(Solution1)),
7298 cast<SCEVConstant>(SE.getConstant(Solution2)));
7299 } // end APIntOps namespace
7302 ScalarEvolution::ExitLimit
7303 ScalarEvolution::howFarToZero(const SCEV *V, const Loop *L, bool ControlsExit,
7304 bool AllowPredicates) {
7306 // This is only used for loops with a "x != y" exit test. The exit condition
7307 // is now expressed as a single expression, V = x-y. So the exit test is
7308 // effectively V != 0. We know and take advantage of the fact that this
7309 // expression only being used in a comparison by zero context.
7311 SmallPtrSet<const SCEVPredicate *, 4> Predicates;
7312 // If the value is a constant
7313 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
7314 // If the value is already zero, the branch will execute zero times.
7315 if (C->getValue()->isZero()) return C;
7316 return getCouldNotCompute(); // Otherwise it will loop infinitely.
7319 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
7320 if (!AddRec && AllowPredicates)
7321 // Try to make this an AddRec using runtime tests, in the first X
7322 // iterations of this loop, where X is the SCEV expression found by the
7324 AddRec = convertSCEVToAddRecWithPredicates(V, L, Predicates);
7326 if (!AddRec || AddRec->getLoop() != L)
7327 return getCouldNotCompute();
7329 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
7330 // the quadratic equation to solve it.
7331 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
7332 if (auto Roots = SolveQuadraticEquation(AddRec, *this)) {
7333 const SCEVConstant *R1 = Roots->first;
7334 const SCEVConstant *R2 = Roots->second;
7335 // Pick the smallest positive root value.
7336 if (ConstantInt *CB = dyn_cast<ConstantInt>(ConstantExpr::getICmp(
7337 CmpInst::ICMP_ULT, R1->getValue(), R2->getValue()))) {
7338 if (!CB->getZExtValue())
7339 std::swap(R1, R2); // R1 is the minimum root now.
7341 // We can only use this value if the chrec ends up with an exact zero
7342 // value at this index. When solving for "X*X != 5", for example, we
7343 // should not accept a root of 2.
7344 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
7346 // We found a quadratic root!
7347 return ExitLimit(R1, R1, false, Predicates);
7350 return getCouldNotCompute();
7353 // Otherwise we can only handle this if it is affine.
7354 if (!AddRec->isAffine())
7355 return getCouldNotCompute();
7357 // If this is an affine expression, the execution count of this branch is
7358 // the minimum unsigned root of the following equation:
7360 // Start + Step*N = 0 (mod 2^BW)
7364 // Step*N = -Start (mod 2^BW)
7366 // where BW is the common bit width of Start and Step.
7368 // Get the initial value for the loop.
7369 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
7370 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
7372 // For now we handle only constant steps.
7374 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
7375 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
7376 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
7377 // We have not yet seen any such cases.
7378 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
7379 if (!StepC || StepC->getValue()->equalsInt(0))
7380 return getCouldNotCompute();
7382 // For positive steps (counting up until unsigned overflow):
7383 // N = -Start/Step (as unsigned)
7384 // For negative steps (counting down to zero):
7386 // First compute the unsigned distance from zero in the direction of Step.
7387 bool CountDown = StepC->getAPInt().isNegative();
7388 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
7390 // Handle unitary steps, which cannot wraparound.
7391 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
7392 // N = Distance (as unsigned)
7393 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
7394 APInt MaxBECount = getUnsignedRange(Distance).getUnsignedMax();
7396 // When a loop like "for (int i = 0; i != n; ++i) { /* body */ }" is rotated,
7397 // we end up with a loop whose backedge-taken count is n - 1. Detect this
7398 // case, and see if we can improve the bound.
7400 // Explicitly handling this here is necessary because getUnsignedRange
7401 // isn't context-sensitive; it doesn't know that we only care about the
7402 // range inside the loop.
7403 const SCEV *Zero = getZero(Distance->getType());
7404 const SCEV *One = getOne(Distance->getType());
7405 const SCEV *DistancePlusOne = getAddExpr(Distance, One);
7406 if (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_NE, DistancePlusOne, Zero)) {
7407 // If Distance + 1 doesn't overflow, we can compute the maximum distance
7408 // as "unsigned_max(Distance + 1) - 1".
7409 ConstantRange CR = getUnsignedRange(DistancePlusOne);
7410 MaxBECount = APIntOps::umin(MaxBECount, CR.getUnsignedMax() - 1);
7412 return ExitLimit(Distance, getConstant(MaxBECount), false, Predicates);
7415 // If the condition controls loop exit (the loop exits only if the expression
7416 // is true) and the addition is no-wrap we can use unsigned divide to
7417 // compute the backedge count. In this case, the step may not divide the
7418 // distance, but we don't care because if the condition is "missed" the loop
7419 // will have undefined behavior due to wrapping.
7420 if (ControlsExit && AddRec->hasNoSelfWrap() &&
7421 loopHasNoAbnormalExits(AddRec->getLoop())) {
7423 getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
7424 return ExitLimit(Exact, Exact, false, Predicates);
7427 // Solve the general equation.
7428 const SCEV *E = SolveLinEquationWithOverflow(
7429 StepC->getAPInt(), getNegativeSCEV(Start), *this);
7430 return ExitLimit(E, E, false, Predicates);
7433 ScalarEvolution::ExitLimit
7434 ScalarEvolution::howFarToNonZero(const SCEV *V, const Loop *L) {
7435 // Loops that look like: while (X == 0) are very strange indeed. We don't
7436 // handle them yet except for the trivial case. This could be expanded in the
7437 // future as needed.
7439 // If the value is a constant, check to see if it is known to be non-zero
7440 // already. If so, the backedge will execute zero times.
7441 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
7442 if (!C->getValue()->isNullValue())
7443 return getZero(C->getType());
7444 return getCouldNotCompute(); // Otherwise it will loop infinitely.
7447 // We could implement others, but I really doubt anyone writes loops like
7448 // this, and if they did, they would already be constant folded.
7449 return getCouldNotCompute();
7452 std::pair<BasicBlock *, BasicBlock *>
7453 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
7454 // If the block has a unique predecessor, then there is no path from the
7455 // predecessor to the block that does not go through the direct edge
7456 // from the predecessor to the block.
7457 if (BasicBlock *Pred = BB->getSinglePredecessor())
7460 // A loop's header is defined to be a block that dominates the loop.
7461 // If the header has a unique predecessor outside the loop, it must be
7462 // a block that has exactly one successor that can reach the loop.
7463 if (Loop *L = LI.getLoopFor(BB))
7464 return {L->getLoopPredecessor(), L->getHeader()};
7466 return {nullptr, nullptr};
7469 /// SCEV structural equivalence is usually sufficient for testing whether two
7470 /// expressions are equal, however for the purposes of looking for a condition
7471 /// guarding a loop, it can be useful to be a little more general, since a
7472 /// front-end may have replicated the controlling expression.
7474 static bool HasSameValue(const SCEV *A, const SCEV *B) {
7475 // Quick check to see if they are the same SCEV.
7476 if (A == B) return true;
7478 auto ComputesEqualValues = [](const Instruction *A, const Instruction *B) {
7479 // Not all instructions that are "identical" compute the same value. For
7480 // instance, two distinct alloca instructions allocating the same type are
7481 // identical and do not read memory; but compute distinct values.
7482 return A->isIdenticalTo(B) && (isa<BinaryOperator>(A) || isa<GetElementPtrInst>(A));
7485 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
7486 // two different instructions with the same value. Check for this case.
7487 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
7488 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
7489 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
7490 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
7491 if (ComputesEqualValues(AI, BI))
7494 // Otherwise assume they may have a different value.
7498 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
7499 const SCEV *&LHS, const SCEV *&RHS,
7501 bool Changed = false;
7503 // If we hit the max recursion limit bail out.
7507 // Canonicalize a constant to the right side.
7508 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
7509 // Check for both operands constant.
7510 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
7511 if (ConstantExpr::getICmp(Pred,
7513 RHSC->getValue())->isNullValue())
7514 goto trivially_false;
7516 goto trivially_true;
7518 // Otherwise swap the operands to put the constant on the right.
7519 std::swap(LHS, RHS);
7520 Pred = ICmpInst::getSwappedPredicate(Pred);
7524 // If we're comparing an addrec with a value which is loop-invariant in the
7525 // addrec's loop, put the addrec on the left. Also make a dominance check,
7526 // as both operands could be addrecs loop-invariant in each other's loop.
7527 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
7528 const Loop *L = AR->getLoop();
7529 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
7530 std::swap(LHS, RHS);
7531 Pred = ICmpInst::getSwappedPredicate(Pred);
7536 // If there's a constant operand, canonicalize comparisons with boundary
7537 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
7538 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
7539 const APInt &RA = RC->getAPInt();
7541 bool SimplifiedByConstantRange = false;
7543 if (!ICmpInst::isEquality(Pred)) {
7544 ConstantRange ExactCR = ConstantRange::makeExactICmpRegion(Pred, RA);
7545 if (ExactCR.isFullSet())
7546 goto trivially_true;
7547 else if (ExactCR.isEmptySet())
7548 goto trivially_false;
7551 CmpInst::Predicate NewPred;
7552 if (ExactCR.getEquivalentICmp(NewPred, NewRHS) &&
7553 ICmpInst::isEquality(NewPred)) {
7554 // We were able to convert an inequality to an equality.
7556 RHS = getConstant(NewRHS);
7557 Changed = SimplifiedByConstantRange = true;
7561 if (!SimplifiedByConstantRange) {
7565 case ICmpInst::ICMP_EQ:
7566 case ICmpInst::ICMP_NE:
7567 // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b.
7569 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS))
7570 if (const SCEVMulExpr *ME =
7571 dyn_cast<SCEVMulExpr>(AE->getOperand(0)))
7572 if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 &&
7573 ME->getOperand(0)->isAllOnesValue()) {
7574 RHS = AE->getOperand(1);
7575 LHS = ME->getOperand(1);
7581 // The "Should have been caught earlier!" messages refer to the fact
7582 // that the ExactCR.isFullSet() or ExactCR.isEmptySet() check above
7583 // should have fired on the corresponding cases, and canonicalized the
7584 // check to trivially_true or trivially_false.
7586 case ICmpInst::ICMP_UGE:
7587 assert(!RA.isMinValue() && "Should have been caught earlier!");
7588 Pred = ICmpInst::ICMP_UGT;
7589 RHS = getConstant(RA - 1);
7592 case ICmpInst::ICMP_ULE:
7593 assert(!RA.isMaxValue() && "Should have been caught earlier!");
7594 Pred = ICmpInst::ICMP_ULT;
7595 RHS = getConstant(RA + 1);
7598 case ICmpInst::ICMP_SGE:
7599 assert(!RA.isMinSignedValue() && "Should have been caught earlier!");
7600 Pred = ICmpInst::ICMP_SGT;
7601 RHS = getConstant(RA - 1);
7604 case ICmpInst::ICMP_SLE:
7605 assert(!RA.isMaxSignedValue() && "Should have been caught earlier!");
7606 Pred = ICmpInst::ICMP_SLT;
7607 RHS = getConstant(RA + 1);
7614 // Check for obvious equality.
7615 if (HasSameValue(LHS, RHS)) {
7616 if (ICmpInst::isTrueWhenEqual(Pred))
7617 goto trivially_true;
7618 if (ICmpInst::isFalseWhenEqual(Pred))
7619 goto trivially_false;
7622 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
7623 // adding or subtracting 1 from one of the operands.
7625 case ICmpInst::ICMP_SLE:
7626 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
7627 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
7629 Pred = ICmpInst::ICMP_SLT;
7631 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
7632 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
7634 Pred = ICmpInst::ICMP_SLT;
7638 case ICmpInst::ICMP_SGE:
7639 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
7640 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
7642 Pred = ICmpInst::ICMP_SGT;
7644 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
7645 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
7647 Pred = ICmpInst::ICMP_SGT;
7651 case ICmpInst::ICMP_ULE:
7652 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
7653 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
7655 Pred = ICmpInst::ICMP_ULT;
7657 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
7658 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS);
7659 Pred = ICmpInst::ICMP_ULT;
7663 case ICmpInst::ICMP_UGE:
7664 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
7665 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS);
7666 Pred = ICmpInst::ICMP_UGT;
7668 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
7669 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
7671 Pred = ICmpInst::ICMP_UGT;
7679 // TODO: More simplifications are possible here.
7681 // Recursively simplify until we either hit a recursion limit or nothing
7684 return SimplifyICmpOperands(Pred, LHS, RHS, Depth+1);
7690 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
7691 Pred = ICmpInst::ICMP_EQ;
7696 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
7697 Pred = ICmpInst::ICMP_NE;
7701 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
7702 return getSignedRange(S).getSignedMax().isNegative();
7705 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
7706 return getSignedRange(S).getSignedMin().isStrictlyPositive();
7709 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
7710 return !getSignedRange(S).getSignedMin().isNegative();
7713 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
7714 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
7717 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
7718 return isKnownNegative(S) || isKnownPositive(S);
7721 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
7722 const SCEV *LHS, const SCEV *RHS) {
7723 // Canonicalize the inputs first.
7724 (void)SimplifyICmpOperands(Pred, LHS, RHS);
7726 // If LHS or RHS is an addrec, check to see if the condition is true in
7727 // every iteration of the loop.
7728 // If LHS and RHS are both addrec, both conditions must be true in
7729 // every iteration of the loop.
7730 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
7731 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
7732 bool LeftGuarded = false;
7733 bool RightGuarded = false;
7735 const Loop *L = LAR->getLoop();
7736 if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
7737 isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
7738 if (!RAR) return true;
7743 const Loop *L = RAR->getLoop();
7744 if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
7745 isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
7746 if (!LAR) return true;
7747 RightGuarded = true;
7750 if (LeftGuarded && RightGuarded)
7753 if (isKnownPredicateViaSplitting(Pred, LHS, RHS))
7756 // Otherwise see what can be done with known constant ranges.
7757 return isKnownPredicateViaConstantRanges(Pred, LHS, RHS);
7760 bool ScalarEvolution::isMonotonicPredicate(const SCEVAddRecExpr *LHS,
7761 ICmpInst::Predicate Pred,
7763 bool Result = isMonotonicPredicateImpl(LHS, Pred, Increasing);
7766 // Verify an invariant: inverting the predicate should turn a monotonically
7767 // increasing change to a monotonically decreasing one, and vice versa.
7768 bool IncreasingSwapped;
7769 bool ResultSwapped = isMonotonicPredicateImpl(
7770 LHS, ICmpInst::getSwappedPredicate(Pred), IncreasingSwapped);
7772 assert(Result == ResultSwapped && "should be able to analyze both!");
7774 assert(Increasing == !IncreasingSwapped &&
7775 "monotonicity should flip as we flip the predicate");
7781 bool ScalarEvolution::isMonotonicPredicateImpl(const SCEVAddRecExpr *LHS,
7782 ICmpInst::Predicate Pred,
7785 // A zero step value for LHS means the induction variable is essentially a
7786 // loop invariant value. We don't really depend on the predicate actually
7787 // flipping from false to true (for increasing predicates, and the other way
7788 // around for decreasing predicates), all we care about is that *if* the
7789 // predicate changes then it only changes from false to true.
7791 // A zero step value in itself is not very useful, but there may be places
7792 // where SCEV can prove X >= 0 but not prove X > 0, so it is helpful to be
7793 // as general as possible.
7797 return false; // Conservative answer
7799 case ICmpInst::ICMP_UGT:
7800 case ICmpInst::ICMP_UGE:
7801 case ICmpInst::ICMP_ULT:
7802 case ICmpInst::ICMP_ULE:
7803 if (!LHS->hasNoUnsignedWrap())
7806 Increasing = Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE;
7809 case ICmpInst::ICMP_SGT:
7810 case ICmpInst::ICMP_SGE:
7811 case ICmpInst::ICMP_SLT:
7812 case ICmpInst::ICMP_SLE: {
7813 if (!LHS->hasNoSignedWrap())
7816 const SCEV *Step = LHS->getStepRecurrence(*this);
7818 if (isKnownNonNegative(Step)) {
7819 Increasing = Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE;
7823 if (isKnownNonPositive(Step)) {
7824 Increasing = Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE;
7833 llvm_unreachable("switch has default clause!");
7836 bool ScalarEvolution::isLoopInvariantPredicate(
7837 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, const Loop *L,
7838 ICmpInst::Predicate &InvariantPred, const SCEV *&InvariantLHS,
7839 const SCEV *&InvariantRHS) {
7841 // If there is a loop-invariant, force it into the RHS, otherwise bail out.
7842 if (!isLoopInvariant(RHS, L)) {
7843 if (!isLoopInvariant(LHS, L))
7846 std::swap(LHS, RHS);
7847 Pred = ICmpInst::getSwappedPredicate(Pred);
7850 const SCEVAddRecExpr *ArLHS = dyn_cast<SCEVAddRecExpr>(LHS);
7851 if (!ArLHS || ArLHS->getLoop() != L)
7855 if (!isMonotonicPredicate(ArLHS, Pred, Increasing))
7858 // If the predicate "ArLHS `Pred` RHS" monotonically increases from false to
7859 // true as the loop iterates, and the backedge is control dependent on
7860 // "ArLHS `Pred` RHS" == true then we can reason as follows:
7862 // * if the predicate was false in the first iteration then the predicate
7863 // is never evaluated again, since the loop exits without taking the
7865 // * if the predicate was true in the first iteration then it will
7866 // continue to be true for all future iterations since it is
7867 // monotonically increasing.
7869 // For both the above possibilities, we can replace the loop varying
7870 // predicate with its value on the first iteration of the loop (which is
7873 // A similar reasoning applies for a monotonically decreasing predicate, by
7874 // replacing true with false and false with true in the above two bullets.
7876 auto P = Increasing ? Pred : ICmpInst::getInversePredicate(Pred);
7878 if (!isLoopBackedgeGuardedByCond(L, P, LHS, RHS))
7881 InvariantPred = Pred;
7882 InvariantLHS = ArLHS->getStart();
7887 bool ScalarEvolution::isKnownPredicateViaConstantRanges(
7888 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) {
7889 if (HasSameValue(LHS, RHS))
7890 return ICmpInst::isTrueWhenEqual(Pred);
7892 // This code is split out from isKnownPredicate because it is called from
7893 // within isLoopEntryGuardedByCond.
7896 [&](const ConstantRange &RangeLHS, const ConstantRange &RangeRHS) {
7897 return ConstantRange::makeSatisfyingICmpRegion(Pred, RangeRHS)
7898 .contains(RangeLHS);
7901 // The check at the top of the function catches the case where the values are
7902 // known to be equal.
7903 if (Pred == CmpInst::ICMP_EQ)
7906 if (Pred == CmpInst::ICMP_NE)
7907 return CheckRanges(getSignedRange(LHS), getSignedRange(RHS)) ||
7908 CheckRanges(getUnsignedRange(LHS), getUnsignedRange(RHS)) ||
7909 isKnownNonZero(getMinusSCEV(LHS, RHS));
7911 if (CmpInst::isSigned(Pred))
7912 return CheckRanges(getSignedRange(LHS), getSignedRange(RHS));
7914 return CheckRanges(getUnsignedRange(LHS), getUnsignedRange(RHS));
7917 bool ScalarEvolution::isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred,
7921 // Match Result to (X + Y)<ExpectedFlags> where Y is a constant integer.
7922 // Return Y via OutY.
7923 auto MatchBinaryAddToConst =
7924 [this](const SCEV *Result, const SCEV *X, APInt &OutY,
7925 SCEV::NoWrapFlags ExpectedFlags) {
7926 const SCEV *NonConstOp, *ConstOp;
7927 SCEV::NoWrapFlags FlagsPresent;
7929 if (!splitBinaryAdd(Result, ConstOp, NonConstOp, FlagsPresent) ||
7930 !isa<SCEVConstant>(ConstOp) || NonConstOp != X)
7933 OutY = cast<SCEVConstant>(ConstOp)->getAPInt();
7934 return (FlagsPresent & ExpectedFlags) == ExpectedFlags;
7943 case ICmpInst::ICMP_SGE:
7944 std::swap(LHS, RHS);
7945 case ICmpInst::ICMP_SLE:
7946 // X s<= (X + C)<nsw> if C >= 0
7947 if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) && C.isNonNegative())
7950 // (X + C)<nsw> s<= X if C <= 0
7951 if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) &&
7952 !C.isStrictlyPositive())
7956 case ICmpInst::ICMP_SGT:
7957 std::swap(LHS, RHS);
7958 case ICmpInst::ICMP_SLT:
7959 // X s< (X + C)<nsw> if C > 0
7960 if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) &&
7961 C.isStrictlyPositive())
7964 // (X + C)<nsw> s< X if C < 0
7965 if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) && C.isNegative())
7973 bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred,
7976 if (Pred != ICmpInst::ICMP_ULT || ProvingSplitPredicate)
7979 // Allowing arbitrary number of activations of isKnownPredicateViaSplitting on
7980 // the stack can result in exponential time complexity.
7981 SaveAndRestore<bool> Restore(ProvingSplitPredicate, true);
7983 // If L >= 0 then I `ult` L <=> I >= 0 && I `slt` L
7985 // To prove L >= 0 we use isKnownNonNegative whereas to prove I >= 0 we use
7986 // isKnownPredicate. isKnownPredicate is more powerful, but also more
7987 // expensive; and using isKnownNonNegative(RHS) is sufficient for most of the
7988 // interesting cases seen in practice. We can consider "upgrading" L >= 0 to
7989 // use isKnownPredicate later if needed.
7990 return isKnownNonNegative(RHS) &&
7991 isKnownPredicate(CmpInst::ICMP_SGE, LHS, getZero(LHS->getType())) &&
7992 isKnownPredicate(CmpInst::ICMP_SLT, LHS, RHS);
7995 bool ScalarEvolution::isImpliedViaGuard(BasicBlock *BB,
7996 ICmpInst::Predicate Pred,
7997 const SCEV *LHS, const SCEV *RHS) {
7998 // No need to even try if we know the module has no guards.
8002 return any_of(*BB, [&](Instruction &I) {
8003 using namespace llvm::PatternMatch;
8006 return match(&I, m_Intrinsic<Intrinsic::experimental_guard>(
8007 m_Value(Condition))) &&
8008 isImpliedCond(Pred, LHS, RHS, Condition, false);
8012 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
8013 /// protected by a conditional between LHS and RHS. This is used to
8014 /// to eliminate casts.
8016 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
8017 ICmpInst::Predicate Pred,
8018 const SCEV *LHS, const SCEV *RHS) {
8019 // Interpret a null as meaning no loop, where there is obviously no guard
8020 // (interprocedural conditions notwithstanding).
8021 if (!L) return true;
8023 if (isKnownPredicateViaConstantRanges(Pred, LHS, RHS))
8026 BasicBlock *Latch = L->getLoopLatch();
8030 BranchInst *LoopContinuePredicate =
8031 dyn_cast<BranchInst>(Latch->getTerminator());
8032 if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
8033 isImpliedCond(Pred, LHS, RHS,
8034 LoopContinuePredicate->getCondition(),
8035 LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
8038 // We don't want more than one activation of the following loops on the stack
8039 // -- that can lead to O(n!) time complexity.
8040 if (WalkingBEDominatingConds)
8043 SaveAndRestore<bool> ClearOnExit(WalkingBEDominatingConds, true);
8045 // See if we can exploit a trip count to prove the predicate.
8046 const auto &BETakenInfo = getBackedgeTakenInfo(L);
8047 const SCEV *LatchBECount = BETakenInfo.getExact(Latch, this);
8048 if (LatchBECount != getCouldNotCompute()) {
8049 // We know that Latch branches back to the loop header exactly
8050 // LatchBECount times. This means the backdege condition at Latch is
8051 // equivalent to "{0,+,1} u< LatchBECount".
8052 Type *Ty = LatchBECount->getType();
8053 auto NoWrapFlags = SCEV::NoWrapFlags(SCEV::FlagNUW | SCEV::FlagNW);
8054 const SCEV *LoopCounter =
8055 getAddRecExpr(getZero(Ty), getOne(Ty), L, NoWrapFlags);
8056 if (isImpliedCond(Pred, LHS, RHS, ICmpInst::ICMP_ULT, LoopCounter,
8061 // Check conditions due to any @llvm.assume intrinsics.
8062 for (auto &AssumeVH : AC.assumptions()) {
8065 auto *CI = cast<CallInst>(AssumeVH);
8066 if (!DT.dominates(CI, Latch->getTerminator()))
8069 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
8073 // If the loop is not reachable from the entry block, we risk running into an
8074 // infinite loop as we walk up into the dom tree. These loops do not matter
8075 // anyway, so we just return a conservative answer when we see them.
8076 if (!DT.isReachableFromEntry(L->getHeader()))
8079 if (isImpliedViaGuard(Latch, Pred, LHS, RHS))
8082 for (DomTreeNode *DTN = DT[Latch], *HeaderDTN = DT[L->getHeader()];
8083 DTN != HeaderDTN; DTN = DTN->getIDom()) {
8085 assert(DTN && "should reach the loop header before reaching the root!");
8087 BasicBlock *BB = DTN->getBlock();
8088 if (isImpliedViaGuard(BB, Pred, LHS, RHS))
8091 BasicBlock *PBB = BB->getSinglePredecessor();
8095 BranchInst *ContinuePredicate = dyn_cast<BranchInst>(PBB->getTerminator());
8096 if (!ContinuePredicate || !ContinuePredicate->isConditional())
8099 Value *Condition = ContinuePredicate->getCondition();
8101 // If we have an edge `E` within the loop body that dominates the only
8102 // latch, the condition guarding `E` also guards the backedge. This
8103 // reasoning works only for loops with a single latch.
8105 BasicBlockEdge DominatingEdge(PBB, BB);
8106 if (DominatingEdge.isSingleEdge()) {
8107 // We're constructively (and conservatively) enumerating edges within the
8108 // loop body that dominate the latch. The dominator tree better agree
8110 assert(DT.dominates(DominatingEdge, Latch) && "should be!");
8112 if (isImpliedCond(Pred, LHS, RHS, Condition,
8113 BB != ContinuePredicate->getSuccessor(0)))
8122 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
8123 ICmpInst::Predicate Pred,
8124 const SCEV *LHS, const SCEV *RHS) {
8125 // Interpret a null as meaning no loop, where there is obviously no guard
8126 // (interprocedural conditions notwithstanding).
8127 if (!L) return false;
8129 if (isKnownPredicateViaConstantRanges(Pred, LHS, RHS))
8132 // Starting at the loop predecessor, climb up the predecessor chain, as long
8133 // as there are predecessors that can be found that have unique successors
8134 // leading to the original header.
8135 for (std::pair<BasicBlock *, BasicBlock *>
8136 Pair(L->getLoopPredecessor(), L->getHeader());
8138 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
8140 if (isImpliedViaGuard(Pair.first, Pred, LHS, RHS))
8143 BranchInst *LoopEntryPredicate =
8144 dyn_cast<BranchInst>(Pair.first->getTerminator());
8145 if (!LoopEntryPredicate ||
8146 LoopEntryPredicate->isUnconditional())
8149 if (isImpliedCond(Pred, LHS, RHS,
8150 LoopEntryPredicate->getCondition(),
8151 LoopEntryPredicate->getSuccessor(0) != Pair.second))
8155 // Check conditions due to any @llvm.assume intrinsics.
8156 for (auto &AssumeVH : AC.assumptions()) {
8159 auto *CI = cast<CallInst>(AssumeVH);
8160 if (!DT.dominates(CI, L->getHeader()))
8163 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
8170 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
8171 const SCEV *LHS, const SCEV *RHS,
8172 Value *FoundCondValue,
8174 if (!PendingLoopPredicates.insert(FoundCondValue).second)
8178 make_scope_exit([&]() { PendingLoopPredicates.erase(FoundCondValue); });
8180 // Recursively handle And and Or conditions.
8181 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
8182 if (BO->getOpcode() == Instruction::And) {
8184 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
8185 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
8186 } else if (BO->getOpcode() == Instruction::Or) {
8188 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
8189 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
8193 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
8194 if (!ICI) return false;
8196 // Now that we found a conditional branch that dominates the loop or controls
8197 // the loop latch. Check to see if it is the comparison we are looking for.
8198 ICmpInst::Predicate FoundPred;
8200 FoundPred = ICI->getInversePredicate();
8202 FoundPred = ICI->getPredicate();
8204 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
8205 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
8207 return isImpliedCond(Pred, LHS, RHS, FoundPred, FoundLHS, FoundRHS);
8210 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS,
8212 ICmpInst::Predicate FoundPred,
8213 const SCEV *FoundLHS,
8214 const SCEV *FoundRHS) {
8215 // Balance the types.
8216 if (getTypeSizeInBits(LHS->getType()) <
8217 getTypeSizeInBits(FoundLHS->getType())) {
8218 if (CmpInst::isSigned(Pred)) {
8219 LHS = getSignExtendExpr(LHS, FoundLHS->getType());
8220 RHS = getSignExtendExpr(RHS, FoundLHS->getType());
8222 LHS = getZeroExtendExpr(LHS, FoundLHS->getType());
8223 RHS = getZeroExtendExpr(RHS, FoundLHS->getType());
8225 } else if (getTypeSizeInBits(LHS->getType()) >
8226 getTypeSizeInBits(FoundLHS->getType())) {
8227 if (CmpInst::isSigned(FoundPred)) {
8228 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
8229 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
8231 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
8232 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
8236 // Canonicalize the query to match the way instcombine will have
8237 // canonicalized the comparison.
8238 if (SimplifyICmpOperands(Pred, LHS, RHS))
8240 return CmpInst::isTrueWhenEqual(Pred);
8241 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
8242 if (FoundLHS == FoundRHS)
8243 return CmpInst::isFalseWhenEqual(FoundPred);
8245 // Check to see if we can make the LHS or RHS match.
8246 if (LHS == FoundRHS || RHS == FoundLHS) {
8247 if (isa<SCEVConstant>(RHS)) {
8248 std::swap(FoundLHS, FoundRHS);
8249 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
8251 std::swap(LHS, RHS);
8252 Pred = ICmpInst::getSwappedPredicate(Pred);
8256 // Check whether the found predicate is the same as the desired predicate.
8257 if (FoundPred == Pred)
8258 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
8260 // Check whether swapping the found predicate makes it the same as the
8261 // desired predicate.
8262 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
8263 if (isa<SCEVConstant>(RHS))
8264 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
8266 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
8267 RHS, LHS, FoundLHS, FoundRHS);
8270 // Unsigned comparison is the same as signed comparison when both the operands
8271 // are non-negative.
8272 if (CmpInst::isUnsigned(FoundPred) &&
8273 CmpInst::getSignedPredicate(FoundPred) == Pred &&
8274 isKnownNonNegative(FoundLHS) && isKnownNonNegative(FoundRHS))
8275 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
8277 // Check if we can make progress by sharpening ranges.
8278 if (FoundPred == ICmpInst::ICMP_NE &&
8279 (isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) {
8281 const SCEVConstant *C = nullptr;
8282 const SCEV *V = nullptr;
8284 if (isa<SCEVConstant>(FoundLHS)) {
8285 C = cast<SCEVConstant>(FoundLHS);
8288 C = cast<SCEVConstant>(FoundRHS);
8292 // The guarding predicate tells us that C != V. If the known range
8293 // of V is [C, t), we can sharpen the range to [C + 1, t). The
8294 // range we consider has to correspond to same signedness as the
8295 // predicate we're interested in folding.
8297 APInt Min = ICmpInst::isSigned(Pred) ?
8298 getSignedRange(V).getSignedMin() : getUnsignedRange(V).getUnsignedMin();
8300 if (Min == C->getAPInt()) {
8301 // Given (V >= Min && V != Min) we conclude V >= (Min + 1).
8302 // This is true even if (Min + 1) wraps around -- in case of
8303 // wraparound, (Min + 1) < Min, so (V >= Min => V >= (Min + 1)).
8305 APInt SharperMin = Min + 1;
8308 case ICmpInst::ICMP_SGE:
8309 case ICmpInst::ICMP_UGE:
8310 // We know V `Pred` SharperMin. If this implies LHS `Pred`
8312 if (isImpliedCondOperands(Pred, LHS, RHS, V,
8313 getConstant(SharperMin)))
8316 case ICmpInst::ICMP_SGT:
8317 case ICmpInst::ICMP_UGT:
8318 // We know from the range information that (V `Pred` Min ||
8319 // V == Min). We know from the guarding condition that !(V
8320 // == Min). This gives us
8322 // V `Pred` Min || V == Min && !(V == Min)
8325 // If V `Pred` Min implies LHS `Pred` RHS, we're done.
8327 if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min)))
8337 // Check whether the actual condition is beyond sufficient.
8338 if (FoundPred == ICmpInst::ICMP_EQ)
8339 if (ICmpInst::isTrueWhenEqual(Pred))
8340 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
8342 if (Pred == ICmpInst::ICMP_NE)
8343 if (!ICmpInst::isTrueWhenEqual(FoundPred))
8344 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
8347 // Otherwise assume the worst.
8351 bool ScalarEvolution::splitBinaryAdd(const SCEV *Expr,
8352 const SCEV *&L, const SCEV *&R,
8353 SCEV::NoWrapFlags &Flags) {
8354 const auto *AE = dyn_cast<SCEVAddExpr>(Expr);
8355 if (!AE || AE->getNumOperands() != 2)
8358 L = AE->getOperand(0);
8359 R = AE->getOperand(1);
8360 Flags = AE->getNoWrapFlags();
8364 Optional<APInt> ScalarEvolution::computeConstantDifference(const SCEV *More,
8366 // We avoid subtracting expressions here because this function is usually
8367 // fairly deep in the call stack (i.e. is called many times).
8369 if (isa<SCEVAddRecExpr>(Less) && isa<SCEVAddRecExpr>(More)) {
8370 const auto *LAR = cast<SCEVAddRecExpr>(Less);
8371 const auto *MAR = cast<SCEVAddRecExpr>(More);
8373 if (LAR->getLoop() != MAR->getLoop())
8376 // We look at affine expressions only; not for correctness but to keep
8377 // getStepRecurrence cheap.
8378 if (!LAR->isAffine() || !MAR->isAffine())
8381 if (LAR->getStepRecurrence(*this) != MAR->getStepRecurrence(*this))
8384 Less = LAR->getStart();
8385 More = MAR->getStart();
8390 if (isa<SCEVConstant>(Less) && isa<SCEVConstant>(More)) {
8391 const auto &M = cast<SCEVConstant>(More)->getAPInt();
8392 const auto &L = cast<SCEVConstant>(Less)->getAPInt();
8397 SCEV::NoWrapFlags Flags;
8398 if (splitBinaryAdd(Less, L, R, Flags))
8399 if (const auto *LC = dyn_cast<SCEVConstant>(L))
8401 return -(LC->getAPInt());
8403 if (splitBinaryAdd(More, L, R, Flags))
8404 if (const auto *LC = dyn_cast<SCEVConstant>(L))
8406 return LC->getAPInt();
8411 bool ScalarEvolution::isImpliedCondOperandsViaNoOverflow(
8412 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS,
8413 const SCEV *FoundLHS, const SCEV *FoundRHS) {
8414 if (Pred != CmpInst::ICMP_SLT && Pred != CmpInst::ICMP_ULT)
8417 const auto *AddRecLHS = dyn_cast<SCEVAddRecExpr>(LHS);
8421 const auto *AddRecFoundLHS = dyn_cast<SCEVAddRecExpr>(FoundLHS);
8422 if (!AddRecFoundLHS)
8425 // We'd like to let SCEV reason about control dependencies, so we constrain
8426 // both the inequalities to be about add recurrences on the same loop. This
8427 // way we can use isLoopEntryGuardedByCond later.
8429 const Loop *L = AddRecFoundLHS->getLoop();
8430 if (L != AddRecLHS->getLoop())
8433 // FoundLHS u< FoundRHS u< -C => (FoundLHS + C) u< (FoundRHS + C) ... (1)
8435 // FoundLHS s< FoundRHS s< INT_MIN - C => (FoundLHS + C) s< (FoundRHS + C)
8438 // Informal proof for (2), assuming (1) [*]:
8440 // We'll also assume (A s< B) <=> ((A + INT_MIN) u< (B + INT_MIN)) ... (3)[**]
8444 // FoundLHS s< FoundRHS s< INT_MIN - C
8445 // <=> (FoundLHS + INT_MIN) u< (FoundRHS + INT_MIN) u< -C [ using (3) ]
8446 // <=> (FoundLHS + INT_MIN + C) u< (FoundRHS + INT_MIN + C) [ using (1) ]
8447 // <=> (FoundLHS + INT_MIN + C + INT_MIN) s<
8448 // (FoundRHS + INT_MIN + C + INT_MIN) [ using (3) ]
8449 // <=> FoundLHS + C s< FoundRHS + C
8451 // [*]: (1) can be proved by ruling out overflow.
8453 // [**]: This can be proved by analyzing all the four possibilities:
8454 // (A s< 0, B s< 0), (A s< 0, B s>= 0), (A s>= 0, B s< 0) and
8455 // (A s>= 0, B s>= 0).
8458 // Despite (2), "FoundRHS s< INT_MIN - C" does not mean that "FoundRHS + C"
8459 // will not sign underflow. For instance, say FoundLHS = (i8 -128), FoundRHS
8460 // = (i8 -127) and C = (i8 -100). Then INT_MIN - C = (i8 -28), and FoundRHS
8461 // s< (INT_MIN - C). Lack of sign overflow / underflow in "FoundRHS + C" is
8462 // neither necessary nor sufficient to prove "(FoundLHS + C) s< (FoundRHS +
8465 Optional<APInt> LDiff = computeConstantDifference(LHS, FoundLHS);
8466 Optional<APInt> RDiff = computeConstantDifference(RHS, FoundRHS);
8467 if (!LDiff || !RDiff || *LDiff != *RDiff)
8470 if (LDiff->isMinValue())
8473 APInt FoundRHSLimit;
8475 if (Pred == CmpInst::ICMP_ULT) {
8476 FoundRHSLimit = -(*RDiff);
8478 assert(Pred == CmpInst::ICMP_SLT && "Checked above!");
8479 FoundRHSLimit = APInt::getSignedMinValue(getTypeSizeInBits(RHS->getType())) - *RDiff;
8482 // Try to prove (1) or (2), as needed.
8483 return isLoopEntryGuardedByCond(L, Pred, FoundRHS,
8484 getConstant(FoundRHSLimit));
8487 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
8488 const SCEV *LHS, const SCEV *RHS,
8489 const SCEV *FoundLHS,
8490 const SCEV *FoundRHS) {
8491 if (isImpliedCondOperandsViaRanges(Pred, LHS, RHS, FoundLHS, FoundRHS))
8494 if (isImpliedCondOperandsViaNoOverflow(Pred, LHS, RHS, FoundLHS, FoundRHS))
8497 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
8498 FoundLHS, FoundRHS) ||
8499 // ~x < ~y --> x > y
8500 isImpliedCondOperandsHelper(Pred, LHS, RHS,
8501 getNotSCEV(FoundRHS),
8502 getNotSCEV(FoundLHS));
8506 /// If Expr computes ~A, return A else return nullptr
8507 static const SCEV *MatchNotExpr(const SCEV *Expr) {
8508 const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Expr);
8509 if (!Add || Add->getNumOperands() != 2 ||
8510 !Add->getOperand(0)->isAllOnesValue())
8513 const SCEVMulExpr *AddRHS = dyn_cast<SCEVMulExpr>(Add->getOperand(1));
8514 if (!AddRHS || AddRHS->getNumOperands() != 2 ||
8515 !AddRHS->getOperand(0)->isAllOnesValue())
8518 return AddRHS->getOperand(1);
8522 /// Is MaybeMaxExpr an SMax or UMax of Candidate and some other values?
8523 template<typename MaxExprType>
8524 static bool IsMaxConsistingOf(const SCEV *MaybeMaxExpr,
8525 const SCEV *Candidate) {
8526 const MaxExprType *MaxExpr = dyn_cast<MaxExprType>(MaybeMaxExpr);
8527 if (!MaxExpr) return false;
8529 return find(MaxExpr->operands(), Candidate) != MaxExpr->op_end();
8533 /// Is MaybeMinExpr an SMin or UMin of Candidate and some other values?
8534 template<typename MaxExprType>
8535 static bool IsMinConsistingOf(ScalarEvolution &SE,
8536 const SCEV *MaybeMinExpr,
8537 const SCEV *Candidate) {
8538 const SCEV *MaybeMaxExpr = MatchNotExpr(MaybeMinExpr);
8542 return IsMaxConsistingOf<MaxExprType>(MaybeMaxExpr, SE.getNotSCEV(Candidate));
8545 static bool IsKnownPredicateViaAddRecStart(ScalarEvolution &SE,
8546 ICmpInst::Predicate Pred,
8547 const SCEV *LHS, const SCEV *RHS) {
8549 // If both sides are affine addrecs for the same loop, with equal
8550 // steps, and we know the recurrences don't wrap, then we only
8551 // need to check the predicate on the starting values.
8553 if (!ICmpInst::isRelational(Pred))
8556 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
8559 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
8562 if (LAR->getLoop() != RAR->getLoop())
8564 if (!LAR->isAffine() || !RAR->isAffine())
8567 if (LAR->getStepRecurrence(SE) != RAR->getStepRecurrence(SE))
8570 SCEV::NoWrapFlags NW = ICmpInst::isSigned(Pred) ?
8571 SCEV::FlagNSW : SCEV::FlagNUW;
8572 if (!LAR->getNoWrapFlags(NW) || !RAR->getNoWrapFlags(NW))
8575 return SE.isKnownPredicate(Pred, LAR->getStart(), RAR->getStart());
8578 /// Is LHS `Pred` RHS true on the virtue of LHS or RHS being a Min or Max
8580 static bool IsKnownPredicateViaMinOrMax(ScalarEvolution &SE,
8581 ICmpInst::Predicate Pred,
8582 const SCEV *LHS, const SCEV *RHS) {
8587 case ICmpInst::ICMP_SGE:
8588 std::swap(LHS, RHS);
8590 case ICmpInst::ICMP_SLE:
8593 IsMinConsistingOf<SCEVSMaxExpr>(SE, LHS, RHS) ||
8595 IsMaxConsistingOf<SCEVSMaxExpr>(RHS, LHS);
8597 case ICmpInst::ICMP_UGE:
8598 std::swap(LHS, RHS);
8600 case ICmpInst::ICMP_ULE:
8603 IsMinConsistingOf<SCEVUMaxExpr>(SE, LHS, RHS) ||
8605 IsMaxConsistingOf<SCEVUMaxExpr>(RHS, LHS);
8608 llvm_unreachable("covered switch fell through?!");
8611 bool ScalarEvolution::isImpliedViaOperations(ICmpInst::Predicate Pred,
8612 const SCEV *LHS, const SCEV *RHS,
8613 const SCEV *FoundLHS,
8614 const SCEV *FoundRHS,
8616 assert(getTypeSizeInBits(LHS->getType()) ==
8617 getTypeSizeInBits(RHS->getType()) &&
8618 "LHS and RHS have different sizes?");
8619 assert(getTypeSizeInBits(FoundLHS->getType()) ==
8620 getTypeSizeInBits(FoundRHS->getType()) &&
8621 "FoundLHS and FoundRHS have different sizes?");
8622 // We want to avoid hurting the compile time with analysis of too big trees.
8623 if (Depth > MaxSCEVOperationsImplicationDepth)
8625 // We only want to work with ICMP_SGT comparison so far.
8626 // TODO: Extend to ICMP_UGT?
8627 if (Pred == ICmpInst::ICMP_SLT) {
8628 Pred = ICmpInst::ICMP_SGT;
8629 std::swap(LHS, RHS);
8630 std::swap(FoundLHS, FoundRHS);
8632 if (Pred != ICmpInst::ICMP_SGT)
8635 auto GetOpFromSExt = [&](const SCEV *S) {
8636 if (auto *Ext = dyn_cast<SCEVSignExtendExpr>(S))
8637 return Ext->getOperand();
8638 // TODO: If S is a SCEVConstant then you can cheaply "strip" the sext off
8639 // the constant in some cases.
8643 // Acquire values from extensions.
8644 auto *OrigFoundLHS = FoundLHS;
8645 LHS = GetOpFromSExt(LHS);
8646 FoundLHS = GetOpFromSExt(FoundLHS);
8648 // Is the SGT predicate can be proved trivially or using the found context.
8649 auto IsSGTViaContext = [&](const SCEV *S1, const SCEV *S2) {
8650 return isKnownViaSimpleReasoning(ICmpInst::ICMP_SGT, S1, S2) ||
8651 isImpliedViaOperations(ICmpInst::ICMP_SGT, S1, S2, OrigFoundLHS,
8652 FoundRHS, Depth + 1);
8655 if (auto *LHSAddExpr = dyn_cast<SCEVAddExpr>(LHS)) {
8656 // We want to avoid creation of any new non-constant SCEV. Since we are
8657 // going to compare the operands to RHS, we should be certain that we don't
8658 // need any size extensions for this. So let's decline all cases when the
8659 // sizes of types of LHS and RHS do not match.
8660 // TODO: Maybe try to get RHS from sext to catch more cases?
8661 if (getTypeSizeInBits(LHS->getType()) != getTypeSizeInBits(RHS->getType()))
8664 // Should not overflow.
8665 if (!LHSAddExpr->hasNoSignedWrap())
8668 auto *LL = LHSAddExpr->getOperand(0);
8669 auto *LR = LHSAddExpr->getOperand(1);
8670 auto *MinusOne = getNegativeSCEV(getOne(RHS->getType()));
8672 // Checks that S1 >= 0 && S2 > RHS, trivially or using the found context.
8673 auto IsSumGreaterThanRHS = [&](const SCEV *S1, const SCEV *S2) {
8674 return IsSGTViaContext(S1, MinusOne) && IsSGTViaContext(S2, RHS);
8676 // Try to prove the following rule:
8677 // (LHS = LL + LR) && (LL >= 0) && (LR > RHS) => (LHS > RHS).
8678 // (LHS = LL + LR) && (LR >= 0) && (LL > RHS) => (LHS > RHS).
8679 if (IsSumGreaterThanRHS(LL, LR) || IsSumGreaterThanRHS(LR, LL))
8681 } else if (auto *LHSUnknownExpr = dyn_cast<SCEVUnknown>(LHS)) {
8683 // FIXME: Once we have SDiv implemented, we can get rid of this matching.
8684 using namespace llvm::PatternMatch;
8685 if (match(LHSUnknownExpr->getValue(), m_SDiv(m_Value(LL), m_Value(LR)))) {
8686 // Rules for division.
8687 // We are going to perform some comparisons with Denominator and its
8688 // derivative expressions. In general case, creating a SCEV for it may
8689 // lead to a complex analysis of the entire graph, and in particular it
8690 // can request trip count recalculation for the same loop. This would
8691 // cache as SCEVCouldNotCompute to avoid the infinite recursion. To avoid
8692 // this, we only want to create SCEVs that are constants in this section.
8693 // So we bail if Denominator is not a constant.
8694 if (!isa<ConstantInt>(LR))
8697 auto *Denominator = cast<SCEVConstant>(getSCEV(LR));
8699 // We want to make sure that LHS = FoundLHS / Denominator. If it is so,
8700 // then a SCEV for the numerator already exists and matches with FoundLHS.
8701 auto *Numerator = getExistingSCEV(LL);
8702 if (!Numerator || Numerator->getType() != FoundLHS->getType())
8705 // Make sure that the numerator matches with FoundLHS and the denominator
8707 if (!HasSameValue(Numerator, FoundLHS) || !isKnownPositive(Denominator))
8710 auto *DTy = Denominator->getType();
8711 auto *FRHSTy = FoundRHS->getType();
8712 if (DTy->isPointerTy() != FRHSTy->isPointerTy())
8713 // One of types is a pointer and another one is not. We cannot extend
8714 // them properly to a wider type, so let us just reject this case.
8715 // TODO: Usage of getEffectiveSCEVType for DTy, FRHSTy etc should help
8716 // to avoid this check.
8720 // FoundLHS > FoundRHS, LHS = FoundLHS / Denominator, Denominator > 0.
8721 auto *WTy = getWiderType(DTy, FRHSTy);
8722 auto *DenominatorExt = getNoopOrSignExtend(Denominator, WTy);
8723 auto *FoundRHSExt = getNoopOrSignExtend(FoundRHS, WTy);
8725 // Try to prove the following rule:
8726 // (FoundRHS > Denominator - 2) && (RHS <= 0) => (LHS > RHS).
8727 // For example, given that FoundLHS > 2. It means that FoundLHS is at
8728 // least 3. If we divide it by Denominator < 4, we will have at least 1.
8729 auto *DenomMinusTwo = getMinusSCEV(DenominatorExt, getConstant(WTy, 2));
8730 if (isKnownNonPositive(RHS) &&
8731 IsSGTViaContext(FoundRHSExt, DenomMinusTwo))
8734 // Try to prove the following rule:
8735 // (FoundRHS > -1 - Denominator) && (RHS < 0) => (LHS > RHS).
8736 // For example, given that FoundLHS > -3. Then FoundLHS is at least -2.
8737 // If we divide it by Denominator > 2, then:
8738 // 1. If FoundLHS is negative, then the result is 0.
8739 // 2. If FoundLHS is non-negative, then the result is non-negative.
8740 // Anyways, the result is non-negative.
8741 auto *MinusOne = getNegativeSCEV(getOne(WTy));
8742 auto *NegDenomMinusOne = getMinusSCEV(MinusOne, DenominatorExt);
8743 if (isKnownNegative(RHS) &&
8744 IsSGTViaContext(FoundRHSExt, NegDenomMinusOne))
8753 ScalarEvolution::isKnownViaSimpleReasoning(ICmpInst::Predicate Pred,
8754 const SCEV *LHS, const SCEV *RHS) {
8755 return isKnownPredicateViaConstantRanges(Pred, LHS, RHS) ||
8756 IsKnownPredicateViaMinOrMax(*this, Pred, LHS, RHS) ||
8757 IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS) ||
8758 isKnownPredicateViaNoOverflow(Pred, LHS, RHS);
8762 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
8763 const SCEV *LHS, const SCEV *RHS,
8764 const SCEV *FoundLHS,
8765 const SCEV *FoundRHS) {
8767 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
8768 case ICmpInst::ICMP_EQ:
8769 case ICmpInst::ICMP_NE:
8770 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
8773 case ICmpInst::ICMP_SLT:
8774 case ICmpInst::ICMP_SLE:
8775 if (isKnownViaSimpleReasoning(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
8776 isKnownViaSimpleReasoning(ICmpInst::ICMP_SGE, RHS, FoundRHS))
8779 case ICmpInst::ICMP_SGT:
8780 case ICmpInst::ICMP_SGE:
8781 if (isKnownViaSimpleReasoning(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
8782 isKnownViaSimpleReasoning(ICmpInst::ICMP_SLE, RHS, FoundRHS))
8785 case ICmpInst::ICMP_ULT:
8786 case ICmpInst::ICMP_ULE:
8787 if (isKnownViaSimpleReasoning(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
8788 isKnownViaSimpleReasoning(ICmpInst::ICMP_UGE, RHS, FoundRHS))
8791 case ICmpInst::ICMP_UGT:
8792 case ICmpInst::ICMP_UGE:
8793 if (isKnownViaSimpleReasoning(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
8794 isKnownViaSimpleReasoning(ICmpInst::ICMP_ULE, RHS, FoundRHS))
8799 // Maybe it can be proved via operations?
8800 if (isImpliedViaOperations(Pred, LHS, RHS, FoundLHS, FoundRHS))
8806 bool ScalarEvolution::isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred,
8809 const SCEV *FoundLHS,
8810 const SCEV *FoundRHS) {
8811 if (!isa<SCEVConstant>(RHS) || !isa<SCEVConstant>(FoundRHS))
8812 // The restriction on `FoundRHS` be lifted easily -- it exists only to
8813 // reduce the compile time impact of this optimization.
8816 Optional<APInt> Addend = computeConstantDifference(LHS, FoundLHS);
8820 APInt ConstFoundRHS = cast<SCEVConstant>(FoundRHS)->getAPInt();
8822 // `FoundLHSRange` is the range we know `FoundLHS` to be in by virtue of the
8823 // antecedent "`FoundLHS` `Pred` `FoundRHS`".
8824 ConstantRange FoundLHSRange =
8825 ConstantRange::makeAllowedICmpRegion(Pred, ConstFoundRHS);
8827 // Since `LHS` is `FoundLHS` + `Addend`, we can compute a range for `LHS`:
8828 ConstantRange LHSRange = FoundLHSRange.add(ConstantRange(*Addend));
8830 // We can also compute the range of values for `LHS` that satisfy the
8831 // consequent, "`LHS` `Pred` `RHS`":
8832 APInt ConstRHS = cast<SCEVConstant>(RHS)->getAPInt();
8833 ConstantRange SatisfyingLHSRange =
8834 ConstantRange::makeSatisfyingICmpRegion(Pred, ConstRHS);
8836 // The antecedent implies the consequent if every value of `LHS` that
8837 // satisfies the antecedent also satisfies the consequent.
8838 return SatisfyingLHSRange.contains(LHSRange);
8841 bool ScalarEvolution::doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride,
8842 bool IsSigned, bool NoWrap) {
8843 assert(isKnownPositive(Stride) && "Positive stride expected!");
8845 if (NoWrap) return false;
8847 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
8848 const SCEV *One = getOne(Stride->getType());
8851 APInt MaxRHS = getSignedRange(RHS).getSignedMax();
8852 APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
8853 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
8856 // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow!
8857 return (MaxValue - MaxStrideMinusOne).slt(MaxRHS);
8860 APInt MaxRHS = getUnsignedRange(RHS).getUnsignedMax();
8861 APInt MaxValue = APInt::getMaxValue(BitWidth);
8862 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
8865 // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow!
8866 return (MaxValue - MaxStrideMinusOne).ult(MaxRHS);
8869 bool ScalarEvolution::doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride,
8870 bool IsSigned, bool NoWrap) {
8871 if (NoWrap) return false;
8873 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
8874 const SCEV *One = getOne(Stride->getType());
8877 APInt MinRHS = getSignedRange(RHS).getSignedMin();
8878 APInt MinValue = APInt::getSignedMinValue(BitWidth);
8879 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
8882 // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow!
8883 return (MinValue + MaxStrideMinusOne).sgt(MinRHS);
8886 APInt MinRHS = getUnsignedRange(RHS).getUnsignedMin();
8887 APInt MinValue = APInt::getMinValue(BitWidth);
8888 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
8891 // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow!
8892 return (MinValue + MaxStrideMinusOne).ugt(MinRHS);
8895 const SCEV *ScalarEvolution::computeBECount(const SCEV *Delta, const SCEV *Step,
8897 const SCEV *One = getOne(Step->getType());
8898 Delta = Equality ? getAddExpr(Delta, Step)
8899 : getAddExpr(Delta, getMinusSCEV(Step, One));
8900 return getUDivExpr(Delta, Step);
8903 ScalarEvolution::ExitLimit
8904 ScalarEvolution::howManyLessThans(const SCEV *LHS, const SCEV *RHS,
8905 const Loop *L, bool IsSigned,
8906 bool ControlsExit, bool AllowPredicates) {
8907 SmallPtrSet<const SCEVPredicate *, 4> Predicates;
8908 // We handle only IV < Invariant
8909 if (!isLoopInvariant(RHS, L))
8910 return getCouldNotCompute();
8912 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
8913 bool PredicatedIV = false;
8915 if (!IV && AllowPredicates) {
8916 // Try to make this an AddRec using runtime tests, in the first X
8917 // iterations of this loop, where X is the SCEV expression found by the
8919 IV = convertSCEVToAddRecWithPredicates(LHS, L, Predicates);
8920 PredicatedIV = true;
8923 // Avoid weird loops
8924 if (!IV || IV->getLoop() != L || !IV->isAffine())
8925 return getCouldNotCompute();
8927 bool NoWrap = ControlsExit &&
8928 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
8930 const SCEV *Stride = IV->getStepRecurrence(*this);
8932 bool PositiveStride = isKnownPositive(Stride);
8934 // Avoid negative or zero stride values.
8935 if (!PositiveStride) {
8936 // We can compute the correct backedge taken count for loops with unknown
8937 // strides if we can prove that the loop is not an infinite loop with side
8938 // effects. Here's the loop structure we are trying to handle -
8944 // } while (i < end);
8946 // The backedge taken count for such loops is evaluated as -
8947 // (max(end, start + stride) - start - 1) /u stride
8949 // The additional preconditions that we need to check to prove correctness
8950 // of the above formula is as follows -
8952 // a) IV is either nuw or nsw depending upon signedness (indicated by the
8954 // b) loop is single exit with no side effects.
8957 // Precondition a) implies that if the stride is negative, this is a single
8958 // trip loop. The backedge taken count formula reduces to zero in this case.
8960 // Precondition b) implies that the unknown stride cannot be zero otherwise
8963 // The positive stride case is the same as isKnownPositive(Stride) returning
8964 // true (original behavior of the function).
8966 // We want to make sure that the stride is truly unknown as there are edge
8967 // cases where ScalarEvolution propagates no wrap flags to the
8968 // post-increment/decrement IV even though the increment/decrement operation
8969 // itself is wrapping. The computed backedge taken count may be wrong in
8970 // such cases. This is prevented by checking that the stride is not known to
8971 // be either positive or non-positive. For example, no wrap flags are
8972 // propagated to the post-increment IV of this loop with a trip count of 2 -
8975 // for(i=127; i<128; i+=129)
8978 if (PredicatedIV || !NoWrap || isKnownNonPositive(Stride) ||
8979 !loopHasNoSideEffects(L))
8980 return getCouldNotCompute();
8982 } else if (!Stride->isOne() &&
8983 doesIVOverflowOnLT(RHS, Stride, IsSigned, NoWrap))
8984 // Avoid proven overflow cases: this will ensure that the backedge taken
8985 // count will not generate any unsigned overflow. Relaxed no-overflow
8986 // conditions exploit NoWrapFlags, allowing to optimize in presence of
8987 // undefined behaviors like the case of C language.
8988 return getCouldNotCompute();
8990 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT
8991 : ICmpInst::ICMP_ULT;
8992 const SCEV *Start = IV->getStart();
8993 const SCEV *End = RHS;
8994 // If the backedge is taken at least once, then it will be taken
8995 // (End-Start)/Stride times (rounded up to a multiple of Stride), where Start
8996 // is the LHS value of the less-than comparison the first time it is evaluated
8997 // and End is the RHS.
8998 const SCEV *BECountIfBackedgeTaken =
8999 computeBECount(getMinusSCEV(End, Start), Stride, false);
9000 // If the loop entry is guarded by the result of the backedge test of the
9001 // first loop iteration, then we know the backedge will be taken at least
9002 // once and so the backedge taken count is as above. If not then we use the
9003 // expression (max(End,Start)-Start)/Stride to describe the backedge count,
9004 // as if the backedge is taken at least once max(End,Start) is End and so the
9005 // result is as above, and if not max(End,Start) is Start so we get a backedge
9007 const SCEV *BECount;
9008 if (isLoopEntryGuardedByCond(L, Cond, getMinusSCEV(Start, Stride), RHS))
9009 BECount = BECountIfBackedgeTaken;
9011 End = IsSigned ? getSMaxExpr(RHS, Start) : getUMaxExpr(RHS, Start);
9012 BECount = computeBECount(getMinusSCEV(End, Start), Stride, false);
9015 const SCEV *MaxBECount;
9016 bool MaxOrZero = false;
9017 if (isa<SCEVConstant>(BECount))
9018 MaxBECount = BECount;
9019 else if (isa<SCEVConstant>(BECountIfBackedgeTaken)) {
9020 // If we know exactly how many times the backedge will be taken if it's
9021 // taken at least once, then the backedge count will either be that or
9023 MaxBECount = BECountIfBackedgeTaken;
9026 // Calculate the maximum backedge count based on the range of values
9027 // permitted by Start, End, and Stride.
9028 APInt MinStart = IsSigned ? getSignedRange(Start).getSignedMin()
9029 : getUnsignedRange(Start).getUnsignedMin();
9031 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
9033 APInt StrideForMaxBECount;
9036 StrideForMaxBECount =
9037 IsSigned ? getSignedRange(Stride).getSignedMin()
9038 : getUnsignedRange(Stride).getUnsignedMin();
9040 // Using a stride of 1 is safe when computing max backedge taken count for
9041 // a loop with unknown stride.
9042 StrideForMaxBECount = APInt(BitWidth, 1, IsSigned);
9045 IsSigned ? APInt::getSignedMaxValue(BitWidth) - (StrideForMaxBECount - 1)
9046 : APInt::getMaxValue(BitWidth) - (StrideForMaxBECount - 1);
9048 // Although End can be a MAX expression we estimate MaxEnd considering only
9049 // the case End = RHS. This is safe because in the other case (End - Start)
9050 // is zero, leading to a zero maximum backedge taken count.
9052 IsSigned ? APIntOps::smin(getSignedRange(RHS).getSignedMax(), Limit)
9053 : APIntOps::umin(getUnsignedRange(RHS).getUnsignedMax(), Limit);
9055 MaxBECount = computeBECount(getConstant(MaxEnd - MinStart),
9056 getConstant(StrideForMaxBECount), false);
9059 if (isa<SCEVCouldNotCompute>(MaxBECount))
9060 MaxBECount = BECount;
9062 return ExitLimit(BECount, MaxBECount, MaxOrZero, Predicates);
9065 ScalarEvolution::ExitLimit
9066 ScalarEvolution::howManyGreaterThans(const SCEV *LHS, const SCEV *RHS,
9067 const Loop *L, bool IsSigned,
9068 bool ControlsExit, bool AllowPredicates) {
9069 SmallPtrSet<const SCEVPredicate *, 4> Predicates;
9070 // We handle only IV > Invariant
9071 if (!isLoopInvariant(RHS, L))
9072 return getCouldNotCompute();
9074 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
9075 if (!IV && AllowPredicates)
9076 // Try to make this an AddRec using runtime tests, in the first X
9077 // iterations of this loop, where X is the SCEV expression found by the
9079 IV = convertSCEVToAddRecWithPredicates(LHS, L, Predicates);
9081 // Avoid weird loops
9082 if (!IV || IV->getLoop() != L || !IV->isAffine())
9083 return getCouldNotCompute();
9085 bool NoWrap = ControlsExit &&
9086 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
9088 const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this));
9090 // Avoid negative or zero stride values
9091 if (!isKnownPositive(Stride))
9092 return getCouldNotCompute();
9094 // Avoid proven overflow cases: this will ensure that the backedge taken count
9095 // will not generate any unsigned overflow. Relaxed no-overflow conditions
9096 // exploit NoWrapFlags, allowing to optimize in presence of undefined
9097 // behaviors like the case of C language.
9098 if (!Stride->isOne() && doesIVOverflowOnGT(RHS, Stride, IsSigned, NoWrap))
9099 return getCouldNotCompute();
9101 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT
9102 : ICmpInst::ICMP_UGT;
9104 const SCEV *Start = IV->getStart();
9105 const SCEV *End = RHS;
9106 if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS))
9107 End = IsSigned ? getSMinExpr(RHS, Start) : getUMinExpr(RHS, Start);
9109 const SCEV *BECount = computeBECount(getMinusSCEV(Start, End), Stride, false);
9111 APInt MaxStart = IsSigned ? getSignedRange(Start).getSignedMax()
9112 : getUnsignedRange(Start).getUnsignedMax();
9114 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
9115 : getUnsignedRange(Stride).getUnsignedMin();
9117 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
9118 APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1)
9119 : APInt::getMinValue(BitWidth) + (MinStride - 1);
9121 // Although End can be a MIN expression we estimate MinEnd considering only
9122 // the case End = RHS. This is safe because in the other case (Start - End)
9123 // is zero, leading to a zero maximum backedge taken count.
9125 IsSigned ? APIntOps::smax(getSignedRange(RHS).getSignedMin(), Limit)
9126 : APIntOps::umax(getUnsignedRange(RHS).getUnsignedMin(), Limit);
9129 const SCEV *MaxBECount = getCouldNotCompute();
9130 if (isa<SCEVConstant>(BECount))
9131 MaxBECount = BECount;
9133 MaxBECount = computeBECount(getConstant(MaxStart - MinEnd),
9134 getConstant(MinStride), false);
9136 if (isa<SCEVCouldNotCompute>(MaxBECount))
9137 MaxBECount = BECount;
9139 return ExitLimit(BECount, MaxBECount, false, Predicates);
9142 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(const ConstantRange &Range,
9143 ScalarEvolution &SE) const {
9144 if (Range.isFullSet()) // Infinite loop.
9145 return SE.getCouldNotCompute();
9147 // If the start is a non-zero constant, shift the range to simplify things.
9148 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
9149 if (!SC->getValue()->isZero()) {
9150 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
9151 Operands[0] = SE.getZero(SC->getType());
9152 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
9153 getNoWrapFlags(FlagNW));
9154 if (const auto *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted))
9155 return ShiftedAddRec->getNumIterationsInRange(
9156 Range.subtract(SC->getAPInt()), SE);
9157 // This is strange and shouldn't happen.
9158 return SE.getCouldNotCompute();
9161 // The only time we can solve this is when we have all constant indices.
9162 // Otherwise, we cannot determine the overflow conditions.
9163 if (any_of(operands(), [](const SCEV *Op) { return !isa<SCEVConstant>(Op); }))
9164 return SE.getCouldNotCompute();
9166 // Okay at this point we know that all elements of the chrec are constants and
9167 // that the start element is zero.
9169 // First check to see if the range contains zero. If not, the first
9171 unsigned BitWidth = SE.getTypeSizeInBits(getType());
9172 if (!Range.contains(APInt(BitWidth, 0)))
9173 return SE.getZero(getType());
9176 // If this is an affine expression then we have this situation:
9177 // Solve {0,+,A} in Range === Ax in Range
9179 // We know that zero is in the range. If A is positive then we know that
9180 // the upper value of the range must be the first possible exit value.
9181 // If A is negative then the lower of the range is the last possible loop
9182 // value. Also note that we already checked for a full range.
9183 APInt One(BitWidth,1);
9184 APInt A = cast<SCEVConstant>(getOperand(1))->getAPInt();
9185 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
9187 // The exit value should be (End+A)/A.
9188 APInt ExitVal = (End + A).udiv(A);
9189 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
9191 // Evaluate at the exit value. If we really did fall out of the valid
9192 // range, then we computed our trip count, otherwise wrap around or other
9193 // things must have happened.
9194 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
9195 if (Range.contains(Val->getValue()))
9196 return SE.getCouldNotCompute(); // Something strange happened
9198 // Ensure that the previous value is in the range. This is a sanity check.
9199 assert(Range.contains(
9200 EvaluateConstantChrecAtConstant(this,
9201 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
9202 "Linear scev computation is off in a bad way!");
9203 return SE.getConstant(ExitValue);
9204 } else if (isQuadratic()) {
9205 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
9206 // quadratic equation to solve it. To do this, we must frame our problem in
9207 // terms of figuring out when zero is crossed, instead of when
9208 // Range.getUpper() is crossed.
9209 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
9210 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
9211 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(), FlagAnyWrap);
9213 // Next, solve the constructed addrec
9215 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE)) {
9216 const SCEVConstant *R1 = Roots->first;
9217 const SCEVConstant *R2 = Roots->second;
9218 // Pick the smallest positive root value.
9219 if (ConstantInt *CB = dyn_cast<ConstantInt>(ConstantExpr::getICmp(
9220 ICmpInst::ICMP_ULT, R1->getValue(), R2->getValue()))) {
9221 if (!CB->getZExtValue())
9222 std::swap(R1, R2); // R1 is the minimum root now.
9224 // Make sure the root is not off by one. The returned iteration should
9225 // not be in the range, but the previous one should be. When solving
9226 // for "X*X < 5", for example, we should not return a root of 2.
9227 ConstantInt *R1Val =
9228 EvaluateConstantChrecAtConstant(this, R1->getValue(), SE);
9229 if (Range.contains(R1Val->getValue())) {
9230 // The next iteration must be out of the range...
9231 ConstantInt *NextVal =
9232 ConstantInt::get(SE.getContext(), R1->getAPInt() + 1);
9234 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
9235 if (!Range.contains(R1Val->getValue()))
9236 return SE.getConstant(NextVal);
9237 return SE.getCouldNotCompute(); // Something strange happened
9240 // If R1 was not in the range, then it is a good return value. Make
9241 // sure that R1-1 WAS in the range though, just in case.
9242 ConstantInt *NextVal =
9243 ConstantInt::get(SE.getContext(), R1->getAPInt() - 1);
9244 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
9245 if (Range.contains(R1Val->getValue()))
9247 return SE.getCouldNotCompute(); // Something strange happened
9252 return SE.getCouldNotCompute();
9255 // Return true when S contains at least an undef value.
9256 static inline bool containsUndefs(const SCEV *S) {
9257 return SCEVExprContains(S, [](const SCEV *S) {
9258 if (const auto *SU = dyn_cast<SCEVUnknown>(S))
9259 return isa<UndefValue>(SU->getValue());
9260 else if (const auto *SC = dyn_cast<SCEVConstant>(S))
9261 return isa<UndefValue>(SC->getValue());
9267 // Collect all steps of SCEV expressions.
9268 struct SCEVCollectStrides {
9269 ScalarEvolution &SE;
9270 SmallVectorImpl<const SCEV *> &Strides;
9272 SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S)
9273 : SE(SE), Strides(S) {}
9275 bool follow(const SCEV *S) {
9276 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
9277 Strides.push_back(AR->getStepRecurrence(SE));
9280 bool isDone() const { return false; }
9283 // Collect all SCEVUnknown and SCEVMulExpr expressions.
9284 struct SCEVCollectTerms {
9285 SmallVectorImpl<const SCEV *> &Terms;
9287 SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T)
9290 bool follow(const SCEV *S) {
9291 if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S) ||
9292 isa<SCEVSignExtendExpr>(S)) {
9293 if (!containsUndefs(S))
9296 // Stop recursion: once we collected a term, do not walk its operands.
9303 bool isDone() const { return false; }
9306 // Check if a SCEV contains an AddRecExpr.
9307 struct SCEVHasAddRec {
9308 bool &ContainsAddRec;
9310 SCEVHasAddRec(bool &ContainsAddRec) : ContainsAddRec(ContainsAddRec) {
9311 ContainsAddRec = false;
9314 bool follow(const SCEV *S) {
9315 if (isa<SCEVAddRecExpr>(S)) {
9316 ContainsAddRec = true;
9318 // Stop recursion: once we collected a term, do not walk its operands.
9325 bool isDone() const { return false; }
9328 // Find factors that are multiplied with an expression that (possibly as a
9329 // subexpression) contains an AddRecExpr. In the expression:
9331 // 8 * (100 + %p * %q * (%a + {0, +, 1}_loop))
9333 // "%p * %q" are factors multiplied by the expression "(%a + {0, +, 1}_loop)"
9334 // that contains the AddRec {0, +, 1}_loop. %p * %q are likely to be array size
9335 // parameters as they form a product with an induction variable.
9337 // This collector expects all array size parameters to be in the same MulExpr.
9338 // It might be necessary to later add support for collecting parameters that are
9339 // spread over different nested MulExpr.
9340 struct SCEVCollectAddRecMultiplies {
9341 SmallVectorImpl<const SCEV *> &Terms;
9342 ScalarEvolution &SE;
9344 SCEVCollectAddRecMultiplies(SmallVectorImpl<const SCEV *> &T, ScalarEvolution &SE)
9345 : Terms(T), SE(SE) {}
9347 bool follow(const SCEV *S) {
9348 if (auto *Mul = dyn_cast<SCEVMulExpr>(S)) {
9349 bool HasAddRec = false;
9350 SmallVector<const SCEV *, 0> Operands;
9351 for (auto Op : Mul->operands()) {
9352 if (isa<SCEVUnknown>(Op)) {
9353 Operands.push_back(Op);
9355 bool ContainsAddRec;
9356 SCEVHasAddRec ContiansAddRec(ContainsAddRec);
9357 visitAll(Op, ContiansAddRec);
9358 HasAddRec |= ContainsAddRec;
9361 if (Operands.size() == 0)
9367 Terms.push_back(SE.getMulExpr(Operands));
9368 // Stop recursion: once we collected a term, do not walk its operands.
9375 bool isDone() const { return false; }
9379 /// Find parametric terms in this SCEVAddRecExpr. We first for parameters in
9381 /// 1) The strides of AddRec expressions.
9382 /// 2) Unknowns that are multiplied with AddRec expressions.
9383 void ScalarEvolution::collectParametricTerms(const SCEV *Expr,
9384 SmallVectorImpl<const SCEV *> &Terms) {
9385 SmallVector<const SCEV *, 4> Strides;
9386 SCEVCollectStrides StrideCollector(*this, Strides);
9387 visitAll(Expr, StrideCollector);
9390 dbgs() << "Strides:\n";
9391 for (const SCEV *S : Strides)
9392 dbgs() << *S << "\n";
9395 for (const SCEV *S : Strides) {
9396 SCEVCollectTerms TermCollector(Terms);
9397 visitAll(S, TermCollector);
9401 dbgs() << "Terms:\n";
9402 for (const SCEV *T : Terms)
9403 dbgs() << *T << "\n";
9406 SCEVCollectAddRecMultiplies MulCollector(Terms, *this);
9407 visitAll(Expr, MulCollector);
9410 static bool findArrayDimensionsRec(ScalarEvolution &SE,
9411 SmallVectorImpl<const SCEV *> &Terms,
9412 SmallVectorImpl<const SCEV *> &Sizes) {
9413 int Last = Terms.size() - 1;
9414 const SCEV *Step = Terms[Last];
9416 // End of recursion.
9418 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) {
9419 SmallVector<const SCEV *, 2> Qs;
9420 for (const SCEV *Op : M->operands())
9421 if (!isa<SCEVConstant>(Op))
9424 Step = SE.getMulExpr(Qs);
9427 Sizes.push_back(Step);
9431 for (const SCEV *&Term : Terms) {
9432 // Normalize the terms before the next call to findArrayDimensionsRec.
9434 SCEVDivision::divide(SE, Term, Step, &Q, &R);
9436 // Bail out when GCD does not evenly divide one of the terms.
9443 // Remove all SCEVConstants.
9445 remove_if(Terms, [](const SCEV *E) { return isa<SCEVConstant>(E); }),
9448 if (Terms.size() > 0)
9449 if (!findArrayDimensionsRec(SE, Terms, Sizes))
9452 Sizes.push_back(Step);
9457 // Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter.
9458 static inline bool containsParameters(SmallVectorImpl<const SCEV *> &Terms) {
9459 for (const SCEV *T : Terms)
9460 if (SCEVExprContains(T, isa<SCEVUnknown, const SCEV *>))
9465 // Return the number of product terms in S.
9466 static inline int numberOfTerms(const SCEV *S) {
9467 if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S))
9468 return Expr->getNumOperands();
9472 static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) {
9473 if (isa<SCEVConstant>(T))
9476 if (isa<SCEVUnknown>(T))
9479 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) {
9480 SmallVector<const SCEV *, 2> Factors;
9481 for (const SCEV *Op : M->operands())
9482 if (!isa<SCEVConstant>(Op))
9483 Factors.push_back(Op);
9485 return SE.getMulExpr(Factors);
9491 /// Return the size of an element read or written by Inst.
9492 const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) {
9494 if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
9495 Ty = Store->getValueOperand()->getType();
9496 else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
9497 Ty = Load->getType();
9501 Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty));
9502 return getSizeOfExpr(ETy, Ty);
9505 void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
9506 SmallVectorImpl<const SCEV *> &Sizes,
9507 const SCEV *ElementSize) const {
9508 if (Terms.size() < 1 || !ElementSize)
9511 // Early return when Terms do not contain parameters: we do not delinearize
9512 // non parametric SCEVs.
9513 if (!containsParameters(Terms))
9517 dbgs() << "Terms:\n";
9518 for (const SCEV *T : Terms)
9519 dbgs() << *T << "\n";
9522 // Remove duplicates.
9523 std::sort(Terms.begin(), Terms.end());
9524 Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end());
9526 // Put larger terms first.
9527 std::sort(Terms.begin(), Terms.end(), [](const SCEV *LHS, const SCEV *RHS) {
9528 return numberOfTerms(LHS) > numberOfTerms(RHS);
9531 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
9533 // Try to divide all terms by the element size. If term is not divisible by
9534 // element size, proceed with the original term.
9535 for (const SCEV *&Term : Terms) {
9537 SCEVDivision::divide(SE, Term, ElementSize, &Q, &R);
9542 SmallVector<const SCEV *, 4> NewTerms;
9544 // Remove constant factors.
9545 for (const SCEV *T : Terms)
9546 if (const SCEV *NewT = removeConstantFactors(SE, T))
9547 NewTerms.push_back(NewT);
9550 dbgs() << "Terms after sorting:\n";
9551 for (const SCEV *T : NewTerms)
9552 dbgs() << *T << "\n";
9555 if (NewTerms.empty() ||
9556 !findArrayDimensionsRec(SE, NewTerms, Sizes)) {
9561 // The last element to be pushed into Sizes is the size of an element.
9562 Sizes.push_back(ElementSize);
9565 dbgs() << "Sizes:\n";
9566 for (const SCEV *S : Sizes)
9567 dbgs() << *S << "\n";
9571 void ScalarEvolution::computeAccessFunctions(
9572 const SCEV *Expr, SmallVectorImpl<const SCEV *> &Subscripts,
9573 SmallVectorImpl<const SCEV *> &Sizes) {
9575 // Early exit in case this SCEV is not an affine multivariate function.
9579 if (auto *AR = dyn_cast<SCEVAddRecExpr>(Expr))
9580 if (!AR->isAffine())
9583 const SCEV *Res = Expr;
9584 int Last = Sizes.size() - 1;
9585 for (int i = Last; i >= 0; i--) {
9587 SCEVDivision::divide(*this, Res, Sizes[i], &Q, &R);
9590 dbgs() << "Res: " << *Res << "\n";
9591 dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";
9592 dbgs() << "Res divided by Sizes[i]:\n";
9593 dbgs() << "Quotient: " << *Q << "\n";
9594 dbgs() << "Remainder: " << *R << "\n";
9599 // Do not record the last subscript corresponding to the size of elements in
9603 // Bail out if the remainder is too complex.
9604 if (isa<SCEVAddRecExpr>(R)) {
9613 // Record the access function for the current subscript.
9614 Subscripts.push_back(R);
9617 // Also push in last position the remainder of the last division: it will be
9618 // the access function of the innermost dimension.
9619 Subscripts.push_back(Res);
9621 std::reverse(Subscripts.begin(), Subscripts.end());
9624 dbgs() << "Subscripts:\n";
9625 for (const SCEV *S : Subscripts)
9626 dbgs() << *S << "\n";
9630 /// Splits the SCEV into two vectors of SCEVs representing the subscripts and
9631 /// sizes of an array access. Returns the remainder of the delinearization that
9632 /// is the offset start of the array. The SCEV->delinearize algorithm computes
9633 /// the multiples of SCEV coefficients: that is a pattern matching of sub
9634 /// expressions in the stride and base of a SCEV corresponding to the
9635 /// computation of a GCD (greatest common divisor) of base and stride. When
9636 /// SCEV->delinearize fails, it returns the SCEV unchanged.
9638 /// For example: when analyzing the memory access A[i][j][k] in this loop nest
9640 /// void foo(long n, long m, long o, double A[n][m][o]) {
9642 /// for (long i = 0; i < n; i++)
9643 /// for (long j = 0; j < m; j++)
9644 /// for (long k = 0; k < o; k++)
9645 /// A[i][j][k] = 1.0;
9648 /// the delinearization input is the following AddRec SCEV:
9650 /// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k>
9652 /// From this SCEV, we are able to say that the base offset of the access is %A
9653 /// because it appears as an offset that does not divide any of the strides in
9656 /// CHECK: Base offset: %A
9658 /// and then SCEV->delinearize determines the size of some of the dimensions of
9659 /// the array as these are the multiples by which the strides are happening:
9661 /// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes.
9663 /// Note that the outermost dimension remains of UnknownSize because there are
9664 /// no strides that would help identifying the size of the last dimension: when
9665 /// the array has been statically allocated, one could compute the size of that
9666 /// dimension by dividing the overall size of the array by the size of the known
9667 /// dimensions: %m * %o * 8.
9669 /// Finally delinearize provides the access functions for the array reference
9670 /// that does correspond to A[i][j][k] of the above C testcase:
9672 /// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>]
9674 /// The testcases are checking the output of a function pass:
9675 /// DelinearizationPass that walks through all loads and stores of a function
9676 /// asking for the SCEV of the memory access with respect to all enclosing
9677 /// loops, calling SCEV->delinearize on that and printing the results.
9679 void ScalarEvolution::delinearize(const SCEV *Expr,
9680 SmallVectorImpl<const SCEV *> &Subscripts,
9681 SmallVectorImpl<const SCEV *> &Sizes,
9682 const SCEV *ElementSize) {
9683 // First step: collect parametric terms.
9684 SmallVector<const SCEV *, 4> Terms;
9685 collectParametricTerms(Expr, Terms);
9690 // Second step: find subscript sizes.
9691 findArrayDimensions(Terms, Sizes, ElementSize);
9696 // Third step: compute the access functions for each subscript.
9697 computeAccessFunctions(Expr, Subscripts, Sizes);
9699 if (Subscripts.empty())
9703 dbgs() << "succeeded to delinearize " << *Expr << "\n";
9704 dbgs() << "ArrayDecl[UnknownSize]";
9705 for (const SCEV *S : Sizes)
9706 dbgs() << "[" << *S << "]";
9708 dbgs() << "\nArrayRef";
9709 for (const SCEV *S : Subscripts)
9710 dbgs() << "[" << *S << "]";
9715 //===----------------------------------------------------------------------===//
9716 // SCEVCallbackVH Class Implementation
9717 //===----------------------------------------------------------------------===//
9719 void ScalarEvolution::SCEVCallbackVH::deleted() {
9720 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
9721 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
9722 SE->ConstantEvolutionLoopExitValue.erase(PN);
9723 SE->eraseValueFromMap(getValPtr());
9724 // this now dangles!
9727 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
9728 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
9730 // Forget all the expressions associated with users of the old value,
9731 // so that future queries will recompute the expressions using the new
9733 Value *Old = getValPtr();
9734 SmallVector<User *, 16> Worklist(Old->user_begin(), Old->user_end());
9735 SmallPtrSet<User *, 8> Visited;
9736 while (!Worklist.empty()) {
9737 User *U = Worklist.pop_back_val();
9738 // Deleting the Old value will cause this to dangle. Postpone
9739 // that until everything else is done.
9742 if (!Visited.insert(U).second)
9744 if (PHINode *PN = dyn_cast<PHINode>(U))
9745 SE->ConstantEvolutionLoopExitValue.erase(PN);
9746 SE->eraseValueFromMap(U);
9747 Worklist.insert(Worklist.end(), U->user_begin(), U->user_end());
9749 // Delete the Old value.
9750 if (PHINode *PN = dyn_cast<PHINode>(Old))
9751 SE->ConstantEvolutionLoopExitValue.erase(PN);
9752 SE->eraseValueFromMap(Old);
9753 // this now dangles!
9756 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
9757 : CallbackVH(V), SE(se) {}
9759 //===----------------------------------------------------------------------===//
9760 // ScalarEvolution Class Implementation
9761 //===----------------------------------------------------------------------===//
9763 ScalarEvolution::ScalarEvolution(Function &F, TargetLibraryInfo &TLI,
9764 AssumptionCache &AC, DominatorTree &DT,
9766 : F(F), TLI(TLI), AC(AC), DT(DT), LI(LI),
9767 CouldNotCompute(new SCEVCouldNotCompute()),
9768 WalkingBEDominatingConds(false), ProvingSplitPredicate(false),
9769 ValuesAtScopes(64), LoopDispositions(64), BlockDispositions(64),
9770 FirstUnknown(nullptr) {
9772 // To use guards for proving predicates, we need to scan every instruction in
9773 // relevant basic blocks, and not just terminators. Doing this is a waste of
9774 // time if the IR does not actually contain any calls to
9775 // @llvm.experimental.guard, so do a quick check and remember this beforehand.
9777 // This pessimizes the case where a pass that preserves ScalarEvolution wants
9778 // to _add_ guards to the module when there weren't any before, and wants
9779 // ScalarEvolution to optimize based on those guards. For now we prefer to be
9780 // efficient in lieu of being smart in that rather obscure case.
9782 auto *GuardDecl = F.getParent()->getFunction(
9783 Intrinsic::getName(Intrinsic::experimental_guard));
9784 HasGuards = GuardDecl && !GuardDecl->use_empty();
9787 ScalarEvolution::ScalarEvolution(ScalarEvolution &&Arg)
9788 : F(Arg.F), HasGuards(Arg.HasGuards), TLI(Arg.TLI), AC(Arg.AC), DT(Arg.DT),
9789 LI(Arg.LI), CouldNotCompute(std::move(Arg.CouldNotCompute)),
9790 ValueExprMap(std::move(Arg.ValueExprMap)),
9791 PendingLoopPredicates(std::move(Arg.PendingLoopPredicates)),
9792 WalkingBEDominatingConds(false), ProvingSplitPredicate(false),
9793 MinTrailingZerosCache(std::move(Arg.MinTrailingZerosCache)),
9794 BackedgeTakenCounts(std::move(Arg.BackedgeTakenCounts)),
9795 PredicatedBackedgeTakenCounts(
9796 std::move(Arg.PredicatedBackedgeTakenCounts)),
9797 ConstantEvolutionLoopExitValue(
9798 std::move(Arg.ConstantEvolutionLoopExitValue)),
9799 ValuesAtScopes(std::move(Arg.ValuesAtScopes)),
9800 LoopDispositions(std::move(Arg.LoopDispositions)),
9801 LoopPropertiesCache(std::move(Arg.LoopPropertiesCache)),
9802 BlockDispositions(std::move(Arg.BlockDispositions)),
9803 UnsignedRanges(std::move(Arg.UnsignedRanges)),
9804 SignedRanges(std::move(Arg.SignedRanges)),
9805 UniqueSCEVs(std::move(Arg.UniqueSCEVs)),
9806 UniquePreds(std::move(Arg.UniquePreds)),
9807 SCEVAllocator(std::move(Arg.SCEVAllocator)),
9808 FirstUnknown(Arg.FirstUnknown) {
9809 Arg.FirstUnknown = nullptr;
9812 ScalarEvolution::~ScalarEvolution() {
9813 // Iterate through all the SCEVUnknown instances and call their
9814 // destructors, so that they release their references to their values.
9815 for (SCEVUnknown *U = FirstUnknown; U;) {
9816 SCEVUnknown *Tmp = U;
9818 Tmp->~SCEVUnknown();
9820 FirstUnknown = nullptr;
9822 ExprValueMap.clear();
9823 ValueExprMap.clear();
9826 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
9827 // that a loop had multiple computable exits.
9828 for (auto &BTCI : BackedgeTakenCounts)
9829 BTCI.second.clear();
9830 for (auto &BTCI : PredicatedBackedgeTakenCounts)
9831 BTCI.second.clear();
9833 assert(PendingLoopPredicates.empty() && "isImpliedCond garbage");
9834 assert(!WalkingBEDominatingConds && "isLoopBackedgeGuardedByCond garbage!");
9835 assert(!ProvingSplitPredicate && "ProvingSplitPredicate garbage!");
9838 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
9839 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
9842 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
9844 // Print all inner loops first
9846 PrintLoopInfo(OS, SE, I);
9849 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9852 SmallVector<BasicBlock *, 8> ExitBlocks;
9853 L->getExitBlocks(ExitBlocks);
9854 if (ExitBlocks.size() != 1)
9855 OS << "<multiple exits> ";
9857 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
9858 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
9860 OS << "Unpredictable backedge-taken count. ";
9865 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9868 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
9869 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
9870 if (SE->isBackedgeTakenCountMaxOrZero(L))
9871 OS << ", actual taken count either this or zero.";
9873 OS << "Unpredictable max backedge-taken count. ";
9878 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9881 SCEVUnionPredicate Pred;
9882 auto PBT = SE->getPredicatedBackedgeTakenCount(L, Pred);
9883 if (!isa<SCEVCouldNotCompute>(PBT)) {
9884 OS << "Predicated backedge-taken count is " << *PBT << "\n";
9885 OS << " Predicates:\n";
9888 OS << "Unpredictable predicated backedge-taken count. ";
9892 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
9894 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9896 OS << "Trip multiple is " << SE->getSmallConstantTripMultiple(L) << "\n";
9900 static StringRef loopDispositionToStr(ScalarEvolution::LoopDisposition LD) {
9902 case ScalarEvolution::LoopVariant:
9904 case ScalarEvolution::LoopInvariant:
9906 case ScalarEvolution::LoopComputable:
9907 return "Computable";
9909 llvm_unreachable("Unknown ScalarEvolution::LoopDisposition kind!");
9912 void ScalarEvolution::print(raw_ostream &OS) const {
9913 // ScalarEvolution's implementation of the print method is to print
9914 // out SCEV values of all instructions that are interesting. Doing
9915 // this potentially causes it to create new SCEV objects though,
9916 // which technically conflicts with the const qualifier. This isn't
9917 // observable from outside the class though, so casting away the
9918 // const isn't dangerous.
9919 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
9921 OS << "Classifying expressions for: ";
9922 F.printAsOperand(OS, /*PrintType=*/false);
9924 for (Instruction &I : instructions(F))
9925 if (isSCEVable(I.getType()) && !isa<CmpInst>(I)) {
9928 const SCEV *SV = SE.getSCEV(&I);
9930 if (!isa<SCEVCouldNotCompute>(SV)) {
9932 SE.getUnsignedRange(SV).print(OS);
9934 SE.getSignedRange(SV).print(OS);
9937 const Loop *L = LI.getLoopFor(I.getParent());
9939 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
9943 if (!isa<SCEVCouldNotCompute>(AtUse)) {
9945 SE.getUnsignedRange(AtUse).print(OS);
9947 SE.getSignedRange(AtUse).print(OS);
9952 OS << "\t\t" "Exits: ";
9953 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
9954 if (!SE.isLoopInvariant(ExitValue, L)) {
9955 OS << "<<Unknown>>";
9961 for (auto *Iter = L; Iter; Iter = Iter->getParentLoop()) {
9963 OS << "\t\t" "LoopDispositions: { ";
9969 Iter->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9970 OS << ": " << loopDispositionToStr(SE.getLoopDisposition(SV, Iter));
9973 for (auto *InnerL : depth_first(L)) {
9977 OS << "\t\t" "LoopDispositions: { ";
9983 InnerL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9984 OS << ": " << loopDispositionToStr(SE.getLoopDisposition(SV, InnerL));
9993 OS << "Determining loop execution counts for: ";
9994 F.printAsOperand(OS, /*PrintType=*/false);
9997 PrintLoopInfo(OS, &SE, I);
10000 ScalarEvolution::LoopDisposition
10001 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
10002 auto &Values = LoopDispositions[S];
10003 for (auto &V : Values) {
10004 if (V.getPointer() == L)
10007 Values.emplace_back(L, LoopVariant);
10008 LoopDisposition D = computeLoopDisposition(S, L);
10009 auto &Values2 = LoopDispositions[S];
10010 for (auto &V : make_range(Values2.rbegin(), Values2.rend())) {
10011 if (V.getPointer() == L) {
10019 ScalarEvolution::LoopDisposition
10020 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
10021 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
10023 return LoopInvariant;
10027 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
10028 case scAddRecExpr: {
10029 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
10031 // If L is the addrec's loop, it's computable.
10032 if (AR->getLoop() == L)
10033 return LoopComputable;
10035 // Add recurrences are never invariant in the function-body (null loop).
10037 return LoopVariant;
10039 // This recurrence is variant w.r.t. L if L contains AR's loop.
10040 if (L->contains(AR->getLoop()))
10041 return LoopVariant;
10043 // This recurrence is invariant w.r.t. L if AR's loop contains L.
10044 if (AR->getLoop()->contains(L))
10045 return LoopInvariant;
10047 // This recurrence is variant w.r.t. L if any of its operands
10049 for (auto *Op : AR->operands())
10050 if (!isLoopInvariant(Op, L))
10051 return LoopVariant;
10053 // Otherwise it's loop-invariant.
10054 return LoopInvariant;
10060 bool HasVarying = false;
10061 for (auto *Op : cast<SCEVNAryExpr>(S)->operands()) {
10062 LoopDisposition D = getLoopDisposition(Op, L);
10063 if (D == LoopVariant)
10064 return LoopVariant;
10065 if (D == LoopComputable)
10068 return HasVarying ? LoopComputable : LoopInvariant;
10071 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
10072 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
10073 if (LD == LoopVariant)
10074 return LoopVariant;
10075 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
10076 if (RD == LoopVariant)
10077 return LoopVariant;
10078 return (LD == LoopInvariant && RD == LoopInvariant) ?
10079 LoopInvariant : LoopComputable;
10082 // All non-instruction values are loop invariant. All instructions are loop
10083 // invariant if they are not contained in the specified loop.
10084 // Instructions are never considered invariant in the function body
10085 // (null loop) because they are defined within the "loop".
10086 if (auto *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
10087 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
10088 return LoopInvariant;
10089 case scCouldNotCompute:
10090 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
10092 llvm_unreachable("Unknown SCEV kind!");
10095 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
10096 return getLoopDisposition(S, L) == LoopInvariant;
10099 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
10100 return getLoopDisposition(S, L) == LoopComputable;
10103 ScalarEvolution::BlockDisposition
10104 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
10105 auto &Values = BlockDispositions[S];
10106 for (auto &V : Values) {
10107 if (V.getPointer() == BB)
10110 Values.emplace_back(BB, DoesNotDominateBlock);
10111 BlockDisposition D = computeBlockDisposition(S, BB);
10112 auto &Values2 = BlockDispositions[S];
10113 for (auto &V : make_range(Values2.rbegin(), Values2.rend())) {
10114 if (V.getPointer() == BB) {
10122 ScalarEvolution::BlockDisposition
10123 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
10124 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
10126 return ProperlyDominatesBlock;
10130 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
10131 case scAddRecExpr: {
10132 // This uses a "dominates" query instead of "properly dominates" query
10133 // to test for proper dominance too, because the instruction which
10134 // produces the addrec's value is a PHI, and a PHI effectively properly
10135 // dominates its entire containing block.
10136 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
10137 if (!DT.dominates(AR->getLoop()->getHeader(), BB))
10138 return DoesNotDominateBlock;
10140 // Fall through into SCEVNAryExpr handling.
10147 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
10148 bool Proper = true;
10149 for (const SCEV *NAryOp : NAry->operands()) {
10150 BlockDisposition D = getBlockDisposition(NAryOp, BB);
10151 if (D == DoesNotDominateBlock)
10152 return DoesNotDominateBlock;
10153 if (D == DominatesBlock)
10156 return Proper ? ProperlyDominatesBlock : DominatesBlock;
10159 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
10160 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
10161 BlockDisposition LD = getBlockDisposition(LHS, BB);
10162 if (LD == DoesNotDominateBlock)
10163 return DoesNotDominateBlock;
10164 BlockDisposition RD = getBlockDisposition(RHS, BB);
10165 if (RD == DoesNotDominateBlock)
10166 return DoesNotDominateBlock;
10167 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
10168 ProperlyDominatesBlock : DominatesBlock;
10171 if (Instruction *I =
10172 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
10173 if (I->getParent() == BB)
10174 return DominatesBlock;
10175 if (DT.properlyDominates(I->getParent(), BB))
10176 return ProperlyDominatesBlock;
10177 return DoesNotDominateBlock;
10179 return ProperlyDominatesBlock;
10180 case scCouldNotCompute:
10181 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
10183 llvm_unreachable("Unknown SCEV kind!");
10186 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
10187 return getBlockDisposition(S, BB) >= DominatesBlock;
10190 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
10191 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
10194 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
10195 return SCEVExprContains(S, [&](const SCEV *Expr) { return Expr == Op; });
10198 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
10199 ValuesAtScopes.erase(S);
10200 LoopDispositions.erase(S);
10201 BlockDispositions.erase(S);
10202 UnsignedRanges.erase(S);
10203 SignedRanges.erase(S);
10204 ExprValueMap.erase(S);
10205 HasRecMap.erase(S);
10206 MinTrailingZerosCache.erase(S);
10208 auto RemoveSCEVFromBackedgeMap =
10209 [S, this](DenseMap<const Loop *, BackedgeTakenInfo> &Map) {
10210 for (auto I = Map.begin(), E = Map.end(); I != E;) {
10211 BackedgeTakenInfo &BEInfo = I->second;
10212 if (BEInfo.hasOperand(S, this)) {
10220 RemoveSCEVFromBackedgeMap(BackedgeTakenCounts);
10221 RemoveSCEVFromBackedgeMap(PredicatedBackedgeTakenCounts);
10224 typedef DenseMap<const Loop *, std::string> VerifyMap;
10226 /// replaceSubString - Replaces all occurrences of From in Str with To.
10227 static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
10229 while ((Pos = Str.find(From, Pos)) != std::string::npos) {
10230 Str.replace(Pos, From.size(), To.data(), To.size());
10235 /// getLoopBackedgeTakenCounts - Helper method for verifyAnalysis.
10237 getLoopBackedgeTakenCounts(Loop *L, VerifyMap &Map, ScalarEvolution &SE) {
10238 std::string &S = Map[L];
10240 raw_string_ostream OS(S);
10241 SE.getBackedgeTakenCount(L)->print(OS);
10243 // false and 0 are semantically equivalent. This can happen in dead loops.
10244 replaceSubString(OS.str(), "false", "0");
10245 // Remove wrap flags, their use in SCEV is highly fragile.
10246 // FIXME: Remove this when SCEV gets smarter about them.
10247 replaceSubString(OS.str(), "<nw>", "");
10248 replaceSubString(OS.str(), "<nsw>", "");
10249 replaceSubString(OS.str(), "<nuw>", "");
10252 for (auto *R : reverse(*L))
10253 getLoopBackedgeTakenCounts(R, Map, SE); // recurse.
10256 void ScalarEvolution::verify() const {
10257 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
10259 // Gather stringified backedge taken counts for all loops using SCEV's caches.
10260 // FIXME: It would be much better to store actual values instead of strings,
10261 // but SCEV pointers will change if we drop the caches.
10262 VerifyMap BackedgeDumpsOld, BackedgeDumpsNew;
10263 for (LoopInfo::reverse_iterator I = LI.rbegin(), E = LI.rend(); I != E; ++I)
10264 getLoopBackedgeTakenCounts(*I, BackedgeDumpsOld, SE);
10266 // Gather stringified backedge taken counts for all loops using a fresh
10267 // ScalarEvolution object.
10268 ScalarEvolution SE2(F, TLI, AC, DT, LI);
10269 for (LoopInfo::reverse_iterator I = LI.rbegin(), E = LI.rend(); I != E; ++I)
10270 getLoopBackedgeTakenCounts(*I, BackedgeDumpsNew, SE2);
10272 // Now compare whether they're the same with and without caches. This allows
10273 // verifying that no pass changed the cache.
10274 assert(BackedgeDumpsOld.size() == BackedgeDumpsNew.size() &&
10275 "New loops suddenly appeared!");
10277 for (VerifyMap::iterator OldI = BackedgeDumpsOld.begin(),
10278 OldE = BackedgeDumpsOld.end(),
10279 NewI = BackedgeDumpsNew.begin();
10280 OldI != OldE; ++OldI, ++NewI) {
10281 assert(OldI->first == NewI->first && "Loop order changed!");
10283 // Compare the stringified SCEVs. We don't care if undef backedgetaken count
10285 // FIXME: We currently ignore SCEV changes from/to CouldNotCompute. This
10286 // means that a pass is buggy or SCEV has to learn a new pattern but is
10287 // usually not harmful.
10288 if (OldI->second != NewI->second &&
10289 OldI->second.find("undef") == std::string::npos &&
10290 NewI->second.find("undef") == std::string::npos &&
10291 OldI->second != "***COULDNOTCOMPUTE***" &&
10292 NewI->second != "***COULDNOTCOMPUTE***") {
10293 dbgs() << "SCEVValidator: SCEV for loop '"
10294 << OldI->first->getHeader()->getName()
10295 << "' changed from '" << OldI->second
10296 << "' to '" << NewI->second << "'!\n";
10301 // TODO: Verify more things.
10304 bool ScalarEvolution::invalidate(
10305 Function &F, const PreservedAnalyses &PA,
10306 FunctionAnalysisManager::Invalidator &Inv) {
10307 // Invalidate the ScalarEvolution object whenever it isn't preserved or one
10308 // of its dependencies is invalidated.
10309 auto PAC = PA.getChecker<ScalarEvolutionAnalysis>();
10310 return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) ||
10311 Inv.invalidate<AssumptionAnalysis>(F, PA) ||
10312 Inv.invalidate<DominatorTreeAnalysis>(F, PA) ||
10313 Inv.invalidate<LoopAnalysis>(F, PA);
10316 AnalysisKey ScalarEvolutionAnalysis::Key;
10318 ScalarEvolution ScalarEvolutionAnalysis::run(Function &F,
10319 FunctionAnalysisManager &AM) {
10320 return ScalarEvolution(F, AM.getResult<TargetLibraryAnalysis>(F),
10321 AM.getResult<AssumptionAnalysis>(F),
10322 AM.getResult<DominatorTreeAnalysis>(F),
10323 AM.getResult<LoopAnalysis>(F));
10327 ScalarEvolutionPrinterPass::run(Function &F, FunctionAnalysisManager &AM) {
10328 AM.getResult<ScalarEvolutionAnalysis>(F).print(OS);
10329 return PreservedAnalyses::all();
10332 INITIALIZE_PASS_BEGIN(ScalarEvolutionWrapperPass, "scalar-evolution",
10333 "Scalar Evolution Analysis", false, true)
10334 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
10335 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
10336 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
10337 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
10338 INITIALIZE_PASS_END(ScalarEvolutionWrapperPass, "scalar-evolution",
10339 "Scalar Evolution Analysis", false, true)
10340 char ScalarEvolutionWrapperPass::ID = 0;
10342 ScalarEvolutionWrapperPass::ScalarEvolutionWrapperPass() : FunctionPass(ID) {
10343 initializeScalarEvolutionWrapperPassPass(*PassRegistry::getPassRegistry());
10346 bool ScalarEvolutionWrapperPass::runOnFunction(Function &F) {
10347 SE.reset(new ScalarEvolution(
10348 F, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
10349 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
10350 getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
10351 getAnalysis<LoopInfoWrapperPass>().getLoopInfo()));
10355 void ScalarEvolutionWrapperPass::releaseMemory() { SE.reset(); }
10357 void ScalarEvolutionWrapperPass::print(raw_ostream &OS, const Module *) const {
10361 void ScalarEvolutionWrapperPass::verifyAnalysis() const {
10368 void ScalarEvolutionWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
10369 AU.setPreservesAll();
10370 AU.addRequiredTransitive<AssumptionCacheTracker>();
10371 AU.addRequiredTransitive<LoopInfoWrapperPass>();
10372 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
10373 AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>();
10376 const SCEVPredicate *
10377 ScalarEvolution::getEqualPredicate(const SCEVUnknown *LHS,
10378 const SCEVConstant *RHS) {
10379 FoldingSetNodeID ID;
10380 // Unique this node based on the arguments
10381 ID.AddInteger(SCEVPredicate::P_Equal);
10382 ID.AddPointer(LHS);
10383 ID.AddPointer(RHS);
10384 void *IP = nullptr;
10385 if (const auto *S = UniquePreds.FindNodeOrInsertPos(ID, IP))
10387 SCEVEqualPredicate *Eq = new (SCEVAllocator)
10388 SCEVEqualPredicate(ID.Intern(SCEVAllocator), LHS, RHS);
10389 UniquePreds.InsertNode(Eq, IP);
10393 const SCEVPredicate *ScalarEvolution::getWrapPredicate(
10394 const SCEVAddRecExpr *AR,
10395 SCEVWrapPredicate::IncrementWrapFlags AddedFlags) {
10396 FoldingSetNodeID ID;
10397 // Unique this node based on the arguments
10398 ID.AddInteger(SCEVPredicate::P_Wrap);
10400 ID.AddInteger(AddedFlags);
10401 void *IP = nullptr;
10402 if (const auto *S = UniquePreds.FindNodeOrInsertPos(ID, IP))
10404 auto *OF = new (SCEVAllocator)
10405 SCEVWrapPredicate(ID.Intern(SCEVAllocator), AR, AddedFlags);
10406 UniquePreds.InsertNode(OF, IP);
10412 class SCEVPredicateRewriter : public SCEVRewriteVisitor<SCEVPredicateRewriter> {
10414 /// Rewrites \p S in the context of a loop L and the SCEV predication
10415 /// infrastructure.
10417 /// If \p Pred is non-null, the SCEV expression is rewritten to respect the
10418 /// equivalences present in \p Pred.
10420 /// If \p NewPreds is non-null, rewrite is free to add further predicates to
10421 /// \p NewPreds such that the result will be an AddRecExpr.
10422 static const SCEV *rewrite(const SCEV *S, const Loop *L, ScalarEvolution &SE,
10423 SmallPtrSetImpl<const SCEVPredicate *> *NewPreds,
10424 SCEVUnionPredicate *Pred) {
10425 SCEVPredicateRewriter Rewriter(L, SE, NewPreds, Pred);
10426 return Rewriter.visit(S);
10429 SCEVPredicateRewriter(const Loop *L, ScalarEvolution &SE,
10430 SmallPtrSetImpl<const SCEVPredicate *> *NewPreds,
10431 SCEVUnionPredicate *Pred)
10432 : SCEVRewriteVisitor(SE), NewPreds(NewPreds), Pred(Pred), L(L) {}
10434 const SCEV *visitUnknown(const SCEVUnknown *Expr) {
10436 auto ExprPreds = Pred->getPredicatesForExpr(Expr);
10437 for (auto *Pred : ExprPreds)
10438 if (const auto *IPred = dyn_cast<SCEVEqualPredicate>(Pred))
10439 if (IPred->getLHS() == Expr)
10440 return IPred->getRHS();
10446 const SCEV *visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) {
10447 const SCEV *Operand = visit(Expr->getOperand());
10448 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Operand);
10449 if (AR && AR->getLoop() == L && AR->isAffine()) {
10450 // This couldn't be folded because the operand didn't have the nuw
10451 // flag. Add the nusw flag as an assumption that we could make.
10452 const SCEV *Step = AR->getStepRecurrence(SE);
10453 Type *Ty = Expr->getType();
10454 if (addOverflowAssumption(AR, SCEVWrapPredicate::IncrementNUSW))
10455 return SE.getAddRecExpr(SE.getZeroExtendExpr(AR->getStart(), Ty),
10456 SE.getSignExtendExpr(Step, Ty), L,
10457 AR->getNoWrapFlags());
10459 return SE.getZeroExtendExpr(Operand, Expr->getType());
10462 const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *Expr) {
10463 const SCEV *Operand = visit(Expr->getOperand());
10464 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Operand);
10465 if (AR && AR->getLoop() == L && AR->isAffine()) {
10466 // This couldn't be folded because the operand didn't have the nsw
10467 // flag. Add the nssw flag as an assumption that we could make.
10468 const SCEV *Step = AR->getStepRecurrence(SE);
10469 Type *Ty = Expr->getType();
10470 if (addOverflowAssumption(AR, SCEVWrapPredicate::IncrementNSSW))
10471 return SE.getAddRecExpr(SE.getSignExtendExpr(AR->getStart(), Ty),
10472 SE.getSignExtendExpr(Step, Ty), L,
10473 AR->getNoWrapFlags());
10475 return SE.getSignExtendExpr(Operand, Expr->getType());
10479 bool addOverflowAssumption(const SCEVAddRecExpr *AR,
10480 SCEVWrapPredicate::IncrementWrapFlags AddedFlags) {
10481 auto *A = SE.getWrapPredicate(AR, AddedFlags);
10483 // Check if we've already made this assumption.
10484 return Pred && Pred->implies(A);
10486 NewPreds->insert(A);
10490 SmallPtrSetImpl<const SCEVPredicate *> *NewPreds;
10491 SCEVUnionPredicate *Pred;
10494 } // end anonymous namespace
10496 const SCEV *ScalarEvolution::rewriteUsingPredicate(const SCEV *S, const Loop *L,
10497 SCEVUnionPredicate &Preds) {
10498 return SCEVPredicateRewriter::rewrite(S, L, *this, nullptr, &Preds);
10501 const SCEVAddRecExpr *ScalarEvolution::convertSCEVToAddRecWithPredicates(
10502 const SCEV *S, const Loop *L,
10503 SmallPtrSetImpl<const SCEVPredicate *> &Preds) {
10505 SmallPtrSet<const SCEVPredicate *, 4> TransformPreds;
10506 S = SCEVPredicateRewriter::rewrite(S, L, *this, &TransformPreds, nullptr);
10507 auto *AddRec = dyn_cast<SCEVAddRecExpr>(S);
10512 // Since the transformation was successful, we can now transfer the SCEV
10514 for (auto *P : TransformPreds)
10520 /// SCEV predicates
10521 SCEVPredicate::SCEVPredicate(const FoldingSetNodeIDRef ID,
10522 SCEVPredicateKind Kind)
10523 : FastID(ID), Kind(Kind) {}
10525 SCEVEqualPredicate::SCEVEqualPredicate(const FoldingSetNodeIDRef ID,
10526 const SCEVUnknown *LHS,
10527 const SCEVConstant *RHS)
10528 : SCEVPredicate(ID, P_Equal), LHS(LHS), RHS(RHS) {}
10530 bool SCEVEqualPredicate::implies(const SCEVPredicate *N) const {
10531 const auto *Op = dyn_cast<SCEVEqualPredicate>(N);
10536 return Op->LHS == LHS && Op->RHS == RHS;
10539 bool SCEVEqualPredicate::isAlwaysTrue() const { return false; }
10541 const SCEV *SCEVEqualPredicate::getExpr() const { return LHS; }
10543 void SCEVEqualPredicate::print(raw_ostream &OS, unsigned Depth) const {
10544 OS.indent(Depth) << "Equal predicate: " << *LHS << " == " << *RHS << "\n";
10547 SCEVWrapPredicate::SCEVWrapPredicate(const FoldingSetNodeIDRef ID,
10548 const SCEVAddRecExpr *AR,
10549 IncrementWrapFlags Flags)
10550 : SCEVPredicate(ID, P_Wrap), AR(AR), Flags(Flags) {}
10552 const SCEV *SCEVWrapPredicate::getExpr() const { return AR; }
10554 bool SCEVWrapPredicate::implies(const SCEVPredicate *N) const {
10555 const auto *Op = dyn_cast<SCEVWrapPredicate>(N);
10557 return Op && Op->AR == AR && setFlags(Flags, Op->Flags) == Flags;
10560 bool SCEVWrapPredicate::isAlwaysTrue() const {
10561 SCEV::NoWrapFlags ScevFlags = AR->getNoWrapFlags();
10562 IncrementWrapFlags IFlags = Flags;
10564 if (ScalarEvolution::setFlags(ScevFlags, SCEV::FlagNSW) == ScevFlags)
10565 IFlags = clearFlags(IFlags, IncrementNSSW);
10567 return IFlags == IncrementAnyWrap;
10570 void SCEVWrapPredicate::print(raw_ostream &OS, unsigned Depth) const {
10571 OS.indent(Depth) << *getExpr() << " Added Flags: ";
10572 if (SCEVWrapPredicate::IncrementNUSW & getFlags())
10574 if (SCEVWrapPredicate::IncrementNSSW & getFlags())
10579 SCEVWrapPredicate::IncrementWrapFlags
10580 SCEVWrapPredicate::getImpliedFlags(const SCEVAddRecExpr *AR,
10581 ScalarEvolution &SE) {
10582 IncrementWrapFlags ImpliedFlags = IncrementAnyWrap;
10583 SCEV::NoWrapFlags StaticFlags = AR->getNoWrapFlags();
10585 // We can safely transfer the NSW flag as NSSW.
10586 if (ScalarEvolution::setFlags(StaticFlags, SCEV::FlagNSW) == StaticFlags)
10587 ImpliedFlags = IncrementNSSW;
10589 if (ScalarEvolution::setFlags(StaticFlags, SCEV::FlagNUW) == StaticFlags) {
10590 // If the increment is positive, the SCEV NUW flag will also imply the
10591 // WrapPredicate NUSW flag.
10592 if (const auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(SE)))
10593 if (Step->getValue()->getValue().isNonNegative())
10594 ImpliedFlags = setFlags(ImpliedFlags, IncrementNUSW);
10597 return ImpliedFlags;
10600 /// Union predicates don't get cached so create a dummy set ID for it.
10601 SCEVUnionPredicate::SCEVUnionPredicate()
10602 : SCEVPredicate(FoldingSetNodeIDRef(nullptr, 0), P_Union) {}
10604 bool SCEVUnionPredicate::isAlwaysTrue() const {
10605 return all_of(Preds,
10606 [](const SCEVPredicate *I) { return I->isAlwaysTrue(); });
10609 ArrayRef<const SCEVPredicate *>
10610 SCEVUnionPredicate::getPredicatesForExpr(const SCEV *Expr) {
10611 auto I = SCEVToPreds.find(Expr);
10612 if (I == SCEVToPreds.end())
10613 return ArrayRef<const SCEVPredicate *>();
10617 bool SCEVUnionPredicate::implies(const SCEVPredicate *N) const {
10618 if (const auto *Set = dyn_cast<SCEVUnionPredicate>(N))
10619 return all_of(Set->Preds,
10620 [this](const SCEVPredicate *I) { return this->implies(I); });
10622 auto ScevPredsIt = SCEVToPreds.find(N->getExpr());
10623 if (ScevPredsIt == SCEVToPreds.end())
10625 auto &SCEVPreds = ScevPredsIt->second;
10627 return any_of(SCEVPreds,
10628 [N](const SCEVPredicate *I) { return I->implies(N); });
10631 const SCEV *SCEVUnionPredicate::getExpr() const { return nullptr; }
10633 void SCEVUnionPredicate::print(raw_ostream &OS, unsigned Depth) const {
10634 for (auto Pred : Preds)
10635 Pred->print(OS, Depth);
10638 void SCEVUnionPredicate::add(const SCEVPredicate *N) {
10639 if (const auto *Set = dyn_cast<SCEVUnionPredicate>(N)) {
10640 for (auto Pred : Set->Preds)
10648 const SCEV *Key = N->getExpr();
10649 assert(Key && "Only SCEVUnionPredicate doesn't have an "
10650 " associated expression!");
10652 SCEVToPreds[Key].push_back(N);
10653 Preds.push_back(N);
10656 PredicatedScalarEvolution::PredicatedScalarEvolution(ScalarEvolution &SE,
10658 : SE(SE), L(L), Generation(0), BackedgeCount(nullptr) {}
10660 const SCEV *PredicatedScalarEvolution::getSCEV(Value *V) {
10661 const SCEV *Expr = SE.getSCEV(V);
10662 RewriteEntry &Entry = RewriteMap[Expr];
10664 // If we already have an entry and the version matches, return it.
10665 if (Entry.second && Generation == Entry.first)
10666 return Entry.second;
10668 // We found an entry but it's stale. Rewrite the stale entry
10669 // according to the current predicate.
10671 Expr = Entry.second;
10673 const SCEV *NewSCEV = SE.rewriteUsingPredicate(Expr, &L, Preds);
10674 Entry = {Generation, NewSCEV};
10679 const SCEV *PredicatedScalarEvolution::getBackedgeTakenCount() {
10680 if (!BackedgeCount) {
10681 SCEVUnionPredicate BackedgePred;
10682 BackedgeCount = SE.getPredicatedBackedgeTakenCount(&L, BackedgePred);
10683 addPredicate(BackedgePred);
10685 return BackedgeCount;
10688 void PredicatedScalarEvolution::addPredicate(const SCEVPredicate &Pred) {
10689 if (Preds.implies(&Pred))
10692 updateGeneration();
10695 const SCEVUnionPredicate &PredicatedScalarEvolution::getUnionPredicate() const {
10699 void PredicatedScalarEvolution::updateGeneration() {
10700 // If the generation number wrapped recompute everything.
10701 if (++Generation == 0) {
10702 for (auto &II : RewriteMap) {
10703 const SCEV *Rewritten = II.second.second;
10704 II.second = {Generation, SE.rewriteUsingPredicate(Rewritten, &L, Preds)};
10709 void PredicatedScalarEvolution::setNoOverflow(
10710 Value *V, SCEVWrapPredicate::IncrementWrapFlags Flags) {
10711 const SCEV *Expr = getSCEV(V);
10712 const auto *AR = cast<SCEVAddRecExpr>(Expr);
10714 auto ImpliedFlags = SCEVWrapPredicate::getImpliedFlags(AR, SE);
10716 // Clear the statically implied flags.
10717 Flags = SCEVWrapPredicate::clearFlags(Flags, ImpliedFlags);
10718 addPredicate(*SE.getWrapPredicate(AR, Flags));
10720 auto II = FlagsMap.insert({V, Flags});
10722 II.first->second = SCEVWrapPredicate::setFlags(Flags, II.first->second);
10725 bool PredicatedScalarEvolution::hasNoOverflow(
10726 Value *V, SCEVWrapPredicate::IncrementWrapFlags Flags) {
10727 const SCEV *Expr = getSCEV(V);
10728 const auto *AR = cast<SCEVAddRecExpr>(Expr);
10730 Flags = SCEVWrapPredicate::clearFlags(
10731 Flags, SCEVWrapPredicate::getImpliedFlags(AR, SE));
10733 auto II = FlagsMap.find(V);
10735 if (II != FlagsMap.end())
10736 Flags = SCEVWrapPredicate::clearFlags(Flags, II->second);
10738 return Flags == SCEVWrapPredicate::IncrementAnyWrap;
10741 const SCEVAddRecExpr *PredicatedScalarEvolution::getAsAddRec(Value *V) {
10742 const SCEV *Expr = this->getSCEV(V);
10743 SmallPtrSet<const SCEVPredicate *, 4> NewPreds;
10744 auto *New = SE.convertSCEVToAddRecWithPredicates(Expr, &L, NewPreds);
10749 for (auto *P : NewPreds)
10752 updateGeneration();
10753 RewriteMap[SE.getSCEV(V)] = {Generation, New};
10757 PredicatedScalarEvolution::PredicatedScalarEvolution(
10758 const PredicatedScalarEvolution &Init)
10759 : RewriteMap(Init.RewriteMap), SE(Init.SE), L(Init.L), Preds(Init.Preds),
10760 Generation(Init.Generation), BackedgeCount(Init.BackedgeCount) {
10761 for (const auto &I : Init.FlagsMap)
10762 FlagsMap.insert(I);
10765 void PredicatedScalarEvolution::print(raw_ostream &OS, unsigned Depth) const {
10767 for (auto *BB : L.getBlocks())
10768 for (auto &I : *BB) {
10769 if (!SE.isSCEVable(I.getType()))
10772 auto *Expr = SE.getSCEV(&I);
10773 auto II = RewriteMap.find(Expr);
10775 if (II == RewriteMap.end())
10778 // Don't print things that are not interesting.
10779 if (II->second.second == Expr)
10782 OS.indent(Depth) << "[PSE]" << I << ":\n";
10783 OS.indent(Depth + 2) << *Expr << "\n";
10784 OS.indent(Depth + 2) << "--> " << *II->second.second << "\n";