1 //===- ValueTracking.cpp - Walk computations to compute properties --------===//
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 routines that help analyze properties that chains of
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Analysis/ValueTracking.h"
16 #include "llvm/ADT/APFloat.h"
17 #include "llvm/ADT/APInt.h"
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/ADT/None.h"
20 #include "llvm/ADT/Optional.h"
21 #include "llvm/ADT/STLExtras.h"
22 #include "llvm/ADT/SmallPtrSet.h"
23 #include "llvm/ADT/SmallSet.h"
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/ADT/StringRef.h"
26 #include "llvm/ADT/iterator_range.h"
27 #include "llvm/Analysis/AliasAnalysis.h"
28 #include "llvm/Analysis/AssumptionCache.h"
29 #include "llvm/Analysis/GuardUtils.h"
30 #include "llvm/Analysis/InstructionSimplify.h"
31 #include "llvm/Analysis/Loads.h"
32 #include "llvm/Analysis/LoopInfo.h"
33 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
34 #include "llvm/Analysis/TargetLibraryInfo.h"
35 #include "llvm/IR/Argument.h"
36 #include "llvm/IR/Attributes.h"
37 #include "llvm/IR/BasicBlock.h"
38 #include "llvm/IR/CallSite.h"
39 #include "llvm/IR/Constant.h"
40 #include "llvm/IR/ConstantRange.h"
41 #include "llvm/IR/Constants.h"
42 #include "llvm/IR/DataLayout.h"
43 #include "llvm/IR/DerivedTypes.h"
44 #include "llvm/IR/DiagnosticInfo.h"
45 #include "llvm/IR/Dominators.h"
46 #include "llvm/IR/Function.h"
47 #include "llvm/IR/GetElementPtrTypeIterator.h"
48 #include "llvm/IR/GlobalAlias.h"
49 #include "llvm/IR/GlobalValue.h"
50 #include "llvm/IR/GlobalVariable.h"
51 #include "llvm/IR/InstrTypes.h"
52 #include "llvm/IR/Instruction.h"
53 #include "llvm/IR/Instructions.h"
54 #include "llvm/IR/IntrinsicInst.h"
55 #include "llvm/IR/Intrinsics.h"
56 #include "llvm/IR/LLVMContext.h"
57 #include "llvm/IR/Metadata.h"
58 #include "llvm/IR/Module.h"
59 #include "llvm/IR/Operator.h"
60 #include "llvm/IR/PatternMatch.h"
61 #include "llvm/IR/Type.h"
62 #include "llvm/IR/User.h"
63 #include "llvm/IR/Value.h"
64 #include "llvm/Support/Casting.h"
65 #include "llvm/Support/CommandLine.h"
66 #include "llvm/Support/Compiler.h"
67 #include "llvm/Support/ErrorHandling.h"
68 #include "llvm/Support/KnownBits.h"
69 #include "llvm/Support/MathExtras.h"
78 using namespace llvm::PatternMatch;
80 const unsigned MaxDepth = 6;
82 // Controls the number of uses of the value searched for possible
83 // dominating comparisons.
84 static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses",
85 cl::Hidden, cl::init(20));
87 /// Returns the bitwidth of the given scalar or pointer type. For vector types,
88 /// returns the element type's bitwidth.
89 static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
90 if (unsigned BitWidth = Ty->getScalarSizeInBits())
93 return DL.getIndexTypeSizeInBits(Ty);
98 // Simplifying using an assume can only be done in a particular control-flow
99 // context (the context instruction provides that context). If an assume and
100 // the context instruction are not in the same block then the DT helps in
101 // figuring out if we can use it.
103 const DataLayout &DL;
105 const Instruction *CxtI;
106 const DominatorTree *DT;
108 // Unlike the other analyses, this may be a nullptr because not all clients
109 // provide it currently.
110 OptimizationRemarkEmitter *ORE;
112 /// Set of assumptions that should be excluded from further queries.
113 /// This is because of the potential for mutual recursion to cause
114 /// computeKnownBits to repeatedly visit the same assume intrinsic. The
115 /// classic case of this is assume(x = y), which will attempt to determine
116 /// bits in x from bits in y, which will attempt to determine bits in y from
117 /// bits in x, etc. Regarding the mutual recursion, computeKnownBits can call
118 /// isKnownNonZero, which calls computeKnownBits and isKnownToBeAPowerOfTwo
119 /// (all of which can call computeKnownBits), and so on.
120 std::array<const Value *, MaxDepth> Excluded;
122 /// If true, it is safe to use metadata during simplification.
125 unsigned NumExcluded = 0;
127 Query(const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI,
128 const DominatorTree *DT, bool UseInstrInfo,
129 OptimizationRemarkEmitter *ORE = nullptr)
130 : DL(DL), AC(AC), CxtI(CxtI), DT(DT), ORE(ORE), IIQ(UseInstrInfo) {}
132 Query(const Query &Q, const Value *NewExcl)
133 : DL(Q.DL), AC(Q.AC), CxtI(Q.CxtI), DT(Q.DT), ORE(Q.ORE), IIQ(Q.IIQ),
134 NumExcluded(Q.NumExcluded) {
135 Excluded = Q.Excluded;
136 Excluded[NumExcluded++] = NewExcl;
137 assert(NumExcluded <= Excluded.size());
140 bool isExcluded(const Value *Value) const {
141 if (NumExcluded == 0)
143 auto End = Excluded.begin() + NumExcluded;
144 return std::find(Excluded.begin(), End, Value) != End;
148 } // end anonymous namespace
150 // Given the provided Value and, potentially, a context instruction, return
151 // the preferred context instruction (if any).
152 static const Instruction *safeCxtI(const Value *V, const Instruction *CxtI) {
153 // If we've been provided with a context instruction, then use that (provided
154 // it has been inserted).
155 if (CxtI && CxtI->getParent())
158 // If the value is really an already-inserted instruction, then use that.
159 CxtI = dyn_cast<Instruction>(V);
160 if (CxtI && CxtI->getParent())
166 static void computeKnownBits(const Value *V, KnownBits &Known,
167 unsigned Depth, const Query &Q);
169 void llvm::computeKnownBits(const Value *V, KnownBits &Known,
170 const DataLayout &DL, unsigned Depth,
171 AssumptionCache *AC, const Instruction *CxtI,
172 const DominatorTree *DT,
173 OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
174 ::computeKnownBits(V, Known, Depth,
175 Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
178 static KnownBits computeKnownBits(const Value *V, unsigned Depth,
181 KnownBits llvm::computeKnownBits(const Value *V, const DataLayout &DL,
182 unsigned Depth, AssumptionCache *AC,
183 const Instruction *CxtI,
184 const DominatorTree *DT,
185 OptimizationRemarkEmitter *ORE,
187 return ::computeKnownBits(
188 V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
191 bool llvm::haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
192 const DataLayout &DL, AssumptionCache *AC,
193 const Instruction *CxtI, const DominatorTree *DT,
195 assert(LHS->getType() == RHS->getType() &&
196 "LHS and RHS should have the same type");
197 assert(LHS->getType()->isIntOrIntVectorTy() &&
198 "LHS and RHS should be integers");
199 // Look for an inverted mask: (X & ~M) op (Y & M).
201 if (match(LHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
202 match(RHS, m_c_And(m_Specific(M), m_Value())))
204 if (match(RHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
205 match(LHS, m_c_And(m_Specific(M), m_Value())))
207 IntegerType *IT = cast<IntegerType>(LHS->getType()->getScalarType());
208 KnownBits LHSKnown(IT->getBitWidth());
209 KnownBits RHSKnown(IT->getBitWidth());
210 computeKnownBits(LHS, LHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
211 computeKnownBits(RHS, RHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
212 return (LHSKnown.Zero | RHSKnown.Zero).isAllOnesValue();
215 bool llvm::isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI) {
216 for (const User *U : CxtI->users()) {
217 if (const ICmpInst *IC = dyn_cast<ICmpInst>(U))
218 if (IC->isEquality())
219 if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
220 if (C->isNullValue())
227 static bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
230 bool llvm::isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
231 bool OrZero, unsigned Depth,
232 AssumptionCache *AC, const Instruction *CxtI,
233 const DominatorTree *DT, bool UseInstrInfo) {
234 return ::isKnownToBeAPowerOfTwo(
235 V, OrZero, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
238 static bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q);
240 bool llvm::isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth,
241 AssumptionCache *AC, const Instruction *CxtI,
242 const DominatorTree *DT, bool UseInstrInfo) {
243 return ::isKnownNonZero(V, Depth,
244 Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
247 bool llvm::isKnownNonNegative(const Value *V, const DataLayout &DL,
248 unsigned Depth, AssumptionCache *AC,
249 const Instruction *CxtI, const DominatorTree *DT,
252 computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
253 return Known.isNonNegative();
256 bool llvm::isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth,
257 AssumptionCache *AC, const Instruction *CxtI,
258 const DominatorTree *DT, bool UseInstrInfo) {
259 if (auto *CI = dyn_cast<ConstantInt>(V))
260 return CI->getValue().isStrictlyPositive();
262 // TODO: We'd doing two recursive queries here. We should factor this such
263 // that only a single query is needed.
264 return isKnownNonNegative(V, DL, Depth, AC, CxtI, DT, UseInstrInfo) &&
265 isKnownNonZero(V, DL, Depth, AC, CxtI, DT, UseInstrInfo);
268 bool llvm::isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth,
269 AssumptionCache *AC, const Instruction *CxtI,
270 const DominatorTree *DT, bool UseInstrInfo) {
272 computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
273 return Known.isNegative();
276 static bool isKnownNonEqual(const Value *V1, const Value *V2, const Query &Q);
278 bool llvm::isKnownNonEqual(const Value *V1, const Value *V2,
279 const DataLayout &DL, AssumptionCache *AC,
280 const Instruction *CxtI, const DominatorTree *DT,
282 return ::isKnownNonEqual(V1, V2,
283 Query(DL, AC, safeCxtI(V1, safeCxtI(V2, CxtI)), DT,
284 UseInstrInfo, /*ORE=*/nullptr));
287 static bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
290 bool llvm::MaskedValueIsZero(const Value *V, const APInt &Mask,
291 const DataLayout &DL, unsigned Depth,
292 AssumptionCache *AC, const Instruction *CxtI,
293 const DominatorTree *DT, bool UseInstrInfo) {
294 return ::MaskedValueIsZero(
295 V, Mask, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
298 static unsigned ComputeNumSignBits(const Value *V, unsigned Depth,
301 unsigned llvm::ComputeNumSignBits(const Value *V, const DataLayout &DL,
302 unsigned Depth, AssumptionCache *AC,
303 const Instruction *CxtI,
304 const DominatorTree *DT, bool UseInstrInfo) {
305 return ::ComputeNumSignBits(
306 V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
309 static void computeKnownBitsAddSub(bool Add, const Value *Op0, const Value *Op1,
311 KnownBits &KnownOut, KnownBits &Known2,
312 unsigned Depth, const Query &Q) {
313 unsigned BitWidth = KnownOut.getBitWidth();
315 // If an initial sequence of bits in the result is not needed, the
316 // corresponding bits in the operands are not needed.
317 KnownBits LHSKnown(BitWidth);
318 computeKnownBits(Op0, LHSKnown, Depth + 1, Q);
319 computeKnownBits(Op1, Known2, Depth + 1, Q);
321 KnownOut = KnownBits::computeForAddSub(Add, NSW, LHSKnown, Known2);
324 static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
325 KnownBits &Known, KnownBits &Known2,
326 unsigned Depth, const Query &Q) {
327 unsigned BitWidth = Known.getBitWidth();
328 computeKnownBits(Op1, Known, Depth + 1, Q);
329 computeKnownBits(Op0, Known2, Depth + 1, Q);
331 bool isKnownNegative = false;
332 bool isKnownNonNegative = false;
333 // If the multiplication is known not to overflow, compute the sign bit.
336 // The product of a number with itself is non-negative.
337 isKnownNonNegative = true;
339 bool isKnownNonNegativeOp1 = Known.isNonNegative();
340 bool isKnownNonNegativeOp0 = Known2.isNonNegative();
341 bool isKnownNegativeOp1 = Known.isNegative();
342 bool isKnownNegativeOp0 = Known2.isNegative();
343 // The product of two numbers with the same sign is non-negative.
344 isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) ||
345 (isKnownNonNegativeOp1 && isKnownNonNegativeOp0);
346 // The product of a negative number and a non-negative number is either
348 if (!isKnownNonNegative)
349 isKnownNegative = (isKnownNegativeOp1 && isKnownNonNegativeOp0 &&
350 isKnownNonZero(Op0, Depth, Q)) ||
351 (isKnownNegativeOp0 && isKnownNonNegativeOp1 &&
352 isKnownNonZero(Op1, Depth, Q));
356 assert(!Known.hasConflict() && !Known2.hasConflict());
357 // Compute a conservative estimate for high known-0 bits.
358 unsigned LeadZ = std::max(Known.countMinLeadingZeros() +
359 Known2.countMinLeadingZeros(),
360 BitWidth) - BitWidth;
361 LeadZ = std::min(LeadZ, BitWidth);
363 // The result of the bottom bits of an integer multiply can be
364 // inferred by looking at the bottom bits of both operands and
365 // multiplying them together.
366 // We can infer at least the minimum number of known trailing bits
367 // of both operands. Depending on number of trailing zeros, we can
368 // infer more bits, because (a*b) <=> ((a/m) * (b/n)) * (m*n) assuming
369 // a and b are divisible by m and n respectively.
370 // We then calculate how many of those bits are inferrable and set
371 // the output. For example, the i8 mul:
374 // We know the bottom 3 bits are zero since the first can be divided by
375 // 4 and the second by 2, thus having ((12/4) * (14/2)) * (2*4).
376 // Applying the multiplication to the trimmed arguments gets:
386 // Which allows us to infer the 2 LSBs. Since we're multiplying the result
387 // by 8, the bottom 3 bits will be 0, so we can infer a total of 5 bits.
388 // The proof for this can be described as:
389 // Pre: (C1 >= 0) && (C1 < (1 << C5)) && (C2 >= 0) && (C2 < (1 << C6)) &&
390 // (C7 == (1 << (umin(countTrailingZeros(C1), C5) +
391 // umin(countTrailingZeros(C2), C6) +
392 // umin(C5 - umin(countTrailingZeros(C1), C5),
393 // C6 - umin(countTrailingZeros(C2), C6)))) - 1)
394 // %aa = shl i8 %a, C5
395 // %bb = shl i8 %b, C6
396 // %aaa = or i8 %aa, C1
397 // %bbb = or i8 %bb, C2
398 // %mul = mul i8 %aaa, %bbb
399 // %mask = and i8 %mul, C7
401 // %mask = i8 ((C1*C2)&C7)
402 // Where C5, C6 describe the known bits of %a, %b
403 // C1, C2 describe the known bottom bits of %a, %b.
404 // C7 describes the mask of the known bits of the result.
405 APInt Bottom0 = Known.One;
406 APInt Bottom1 = Known2.One;
408 // How many times we'd be able to divide each argument by 2 (shr by 1).
409 // This gives us the number of trailing zeros on the multiplication result.
410 unsigned TrailBitsKnown0 = (Known.Zero | Known.One).countTrailingOnes();
411 unsigned TrailBitsKnown1 = (Known2.Zero | Known2.One).countTrailingOnes();
412 unsigned TrailZero0 = Known.countMinTrailingZeros();
413 unsigned TrailZero1 = Known2.countMinTrailingZeros();
414 unsigned TrailZ = TrailZero0 + TrailZero1;
416 // Figure out the fewest known-bits operand.
417 unsigned SmallestOperand = std::min(TrailBitsKnown0 - TrailZero0,
418 TrailBitsKnown1 - TrailZero1);
419 unsigned ResultBitsKnown = std::min(SmallestOperand + TrailZ, BitWidth);
421 APInt BottomKnown = Bottom0.getLoBits(TrailBitsKnown0) *
422 Bottom1.getLoBits(TrailBitsKnown1);
425 Known.Zero.setHighBits(LeadZ);
426 Known.Zero |= (~BottomKnown).getLoBits(ResultBitsKnown);
427 Known.One |= BottomKnown.getLoBits(ResultBitsKnown);
429 // Only make use of no-wrap flags if we failed to compute the sign bit
430 // directly. This matters if the multiplication always overflows, in
431 // which case we prefer to follow the result of the direct computation,
432 // though as the program is invoking undefined behaviour we can choose
433 // whatever we like here.
434 if (isKnownNonNegative && !Known.isNegative())
435 Known.makeNonNegative();
436 else if (isKnownNegative && !Known.isNonNegative())
437 Known.makeNegative();
440 void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
442 unsigned BitWidth = Known.getBitWidth();
443 unsigned NumRanges = Ranges.getNumOperands() / 2;
444 assert(NumRanges >= 1);
446 Known.Zero.setAllBits();
447 Known.One.setAllBits();
449 for (unsigned i = 0; i < NumRanges; ++i) {
451 mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 0));
453 mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
454 ConstantRange Range(Lower->getValue(), Upper->getValue());
456 // The first CommonPrefixBits of all values in Range are equal.
457 unsigned CommonPrefixBits =
458 (Range.getUnsignedMax() ^ Range.getUnsignedMin()).countLeadingZeros();
460 APInt Mask = APInt::getHighBitsSet(BitWidth, CommonPrefixBits);
461 Known.One &= Range.getUnsignedMax() & Mask;
462 Known.Zero &= ~Range.getUnsignedMax() & Mask;
466 static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
467 SmallVector<const Value *, 16> WorkSet(1, I);
468 SmallPtrSet<const Value *, 32> Visited;
469 SmallPtrSet<const Value *, 16> EphValues;
471 // The instruction defining an assumption's condition itself is always
472 // considered ephemeral to that assumption (even if it has other
473 // non-ephemeral users). See r246696's test case for an example.
474 if (is_contained(I->operands(), E))
477 while (!WorkSet.empty()) {
478 const Value *V = WorkSet.pop_back_val();
479 if (!Visited.insert(V).second)
482 // If all uses of this value are ephemeral, then so is this value.
483 if (llvm::all_of(V->users(), [&](const User *U) {
484 return EphValues.count(U);
489 if (V == I || isSafeToSpeculativelyExecute(V)) {
491 if (const User *U = dyn_cast<User>(V))
492 for (User::const_op_iterator J = U->op_begin(), JE = U->op_end();
494 WorkSet.push_back(*J);
502 // Is this an intrinsic that cannot be speculated but also cannot trap?
503 bool llvm::isAssumeLikeIntrinsic(const Instruction *I) {
504 if (const CallInst *CI = dyn_cast<CallInst>(I))
505 if (Function *F = CI->getCalledFunction())
506 switch (F->getIntrinsicID()) {
508 // FIXME: This list is repeated from NoTTI::getIntrinsicCost.
509 case Intrinsic::assume:
510 case Intrinsic::sideeffect:
511 case Intrinsic::dbg_declare:
512 case Intrinsic::dbg_value:
513 case Intrinsic::dbg_label:
514 case Intrinsic::invariant_start:
515 case Intrinsic::invariant_end:
516 case Intrinsic::lifetime_start:
517 case Intrinsic::lifetime_end:
518 case Intrinsic::objectsize:
519 case Intrinsic::ptr_annotation:
520 case Intrinsic::var_annotation:
527 bool llvm::isValidAssumeForContext(const Instruction *Inv,
528 const Instruction *CxtI,
529 const DominatorTree *DT) {
530 // There are two restrictions on the use of an assume:
531 // 1. The assume must dominate the context (or the control flow must
532 // reach the assume whenever it reaches the context).
533 // 2. The context must not be in the assume's set of ephemeral values
534 // (otherwise we will use the assume to prove that the condition
535 // feeding the assume is trivially true, thus causing the removal of
539 if (DT->dominates(Inv, CxtI))
541 } else if (Inv->getParent() == CxtI->getParent()->getSinglePredecessor()) {
542 // We don't have a DT, but this trivially dominates.
546 // With or without a DT, the only remaining case we will check is if the
547 // instructions are in the same BB. Give up if that is not the case.
548 if (Inv->getParent() != CxtI->getParent())
551 // If we have a dom tree, then we now know that the assume doesn't dominate
552 // the other instruction. If we don't have a dom tree then we can check if
553 // the assume is first in the BB.
555 // Search forward from the assume until we reach the context (or the end
556 // of the block); the common case is that the assume will come first.
557 for (auto I = std::next(BasicBlock::const_iterator(Inv)),
558 IE = Inv->getParent()->end(); I != IE; ++I)
563 // The context comes first, but they're both in the same block. Make sure
564 // there is nothing in between that might interrupt the control flow.
565 for (BasicBlock::const_iterator I =
566 std::next(BasicBlock::const_iterator(CxtI)), IE(Inv);
568 if (!isSafeToSpeculativelyExecute(&*I) && !isAssumeLikeIntrinsic(&*I))
571 return !isEphemeralValueOf(Inv, CxtI);
574 static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
575 unsigned Depth, const Query &Q) {
576 // Use of assumptions is context-sensitive. If we don't have a context, we
578 if (!Q.AC || !Q.CxtI)
581 unsigned BitWidth = Known.getBitWidth();
583 // Note that the patterns below need to be kept in sync with the code
584 // in AssumptionCache::updateAffectedValues.
586 for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
589 CallInst *I = cast<CallInst>(AssumeVH);
590 assert(I->getParent()->getParent() == Q.CxtI->getParent()->getParent() &&
591 "Got assumption for the wrong function!");
595 // Warning: This loop can end up being somewhat performance sensitive.
596 // We're running this loop for once for each value queried resulting in a
597 // runtime of ~O(#assumes * #values).
599 assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
600 "must be an assume intrinsic");
602 Value *Arg = I->getArgOperand(0);
604 if (Arg == V && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
605 assert(BitWidth == 1 && "assume operand is not i1?");
609 if (match(Arg, m_Not(m_Specific(V))) &&
610 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
611 assert(BitWidth == 1 && "assume operand is not i1?");
616 // The remaining tests are all recursive, so bail out if we hit the limit.
617 if (Depth == MaxDepth)
621 auto m_V = m_CombineOr(m_Specific(V),
622 m_CombineOr(m_PtrToInt(m_Specific(V)),
623 m_BitCast(m_Specific(V))));
625 CmpInst::Predicate Pred;
628 if (match(Arg, m_c_ICmp(Pred, m_V, m_Value(A))) &&
629 Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
630 KnownBits RHSKnown(BitWidth);
631 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
632 Known.Zero |= RHSKnown.Zero;
633 Known.One |= RHSKnown.One;
635 } else if (match(Arg,
636 m_c_ICmp(Pred, m_c_And(m_V, m_Value(B)), m_Value(A))) &&
637 Pred == ICmpInst::ICMP_EQ &&
638 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
639 KnownBits RHSKnown(BitWidth);
640 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
641 KnownBits MaskKnown(BitWidth);
642 computeKnownBits(B, MaskKnown, Depth+1, Query(Q, I));
644 // For those bits in the mask that are known to be one, we can propagate
645 // known bits from the RHS to V.
646 Known.Zero |= RHSKnown.Zero & MaskKnown.One;
647 Known.One |= RHSKnown.One & MaskKnown.One;
648 // assume(~(v & b) = a)
649 } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_c_And(m_V, m_Value(B))),
651 Pred == ICmpInst::ICMP_EQ &&
652 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
653 KnownBits RHSKnown(BitWidth);
654 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
655 KnownBits MaskKnown(BitWidth);
656 computeKnownBits(B, MaskKnown, Depth+1, Query(Q, I));
658 // For those bits in the mask that are known to be one, we can propagate
659 // inverted known bits from the RHS to V.
660 Known.Zero |= RHSKnown.One & MaskKnown.One;
661 Known.One |= RHSKnown.Zero & MaskKnown.One;
663 } else if (match(Arg,
664 m_c_ICmp(Pred, m_c_Or(m_V, m_Value(B)), m_Value(A))) &&
665 Pred == ICmpInst::ICMP_EQ &&
666 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
667 KnownBits RHSKnown(BitWidth);
668 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
669 KnownBits BKnown(BitWidth);
670 computeKnownBits(B, BKnown, Depth+1, Query(Q, I));
672 // For those bits in B that are known to be zero, we can propagate known
673 // bits from the RHS to V.
674 Known.Zero |= RHSKnown.Zero & BKnown.Zero;
675 Known.One |= RHSKnown.One & BKnown.Zero;
676 // assume(~(v | b) = a)
677 } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_c_Or(m_V, m_Value(B))),
679 Pred == ICmpInst::ICMP_EQ &&
680 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
681 KnownBits RHSKnown(BitWidth);
682 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
683 KnownBits BKnown(BitWidth);
684 computeKnownBits(B, BKnown, Depth+1, Query(Q, I));
686 // For those bits in B that are known to be zero, we can propagate
687 // inverted known bits from the RHS to V.
688 Known.Zero |= RHSKnown.One & BKnown.Zero;
689 Known.One |= RHSKnown.Zero & BKnown.Zero;
691 } else if (match(Arg,
692 m_c_ICmp(Pred, m_c_Xor(m_V, m_Value(B)), m_Value(A))) &&
693 Pred == ICmpInst::ICMP_EQ &&
694 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
695 KnownBits RHSKnown(BitWidth);
696 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
697 KnownBits BKnown(BitWidth);
698 computeKnownBits(B, BKnown, Depth+1, Query(Q, I));
700 // For those bits in B that are known to be zero, we can propagate known
701 // bits from the RHS to V. For those bits in B that are known to be one,
702 // we can propagate inverted known bits from the RHS to V.
703 Known.Zero |= RHSKnown.Zero & BKnown.Zero;
704 Known.One |= RHSKnown.One & BKnown.Zero;
705 Known.Zero |= RHSKnown.One & BKnown.One;
706 Known.One |= RHSKnown.Zero & BKnown.One;
707 // assume(~(v ^ b) = a)
708 } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_c_Xor(m_V, m_Value(B))),
710 Pred == ICmpInst::ICMP_EQ &&
711 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
712 KnownBits RHSKnown(BitWidth);
713 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
714 KnownBits BKnown(BitWidth);
715 computeKnownBits(B, BKnown, Depth+1, Query(Q, I));
717 // For those bits in B that are known to be zero, we can propagate
718 // inverted known bits from the RHS to V. For those bits in B that are
719 // known to be one, we can propagate known bits from the RHS to V.
720 Known.Zero |= RHSKnown.One & BKnown.Zero;
721 Known.One |= RHSKnown.Zero & BKnown.Zero;
722 Known.Zero |= RHSKnown.Zero & BKnown.One;
723 Known.One |= RHSKnown.One & BKnown.One;
724 // assume(v << c = a)
725 } else if (match(Arg, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
727 Pred == ICmpInst::ICMP_EQ &&
728 isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
730 KnownBits RHSKnown(BitWidth);
731 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
732 // For those bits in RHS that are known, we can propagate them to known
733 // bits in V shifted to the right by C.
734 RHSKnown.Zero.lshrInPlace(C);
735 Known.Zero |= RHSKnown.Zero;
736 RHSKnown.One.lshrInPlace(C);
737 Known.One |= RHSKnown.One;
738 // assume(~(v << c) = a)
739 } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
741 Pred == ICmpInst::ICMP_EQ &&
742 isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
744 KnownBits RHSKnown(BitWidth);
745 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
746 // For those bits in RHS that are known, we can propagate them inverted
747 // to known bits in V shifted to the right by C.
748 RHSKnown.One.lshrInPlace(C);
749 Known.Zero |= RHSKnown.One;
750 RHSKnown.Zero.lshrInPlace(C);
751 Known.One |= RHSKnown.Zero;
752 // assume(v >> c = a)
753 } else if (match(Arg,
754 m_c_ICmp(Pred, m_Shr(m_V, m_ConstantInt(C)),
756 Pred == ICmpInst::ICMP_EQ &&
757 isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
759 KnownBits RHSKnown(BitWidth);
760 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
761 // For those bits in RHS that are known, we can propagate them to known
762 // bits in V shifted to the right by C.
763 Known.Zero |= RHSKnown.Zero << C;
764 Known.One |= RHSKnown.One << C;
765 // assume(~(v >> c) = a)
766 } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shr(m_V, m_ConstantInt(C))),
768 Pred == ICmpInst::ICMP_EQ &&
769 isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
771 KnownBits RHSKnown(BitWidth);
772 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
773 // For those bits in RHS that are known, we can propagate them inverted
774 // to known bits in V shifted to the right by C.
775 Known.Zero |= RHSKnown.One << C;
776 Known.One |= RHSKnown.Zero << C;
777 // assume(v >=_s c) where c is non-negative
778 } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
779 Pred == ICmpInst::ICMP_SGE &&
780 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
781 KnownBits RHSKnown(BitWidth);
782 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
784 if (RHSKnown.isNonNegative()) {
785 // We know that the sign bit is zero.
786 Known.makeNonNegative();
788 // assume(v >_s c) where c is at least -1.
789 } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
790 Pred == ICmpInst::ICMP_SGT &&
791 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
792 KnownBits RHSKnown(BitWidth);
793 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
795 if (RHSKnown.isAllOnes() || RHSKnown.isNonNegative()) {
796 // We know that the sign bit is zero.
797 Known.makeNonNegative();
799 // assume(v <=_s c) where c is negative
800 } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
801 Pred == ICmpInst::ICMP_SLE &&
802 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
803 KnownBits RHSKnown(BitWidth);
804 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
806 if (RHSKnown.isNegative()) {
807 // We know that the sign bit is one.
808 Known.makeNegative();
810 // assume(v <_s c) where c is non-positive
811 } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
812 Pred == ICmpInst::ICMP_SLT &&
813 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
814 KnownBits RHSKnown(BitWidth);
815 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
817 if (RHSKnown.isZero() || RHSKnown.isNegative()) {
818 // We know that the sign bit is one.
819 Known.makeNegative();
822 } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
823 Pred == ICmpInst::ICMP_ULE &&
824 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
825 KnownBits RHSKnown(BitWidth);
826 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
828 // Whatever high bits in c are zero are known to be zero.
829 Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
831 } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
832 Pred == ICmpInst::ICMP_ULT &&
833 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
834 KnownBits RHSKnown(BitWidth);
835 computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
837 // If the RHS is known zero, then this assumption must be wrong (nothing
838 // is unsigned less than zero). Signal a conflict and get out of here.
839 if (RHSKnown.isZero()) {
840 Known.Zero.setAllBits();
841 Known.One.setAllBits();
845 // Whatever high bits in c are zero are known to be zero (if c is a power
846 // of 2, then one more).
847 if (isKnownToBeAPowerOfTwo(A, false, Depth + 1, Query(Q, I)))
848 Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros() + 1);
850 Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
854 // If assumptions conflict with each other or previous known bits, then we
855 // have a logical fallacy. It's possible that the assumption is not reachable,
856 // so this isn't a real bug. On the other hand, the program may have undefined
857 // behavior, or we might have a bug in the compiler. We can't assert/crash, so
858 // clear out the known bits, try to warn the user, and hope for the best.
859 if (Known.Zero.intersects(Known.One)) {
864 auto *CxtI = const_cast<Instruction *>(Q.CxtI);
865 return OptimizationRemarkAnalysis("value-tracking", "BadAssumption",
867 << "Detected conflicting code assumptions. Program may "
868 "have undefined behavior, or compiler may have "
874 /// Compute known bits from a shift operator, including those with a
875 /// non-constant shift amount. Known is the output of this function. Known2 is a
876 /// pre-allocated temporary with the same bit width as Known. KZF and KOF are
877 /// operator-specific functions that, given the known-zero or known-one bits
878 /// respectively, and a shift amount, compute the implied known-zero or
879 /// known-one bits of the shift operator's result respectively for that shift
880 /// amount. The results from calling KZF and KOF are conservatively combined for
881 /// all permitted shift amounts.
882 static void computeKnownBitsFromShiftOperator(
883 const Operator *I, KnownBits &Known, KnownBits &Known2,
884 unsigned Depth, const Query &Q,
885 function_ref<APInt(const APInt &, unsigned)> KZF,
886 function_ref<APInt(const APInt &, unsigned)> KOF) {
887 unsigned BitWidth = Known.getBitWidth();
889 if (auto *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
890 unsigned ShiftAmt = SA->getLimitedValue(BitWidth-1);
892 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
893 Known.Zero = KZF(Known.Zero, ShiftAmt);
894 Known.One = KOF(Known.One, ShiftAmt);
895 // If the known bits conflict, this must be an overflowing left shift, so
896 // the shift result is poison. We can return anything we want. Choose 0 for
897 // the best folding opportunity.
898 if (Known.hasConflict())
904 computeKnownBits(I->getOperand(1), Known, Depth + 1, Q);
906 // If the shift amount could be greater than or equal to the bit-width of the
907 // LHS, the value could be poison, but bail out because the check below is
908 // expensive. TODO: Should we just carry on?
909 if ((~Known.Zero).uge(BitWidth)) {
914 // Note: We cannot use Known.Zero.getLimitedValue() here, because if
915 // BitWidth > 64 and any upper bits are known, we'll end up returning the
916 // limit value (which implies all bits are known).
917 uint64_t ShiftAmtKZ = Known.Zero.zextOrTrunc(64).getZExtValue();
918 uint64_t ShiftAmtKO = Known.One.zextOrTrunc(64).getZExtValue();
920 // It would be more-clearly correct to use the two temporaries for this
921 // calculation. Reusing the APInts here to prevent unnecessary allocations.
924 // If we know the shifter operand is nonzero, we can sometimes infer more
925 // known bits. However this is expensive to compute, so be lazy about it and
926 // only compute it when absolutely necessary.
927 Optional<bool> ShifterOperandIsNonZero;
929 // Early exit if we can't constrain any well-defined shift amount.
930 if (!(ShiftAmtKZ & (PowerOf2Ceil(BitWidth) - 1)) &&
931 !(ShiftAmtKO & (PowerOf2Ceil(BitWidth) - 1))) {
932 ShifterOperandIsNonZero = isKnownNonZero(I->getOperand(1), Depth + 1, Q);
933 if (!*ShifterOperandIsNonZero)
937 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
939 Known.Zero.setAllBits();
940 Known.One.setAllBits();
941 for (unsigned ShiftAmt = 0; ShiftAmt < BitWidth; ++ShiftAmt) {
942 // Combine the shifted known input bits only for those shift amounts
943 // compatible with its known constraints.
944 if ((ShiftAmt & ~ShiftAmtKZ) != ShiftAmt)
946 if ((ShiftAmt | ShiftAmtKO) != ShiftAmt)
948 // If we know the shifter is nonzero, we may be able to infer more known
949 // bits. This check is sunk down as far as possible to avoid the expensive
950 // call to isKnownNonZero if the cheaper checks above fail.
952 if (!ShifterOperandIsNonZero.hasValue())
953 ShifterOperandIsNonZero =
954 isKnownNonZero(I->getOperand(1), Depth + 1, Q);
955 if (*ShifterOperandIsNonZero)
959 Known.Zero &= KZF(Known2.Zero, ShiftAmt);
960 Known.One &= KOF(Known2.One, ShiftAmt);
963 // If the known bits conflict, the result is poison. Return a 0 and hope the
964 // caller can further optimize that.
965 if (Known.hasConflict())
969 static void computeKnownBitsFromOperator(const Operator *I, KnownBits &Known,
970 unsigned Depth, const Query &Q) {
971 unsigned BitWidth = Known.getBitWidth();
973 KnownBits Known2(Known);
974 switch (I->getOpcode()) {
976 case Instruction::Load:
978 Q.IIQ.getMetadata(cast<LoadInst>(I), LLVMContext::MD_range))
979 computeKnownBitsFromRangeMetadata(*MD, Known);
981 case Instruction::And: {
982 // If either the LHS or the RHS are Zero, the result is zero.
983 computeKnownBits(I->getOperand(1), Known, Depth + 1, Q);
984 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
986 // Output known-1 bits are only known if set in both the LHS & RHS.
987 Known.One &= Known2.One;
988 // Output known-0 are known to be clear if zero in either the LHS | RHS.
989 Known.Zero |= Known2.Zero;
991 // and(x, add (x, -1)) is a common idiom that always clears the low bit;
992 // here we handle the more general case of adding any odd number by
993 // matching the form add(x, add(x, y)) where y is odd.
994 // TODO: This could be generalized to clearing any bit set in y where the
995 // following bit is known to be unset in y.
996 Value *X = nullptr, *Y = nullptr;
997 if (!Known.Zero[0] && !Known.One[0] &&
998 match(I, m_c_BinOp(m_Value(X), m_Add(m_Deferred(X), m_Value(Y))))) {
1000 computeKnownBits(Y, Known2, Depth + 1, Q);
1001 if (Known2.countMinTrailingOnes() > 0)
1002 Known.Zero.setBit(0);
1006 case Instruction::Or:
1007 computeKnownBits(I->getOperand(1), Known, Depth + 1, Q);
1008 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1010 // Output known-0 bits are only known if clear in both the LHS & RHS.
1011 Known.Zero &= Known2.Zero;
1012 // Output known-1 are known to be set if set in either the LHS | RHS.
1013 Known.One |= Known2.One;
1015 case Instruction::Xor: {
1016 computeKnownBits(I->getOperand(1), Known, Depth + 1, Q);
1017 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1019 // Output known-0 bits are known if clear or set in both the LHS & RHS.
1020 APInt KnownZeroOut = (Known.Zero & Known2.Zero) | (Known.One & Known2.One);
1021 // Output known-1 are known to be set if set in only one of the LHS, RHS.
1022 Known.One = (Known.Zero & Known2.One) | (Known.One & Known2.Zero);
1023 Known.Zero = std::move(KnownZeroOut);
1026 case Instruction::Mul: {
1027 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1028 computeKnownBitsMul(I->getOperand(0), I->getOperand(1), NSW, Known,
1032 case Instruction::UDiv: {
1033 // For the purposes of computing leading zeros we can conservatively
1034 // treat a udiv as a logical right shift by the power of 2 known to
1035 // be less than the denominator.
1036 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1037 unsigned LeadZ = Known2.countMinLeadingZeros();
1040 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1041 unsigned RHSMaxLeadingZeros = Known2.countMaxLeadingZeros();
1042 if (RHSMaxLeadingZeros != BitWidth)
1043 LeadZ = std::min(BitWidth, LeadZ + BitWidth - RHSMaxLeadingZeros - 1);
1045 Known.Zero.setHighBits(LeadZ);
1048 case Instruction::Select: {
1049 const Value *LHS, *RHS;
1050 SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor;
1051 if (SelectPatternResult::isMinOrMax(SPF)) {
1052 computeKnownBits(RHS, Known, Depth + 1, Q);
1053 computeKnownBits(LHS, Known2, Depth + 1, Q);
1055 computeKnownBits(I->getOperand(2), Known, Depth + 1, Q);
1056 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1059 unsigned MaxHighOnes = 0;
1060 unsigned MaxHighZeros = 0;
1061 if (SPF == SPF_SMAX) {
1062 // If both sides are negative, the result is negative.
1063 if (Known.isNegative() && Known2.isNegative())
1064 // We can derive a lower bound on the result by taking the max of the
1065 // leading one bits.
1067 std::max(Known.countMinLeadingOnes(), Known2.countMinLeadingOnes());
1068 // If either side is non-negative, the result is non-negative.
1069 else if (Known.isNonNegative() || Known2.isNonNegative())
1071 } else if (SPF == SPF_SMIN) {
1072 // If both sides are non-negative, the result is non-negative.
1073 if (Known.isNonNegative() && Known2.isNonNegative())
1074 // We can derive an upper bound on the result by taking the max of the
1075 // leading zero bits.
1076 MaxHighZeros = std::max(Known.countMinLeadingZeros(),
1077 Known2.countMinLeadingZeros());
1078 // If either side is negative, the result is negative.
1079 else if (Known.isNegative() || Known2.isNegative())
1081 } else if (SPF == SPF_UMAX) {
1082 // We can derive a lower bound on the result by taking the max of the
1083 // leading one bits.
1085 std::max(Known.countMinLeadingOnes(), Known2.countMinLeadingOnes());
1086 } else if (SPF == SPF_UMIN) {
1087 // We can derive an upper bound on the result by taking the max of the
1088 // leading zero bits.
1090 std::max(Known.countMinLeadingZeros(), Known2.countMinLeadingZeros());
1091 } else if (SPF == SPF_ABS) {
1092 // RHS from matchSelectPattern returns the negation part of abs pattern.
1093 // If the negate has an NSW flag we can assume the sign bit of the result
1094 // will be 0 because that makes abs(INT_MIN) undefined.
1095 if (Q.IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
1099 // Only known if known in both the LHS and RHS.
1100 Known.One &= Known2.One;
1101 Known.Zero &= Known2.Zero;
1102 if (MaxHighOnes > 0)
1103 Known.One.setHighBits(MaxHighOnes);
1104 if (MaxHighZeros > 0)
1105 Known.Zero.setHighBits(MaxHighZeros);
1108 case Instruction::FPTrunc:
1109 case Instruction::FPExt:
1110 case Instruction::FPToUI:
1111 case Instruction::FPToSI:
1112 case Instruction::SIToFP:
1113 case Instruction::UIToFP:
1114 break; // Can't work with floating point.
1115 case Instruction::PtrToInt:
1116 case Instruction::IntToPtr:
1117 // Fall through and handle them the same as zext/trunc.
1119 case Instruction::ZExt:
1120 case Instruction::Trunc: {
1121 Type *SrcTy = I->getOperand(0)->getType();
1123 unsigned SrcBitWidth;
1124 // Note that we handle pointer operands here because of inttoptr/ptrtoint
1125 // which fall through here.
1126 Type *ScalarTy = SrcTy->getScalarType();
1127 SrcBitWidth = ScalarTy->isPointerTy() ?
1128 Q.DL.getIndexTypeSizeInBits(ScalarTy) :
1129 Q.DL.getTypeSizeInBits(ScalarTy);
1131 assert(SrcBitWidth && "SrcBitWidth can't be zero");
1132 Known = Known.zextOrTrunc(SrcBitWidth);
1133 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1134 Known = Known.zextOrTrunc(BitWidth);
1135 // Any top bits are known to be zero.
1136 if (BitWidth > SrcBitWidth)
1137 Known.Zero.setBitsFrom(SrcBitWidth);
1140 case Instruction::BitCast: {
1141 Type *SrcTy = I->getOperand(0)->getType();
1142 if (SrcTy->isIntOrPtrTy() &&
1143 // TODO: For now, not handling conversions like:
1144 // (bitcast i64 %x to <2 x i32>)
1145 !I->getType()->isVectorTy()) {
1146 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1151 case Instruction::SExt: {
1152 // Compute the bits in the result that are not present in the input.
1153 unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
1155 Known = Known.trunc(SrcBitWidth);
1156 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1157 // If the sign bit of the input is known set or clear, then we know the
1158 // top bits of the result.
1159 Known = Known.sext(BitWidth);
1162 case Instruction::Shl: {
1163 // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
1164 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1165 auto KZF = [NSW](const APInt &KnownZero, unsigned ShiftAmt) {
1166 APInt KZResult = KnownZero << ShiftAmt;
1167 KZResult.setLowBits(ShiftAmt); // Low bits known 0.
1168 // If this shift has "nsw" keyword, then the result is either a poison
1169 // value or has the same sign bit as the first operand.
1170 if (NSW && KnownZero.isSignBitSet())
1171 KZResult.setSignBit();
1175 auto KOF = [NSW](const APInt &KnownOne, unsigned ShiftAmt) {
1176 APInt KOResult = KnownOne << ShiftAmt;
1177 if (NSW && KnownOne.isSignBitSet())
1178 KOResult.setSignBit();
1182 computeKnownBitsFromShiftOperator(I, Known, Known2, Depth, Q, KZF, KOF);
1185 case Instruction::LShr: {
1186 // (lshr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
1187 auto KZF = [](const APInt &KnownZero, unsigned ShiftAmt) {
1188 APInt KZResult = KnownZero.lshr(ShiftAmt);
1189 // High bits known zero.
1190 KZResult.setHighBits(ShiftAmt);
1194 auto KOF = [](const APInt &KnownOne, unsigned ShiftAmt) {
1195 return KnownOne.lshr(ShiftAmt);
1198 computeKnownBitsFromShiftOperator(I, Known, Known2, Depth, Q, KZF, KOF);
1201 case Instruction::AShr: {
1202 // (ashr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
1203 auto KZF = [](const APInt &KnownZero, unsigned ShiftAmt) {
1204 return KnownZero.ashr(ShiftAmt);
1207 auto KOF = [](const APInt &KnownOne, unsigned ShiftAmt) {
1208 return KnownOne.ashr(ShiftAmt);
1211 computeKnownBitsFromShiftOperator(I, Known, Known2, Depth, Q, KZF, KOF);
1214 case Instruction::Sub: {
1215 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1216 computeKnownBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW,
1217 Known, Known2, Depth, Q);
1220 case Instruction::Add: {
1221 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1222 computeKnownBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW,
1223 Known, Known2, Depth, Q);
1226 case Instruction::SRem:
1227 if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
1228 APInt RA = Rem->getValue().abs();
1229 if (RA.isPowerOf2()) {
1230 APInt LowBits = RA - 1;
1231 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1233 // The low bits of the first operand are unchanged by the srem.
1234 Known.Zero = Known2.Zero & LowBits;
1235 Known.One = Known2.One & LowBits;
1237 // If the first operand is non-negative or has all low bits zero, then
1238 // the upper bits are all zero.
1239 if (Known2.isNonNegative() || LowBits.isSubsetOf(Known2.Zero))
1240 Known.Zero |= ~LowBits;
1242 // If the first operand is negative and not all low bits are zero, then
1243 // the upper bits are all one.
1244 if (Known2.isNegative() && LowBits.intersects(Known2.One))
1245 Known.One |= ~LowBits;
1247 assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?");
1252 // The sign bit is the LHS's sign bit, except when the result of the
1253 // remainder is zero.
1254 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1255 // If it's known zero, our sign bit is also zero.
1256 if (Known2.isNonNegative())
1257 Known.makeNonNegative();
1260 case Instruction::URem: {
1261 if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
1262 const APInt &RA = Rem->getValue();
1263 if (RA.isPowerOf2()) {
1264 APInt LowBits = (RA - 1);
1265 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1266 Known.Zero |= ~LowBits;
1267 Known.One &= LowBits;
1272 // Since the result is less than or equal to either operand, any leading
1273 // zero bits in either operand must also exist in the result.
1274 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1275 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1278 std::max(Known.countMinLeadingZeros(), Known2.countMinLeadingZeros());
1280 Known.Zero.setHighBits(Leaders);
1284 case Instruction::Alloca: {
1285 const AllocaInst *AI = cast<AllocaInst>(I);
1286 unsigned Align = AI->getAlignment();
1288 Align = Q.DL.getABITypeAlignment(AI->getAllocatedType());
1291 Known.Zero.setLowBits(countTrailingZeros(Align));
1294 case Instruction::GetElementPtr: {
1295 // Analyze all of the subscripts of this getelementptr instruction
1296 // to determine if we can prove known low zero bits.
1297 KnownBits LocalKnown(BitWidth);
1298 computeKnownBits(I->getOperand(0), LocalKnown, Depth + 1, Q);
1299 unsigned TrailZ = LocalKnown.countMinTrailingZeros();
1301 gep_type_iterator GTI = gep_type_begin(I);
1302 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
1303 Value *Index = I->getOperand(i);
1304 if (StructType *STy = GTI.getStructTypeOrNull()) {
1305 // Handle struct member offset arithmetic.
1307 // Handle case when index is vector zeroinitializer
1308 Constant *CIndex = cast<Constant>(Index);
1309 if (CIndex->isZeroValue())
1312 if (CIndex->getType()->isVectorTy())
1313 Index = CIndex->getSplatValue();
1315 unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
1316 const StructLayout *SL = Q.DL.getStructLayout(STy);
1317 uint64_t Offset = SL->getElementOffset(Idx);
1318 TrailZ = std::min<unsigned>(TrailZ,
1319 countTrailingZeros(Offset));
1321 // Handle array index arithmetic.
1322 Type *IndexedTy = GTI.getIndexedType();
1323 if (!IndexedTy->isSized()) {
1327 unsigned GEPOpiBits = Index->getType()->getScalarSizeInBits();
1328 uint64_t TypeSize = Q.DL.getTypeAllocSize(IndexedTy);
1329 LocalKnown.Zero = LocalKnown.One = APInt(GEPOpiBits, 0);
1330 computeKnownBits(Index, LocalKnown, Depth + 1, Q);
1331 TrailZ = std::min(TrailZ,
1332 unsigned(countTrailingZeros(TypeSize) +
1333 LocalKnown.countMinTrailingZeros()));
1337 Known.Zero.setLowBits(TrailZ);
1340 case Instruction::PHI: {
1341 const PHINode *P = cast<PHINode>(I);
1342 // Handle the case of a simple two-predecessor recurrence PHI.
1343 // There's a lot more that could theoretically be done here, but
1344 // this is sufficient to catch some interesting cases.
1345 if (P->getNumIncomingValues() == 2) {
1346 for (unsigned i = 0; i != 2; ++i) {
1347 Value *L = P->getIncomingValue(i);
1348 Value *R = P->getIncomingValue(!i);
1349 Operator *LU = dyn_cast<Operator>(L);
1352 unsigned Opcode = LU->getOpcode();
1353 // Check for operations that have the property that if
1354 // both their operands have low zero bits, the result
1355 // will have low zero bits.
1356 if (Opcode == Instruction::Add ||
1357 Opcode == Instruction::Sub ||
1358 Opcode == Instruction::And ||
1359 Opcode == Instruction::Or ||
1360 Opcode == Instruction::Mul) {
1361 Value *LL = LU->getOperand(0);
1362 Value *LR = LU->getOperand(1);
1363 // Find a recurrence.
1370 // Ok, we have a PHI of the form L op= R. Check for low
1372 computeKnownBits(R, Known2, Depth + 1, Q);
1374 // We need to take the minimum number of known bits
1375 KnownBits Known3(Known);
1376 computeKnownBits(L, Known3, Depth + 1, Q);
1378 Known.Zero.setLowBits(std::min(Known2.countMinTrailingZeros(),
1379 Known3.countMinTrailingZeros()));
1381 auto *OverflowOp = dyn_cast<OverflowingBinaryOperator>(LU);
1382 if (OverflowOp && Q.IIQ.hasNoSignedWrap(OverflowOp)) {
1383 // If initial value of recurrence is nonnegative, and we are adding
1384 // a nonnegative number with nsw, the result can only be nonnegative
1385 // or poison value regardless of the number of times we execute the
1386 // add in phi recurrence. If initial value is negative and we are
1387 // adding a negative number with nsw, the result can only be
1388 // negative or poison value. Similar arguments apply to sub and mul.
1390 // (add non-negative, non-negative) --> non-negative
1391 // (add negative, negative) --> negative
1392 if (Opcode == Instruction::Add) {
1393 if (Known2.isNonNegative() && Known3.isNonNegative())
1394 Known.makeNonNegative();
1395 else if (Known2.isNegative() && Known3.isNegative())
1396 Known.makeNegative();
1399 // (sub nsw non-negative, negative) --> non-negative
1400 // (sub nsw negative, non-negative) --> negative
1401 else if (Opcode == Instruction::Sub && LL == I) {
1402 if (Known2.isNonNegative() && Known3.isNegative())
1403 Known.makeNonNegative();
1404 else if (Known2.isNegative() && Known3.isNonNegative())
1405 Known.makeNegative();
1408 // (mul nsw non-negative, non-negative) --> non-negative
1409 else if (Opcode == Instruction::Mul && Known2.isNonNegative() &&
1410 Known3.isNonNegative())
1411 Known.makeNonNegative();
1419 // Unreachable blocks may have zero-operand PHI nodes.
1420 if (P->getNumIncomingValues() == 0)
1423 // Otherwise take the unions of the known bit sets of the operands,
1424 // taking conservative care to avoid excessive recursion.
1425 if (Depth < MaxDepth - 1 && !Known.Zero && !Known.One) {
1426 // Skip if every incoming value references to ourself.
1427 if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
1430 Known.Zero.setAllBits();
1431 Known.One.setAllBits();
1432 for (Value *IncValue : P->incoming_values()) {
1433 // Skip direct self references.
1434 if (IncValue == P) continue;
1436 Known2 = KnownBits(BitWidth);
1437 // Recurse, but cap the recursion to one level, because we don't
1438 // want to waste time spinning around in loops.
1439 computeKnownBits(IncValue, Known2, MaxDepth - 1, Q);
1440 Known.Zero &= Known2.Zero;
1441 Known.One &= Known2.One;
1442 // If all bits have been ruled out, there's no need to check
1444 if (!Known.Zero && !Known.One)
1450 case Instruction::Call:
1451 case Instruction::Invoke:
1452 // If range metadata is attached to this call, set known bits from that,
1453 // and then intersect with known bits based on other properties of the
1456 Q.IIQ.getMetadata(cast<Instruction>(I), LLVMContext::MD_range))
1457 computeKnownBitsFromRangeMetadata(*MD, Known);
1458 if (const Value *RV = ImmutableCallSite(I).getReturnedArgOperand()) {
1459 computeKnownBits(RV, Known2, Depth + 1, Q);
1460 Known.Zero |= Known2.Zero;
1461 Known.One |= Known2.One;
1463 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
1464 switch (II->getIntrinsicID()) {
1466 case Intrinsic::bitreverse:
1467 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1468 Known.Zero |= Known2.Zero.reverseBits();
1469 Known.One |= Known2.One.reverseBits();
1471 case Intrinsic::bswap:
1472 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1473 Known.Zero |= Known2.Zero.byteSwap();
1474 Known.One |= Known2.One.byteSwap();
1476 case Intrinsic::ctlz: {
1477 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1478 // If we have a known 1, its position is our upper bound.
1479 unsigned PossibleLZ = Known2.One.countLeadingZeros();
1480 // If this call is undefined for 0, the result will be less than 2^n.
1481 if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
1482 PossibleLZ = std::min(PossibleLZ, BitWidth - 1);
1483 unsigned LowBits = Log2_32(PossibleLZ)+1;
1484 Known.Zero.setBitsFrom(LowBits);
1487 case Intrinsic::cttz: {
1488 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1489 // If we have a known 1, its position is our upper bound.
1490 unsigned PossibleTZ = Known2.One.countTrailingZeros();
1491 // If this call is undefined for 0, the result will be less than 2^n.
1492 if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
1493 PossibleTZ = std::min(PossibleTZ, BitWidth - 1);
1494 unsigned LowBits = Log2_32(PossibleTZ)+1;
1495 Known.Zero.setBitsFrom(LowBits);
1498 case Intrinsic::ctpop: {
1499 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1500 // We can bound the space the count needs. Also, bits known to be zero
1501 // can't contribute to the population.
1502 unsigned BitsPossiblySet = Known2.countMaxPopulation();
1503 unsigned LowBits = Log2_32(BitsPossiblySet)+1;
1504 Known.Zero.setBitsFrom(LowBits);
1505 // TODO: we could bound KnownOne using the lower bound on the number
1506 // of bits which might be set provided by popcnt KnownOne2.
1509 case Intrinsic::fshr:
1510 case Intrinsic::fshl: {
1512 if (!match(I->getOperand(2), m_APInt(SA)))
1515 // Normalize to funnel shift left.
1516 uint64_t ShiftAmt = SA->urem(BitWidth);
1517 if (II->getIntrinsicID() == Intrinsic::fshr)
1518 ShiftAmt = BitWidth - ShiftAmt;
1520 KnownBits Known3(Known);
1521 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1522 computeKnownBits(I->getOperand(1), Known3, Depth + 1, Q);
1525 Known2.Zero.shl(ShiftAmt) | Known3.Zero.lshr(BitWidth - ShiftAmt);
1527 Known2.One.shl(ShiftAmt) | Known3.One.lshr(BitWidth - ShiftAmt);
1530 case Intrinsic::x86_sse42_crc32_64_64:
1531 Known.Zero.setBitsFrom(32);
1536 case Instruction::ExtractElement:
1537 // Look through extract element. At the moment we keep this simple and skip
1538 // tracking the specific element. But at least we might find information
1539 // valid for all elements of the vector (for example if vector is sign
1540 // extended, shifted, etc).
1541 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1543 case Instruction::ExtractValue:
1544 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) {
1545 const ExtractValueInst *EVI = cast<ExtractValueInst>(I);
1546 if (EVI->getNumIndices() != 1) break;
1547 if (EVI->getIndices()[0] == 0) {
1548 switch (II->getIntrinsicID()) {
1550 case Intrinsic::uadd_with_overflow:
1551 case Intrinsic::sadd_with_overflow:
1552 computeKnownBitsAddSub(true, II->getArgOperand(0),
1553 II->getArgOperand(1), false, Known, Known2,
1556 case Intrinsic::usub_with_overflow:
1557 case Intrinsic::ssub_with_overflow:
1558 computeKnownBitsAddSub(false, II->getArgOperand(0),
1559 II->getArgOperand(1), false, Known, Known2,
1562 case Intrinsic::umul_with_overflow:
1563 case Intrinsic::smul_with_overflow:
1564 computeKnownBitsMul(II->getArgOperand(0), II->getArgOperand(1), false,
1565 Known, Known2, Depth, Q);
1573 /// Determine which bits of V are known to be either zero or one and return
1575 KnownBits computeKnownBits(const Value *V, unsigned Depth, const Query &Q) {
1576 KnownBits Known(getBitWidth(V->getType(), Q.DL));
1577 computeKnownBits(V, Known, Depth, Q);
1581 /// Determine which bits of V are known to be either zero or one and return
1582 /// them in the Known bit set.
1584 /// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
1585 /// we cannot optimize based on the assumption that it is zero without changing
1586 /// it to be an explicit zero. If we don't change it to zero, other code could
1587 /// optimized based on the contradictory assumption that it is non-zero.
1588 /// Because instcombine aggressively folds operations with undef args anyway,
1589 /// this won't lose us code quality.
1591 /// This function is defined on values with integer type, values with pointer
1592 /// type, and vectors of integers. In the case
1593 /// where V is a vector, known zero, and known one values are the
1594 /// same width as the vector element, and the bit is set only if it is true
1595 /// for all of the elements in the vector.
1596 void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
1598 assert(V && "No Value?");
1599 assert(Depth <= MaxDepth && "Limit Search Depth");
1600 unsigned BitWidth = Known.getBitWidth();
1602 assert((V->getType()->isIntOrIntVectorTy(BitWidth) ||
1603 V->getType()->isPtrOrPtrVectorTy()) &&
1604 "Not integer or pointer type!");
1606 Type *ScalarTy = V->getType()->getScalarType();
1607 unsigned ExpectedWidth = ScalarTy->isPointerTy() ?
1608 Q.DL.getIndexTypeSizeInBits(ScalarTy) : Q.DL.getTypeSizeInBits(ScalarTy);
1609 assert(ExpectedWidth == BitWidth && "V and Known should have same BitWidth");
1611 (void)ExpectedWidth;
1614 if (match(V, m_APInt(C))) {
1615 // We know all of the bits for a scalar constant or a splat vector constant!
1617 Known.Zero = ~Known.One;
1620 // Null and aggregate-zero are all-zeros.
1621 if (isa<ConstantPointerNull>(V) || isa<ConstantAggregateZero>(V)) {
1625 // Handle a constant vector by taking the intersection of the known bits of
1627 if (const ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(V)) {
1628 // We know that CDS must be a vector of integers. Take the intersection of
1630 Known.Zero.setAllBits(); Known.One.setAllBits();
1631 for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
1632 APInt Elt = CDS->getElementAsAPInt(i);
1639 if (const auto *CV = dyn_cast<ConstantVector>(V)) {
1640 // We know that CV must be a vector of integers. Take the intersection of
1642 Known.Zero.setAllBits(); Known.One.setAllBits();
1643 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
1644 Constant *Element = CV->getAggregateElement(i);
1645 auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
1650 const APInt &Elt = ElementCI->getValue();
1657 // Start out not knowing anything.
1660 // We can't imply anything about undefs.
1661 if (isa<UndefValue>(V))
1664 // There's no point in looking through other users of ConstantData for
1665 // assumptions. Confirm that we've handled them all.
1666 assert(!isa<ConstantData>(V) && "Unhandled constant data!");
1668 // Limit search depth.
1669 // All recursive calls that increase depth must come after this.
1670 if (Depth == MaxDepth)
1673 // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
1674 // the bits of its aliasee.
1675 if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
1676 if (!GA->isInterposable())
1677 computeKnownBits(GA->getAliasee(), Known, Depth + 1, Q);
1681 if (const Operator *I = dyn_cast<Operator>(V))
1682 computeKnownBitsFromOperator(I, Known, Depth, Q);
1684 // Aligned pointers have trailing zeros - refine Known.Zero set
1685 if (V->getType()->isPointerTy()) {
1686 unsigned Align = V->getPointerAlignment(Q.DL);
1688 Known.Zero.setLowBits(countTrailingZeros(Align));
1691 // computeKnownBitsFromAssume strictly refines Known.
1692 // Therefore, we run them after computeKnownBitsFromOperator.
1694 // Check whether a nearby assume intrinsic can determine some known bits.
1695 computeKnownBitsFromAssume(V, Known, Depth, Q);
1697 assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?");
1700 /// Return true if the given value is known to have exactly one
1701 /// bit set when defined. For vectors return true if every element is known to
1702 /// be a power of two when defined. Supports values with integer or pointer
1703 /// types and vectors of integers.
1704 bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
1706 assert(Depth <= MaxDepth && "Limit Search Depth");
1708 // Attempt to match against constants.
1709 if (OrZero && match(V, m_Power2OrZero()))
1711 if (match(V, m_Power2()))
1714 // 1 << X is clearly a power of two if the one is not shifted off the end. If
1715 // it is shifted off the end then the result is undefined.
1716 if (match(V, m_Shl(m_One(), m_Value())))
1719 // (signmask) >>l X is clearly a power of two if the one is not shifted off
1720 // the bottom. If it is shifted off the bottom then the result is undefined.
1721 if (match(V, m_LShr(m_SignMask(), m_Value())))
1724 // The remaining tests are all recursive, so bail out if we hit the limit.
1725 if (Depth++ == MaxDepth)
1728 Value *X = nullptr, *Y = nullptr;
1729 // A shift left or a logical shift right of a power of two is a power of two
1731 if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
1732 match(V, m_LShr(m_Value(X), m_Value()))))
1733 return isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q);
1735 if (const ZExtInst *ZI = dyn_cast<ZExtInst>(V))
1736 return isKnownToBeAPowerOfTwo(ZI->getOperand(0), OrZero, Depth, Q);
1738 if (const SelectInst *SI = dyn_cast<SelectInst>(V))
1739 return isKnownToBeAPowerOfTwo(SI->getTrueValue(), OrZero, Depth, Q) &&
1740 isKnownToBeAPowerOfTwo(SI->getFalseValue(), OrZero, Depth, Q);
1742 if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
1743 // A power of two and'd with anything is a power of two or zero.
1744 if (isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q) ||
1745 isKnownToBeAPowerOfTwo(Y, /*OrZero*/ true, Depth, Q))
1747 // X & (-X) is always a power of two or zero.
1748 if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X))))
1753 // Adding a power-of-two or zero to the same power-of-two or zero yields
1754 // either the original power-of-two, a larger power-of-two or zero.
1755 if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
1756 const OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V);
1757 if (OrZero || Q.IIQ.hasNoUnsignedWrap(VOBO) ||
1758 Q.IIQ.hasNoSignedWrap(VOBO)) {
1759 if (match(X, m_And(m_Specific(Y), m_Value())) ||
1760 match(X, m_And(m_Value(), m_Specific(Y))))
1761 if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth, Q))
1763 if (match(Y, m_And(m_Specific(X), m_Value())) ||
1764 match(Y, m_And(m_Value(), m_Specific(X))))
1765 if (isKnownToBeAPowerOfTwo(X, OrZero, Depth, Q))
1768 unsigned BitWidth = V->getType()->getScalarSizeInBits();
1769 KnownBits LHSBits(BitWidth);
1770 computeKnownBits(X, LHSBits, Depth, Q);
1772 KnownBits RHSBits(BitWidth);
1773 computeKnownBits(Y, RHSBits, Depth, Q);
1774 // If i8 V is a power of two or zero:
1775 // ZeroBits: 1 1 1 0 1 1 1 1
1776 // ~ZeroBits: 0 0 0 1 0 0 0 0
1777 if ((~(LHSBits.Zero & RHSBits.Zero)).isPowerOf2())
1778 // If OrZero isn't set, we cannot give back a zero result.
1779 // Make sure either the LHS or RHS has a bit set.
1780 if (OrZero || RHSBits.One.getBoolValue() || LHSBits.One.getBoolValue())
1785 // An exact divide or right shift can only shift off zero bits, so the result
1786 // is a power of two only if the first operand is a power of two and not
1787 // copying a sign bit (sdiv int_min, 2).
1788 if (match(V, m_Exact(m_LShr(m_Value(), m_Value()))) ||
1789 match(V, m_Exact(m_UDiv(m_Value(), m_Value())))) {
1790 return isKnownToBeAPowerOfTwo(cast<Operator>(V)->getOperand(0), OrZero,
1797 /// Test whether a GEP's result is known to be non-null.
1799 /// Uses properties inherent in a GEP to try to determine whether it is known
1802 /// Currently this routine does not support vector GEPs.
1803 static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
1805 const Function *F = nullptr;
1806 if (const Instruction *I = dyn_cast<Instruction>(GEP))
1807 F = I->getFunction();
1809 if (!GEP->isInBounds() ||
1810 NullPointerIsDefined(F, GEP->getPointerAddressSpace()))
1813 // FIXME: Support vector-GEPs.
1814 assert(GEP->getType()->isPointerTy() && "We only support plain pointer GEP");
1816 // If the base pointer is non-null, we cannot walk to a null address with an
1817 // inbounds GEP in address space zero.
1818 if (isKnownNonZero(GEP->getPointerOperand(), Depth, Q))
1821 // Walk the GEP operands and see if any operand introduces a non-zero offset.
1822 // If so, then the GEP cannot produce a null pointer, as doing so would
1823 // inherently violate the inbounds contract within address space zero.
1824 for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
1825 GTI != GTE; ++GTI) {
1826 // Struct types are easy -- they must always be indexed by a constant.
1827 if (StructType *STy = GTI.getStructTypeOrNull()) {
1828 ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
1829 unsigned ElementIdx = OpC->getZExtValue();
1830 const StructLayout *SL = Q.DL.getStructLayout(STy);
1831 uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
1832 if (ElementOffset > 0)
1837 // If we have a zero-sized type, the index doesn't matter. Keep looping.
1838 if (Q.DL.getTypeAllocSize(GTI.getIndexedType()) == 0)
1841 // Fast path the constant operand case both for efficiency and so we don't
1842 // increment Depth when just zipping down an all-constant GEP.
1843 if (ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand())) {
1849 // We post-increment Depth here because while isKnownNonZero increments it
1850 // as well, when we pop back up that increment won't persist. We don't want
1851 // to recurse 10k times just because we have 10k GEP operands. We don't
1852 // bail completely out because we want to handle constant GEPs regardless
1854 if (Depth++ >= MaxDepth)
1857 if (isKnownNonZero(GTI.getOperand(), Depth, Q))
1864 static bool isKnownNonNullFromDominatingCondition(const Value *V,
1865 const Instruction *CtxI,
1866 const DominatorTree *DT) {
1867 assert(V->getType()->isPointerTy() && "V must be pointer type");
1868 assert(!isa<ConstantData>(V) && "Did not expect ConstantPointerNull");
1873 unsigned NumUsesExplored = 0;
1874 for (auto *U : V->users()) {
1875 // Avoid massive lists
1876 if (NumUsesExplored >= DomConditionsMaxUses)
1880 // If the value is used as an argument to a call or invoke, then argument
1881 // attributes may provide an answer about null-ness.
1882 if (auto CS = ImmutableCallSite(U))
1883 if (auto *CalledFunc = CS.getCalledFunction())
1884 for (const Argument &Arg : CalledFunc->args())
1885 if (CS.getArgOperand(Arg.getArgNo()) == V &&
1886 Arg.hasNonNullAttr() && DT->dominates(CS.getInstruction(), CtxI))
1889 // Consider only compare instructions uniquely controlling a branch
1890 CmpInst::Predicate Pred;
1891 if (!match(const_cast<User *>(U),
1892 m_c_ICmp(Pred, m_Specific(V), m_Zero())) ||
1893 (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE))
1896 SmallVector<const User *, 4> WorkList;
1897 SmallPtrSet<const User *, 4> Visited;
1898 for (auto *CmpU : U->users()) {
1899 assert(WorkList.empty() && "Should be!");
1900 if (Visited.insert(CmpU).second)
1901 WorkList.push_back(CmpU);
1903 while (!WorkList.empty()) {
1904 auto *Curr = WorkList.pop_back_val();
1906 // If a user is an AND, add all its users to the work list. We only
1907 // propagate "pred != null" condition through AND because it is only
1908 // correct to assume that all conditions of AND are met in true branch.
1909 // TODO: Support similar logic of OR and EQ predicate?
1910 if (Pred == ICmpInst::ICMP_NE)
1911 if (auto *BO = dyn_cast<BinaryOperator>(Curr))
1912 if (BO->getOpcode() == Instruction::And) {
1913 for (auto *BOU : BO->users())
1914 if (Visited.insert(BOU).second)
1915 WorkList.push_back(BOU);
1919 if (const BranchInst *BI = dyn_cast<BranchInst>(Curr)) {
1920 assert(BI->isConditional() && "uses a comparison!");
1922 BasicBlock *NonNullSuccessor =
1923 BI->getSuccessor(Pred == ICmpInst::ICMP_EQ ? 1 : 0);
1924 BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
1925 if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
1927 } else if (Pred == ICmpInst::ICMP_NE && isGuard(Curr) &&
1928 DT->dominates(cast<Instruction>(Curr), CtxI)) {
1938 /// Does the 'Range' metadata (which must be a valid MD_range operand list)
1939 /// ensure that the value it's attached to is never Value? 'RangeType' is
1940 /// is the type of the value described by the range.
1941 static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value) {
1942 const unsigned NumRanges = Ranges->getNumOperands() / 2;
1943 assert(NumRanges >= 1);
1944 for (unsigned i = 0; i < NumRanges; ++i) {
1945 ConstantInt *Lower =
1946 mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 0));
1947 ConstantInt *Upper =
1948 mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 1));
1949 ConstantRange Range(Lower->getValue(), Upper->getValue());
1950 if (Range.contains(Value))
1956 /// Return true if the given value is known to be non-zero when defined. For
1957 /// vectors, return true if every element is known to be non-zero when
1958 /// defined. For pointers, if the context instruction and dominator tree are
1959 /// specified, perform context-sensitive analysis and return true if the
1960 /// pointer couldn't possibly be null at the specified instruction.
1961 /// Supports values with integer or pointer type and vectors of integers.
1962 bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q) {
1963 if (auto *C = dyn_cast<Constant>(V)) {
1964 if (C->isNullValue())
1966 if (isa<ConstantInt>(C))
1967 // Must be non-zero due to null test above.
1970 // For constant vectors, check that all elements are undefined or known
1971 // non-zero to determine that the whole vector is known non-zero.
1972 if (auto *VecTy = dyn_cast<VectorType>(C->getType())) {
1973 for (unsigned i = 0, e = VecTy->getNumElements(); i != e; ++i) {
1974 Constant *Elt = C->getAggregateElement(i);
1975 if (!Elt || Elt->isNullValue())
1977 if (!isa<UndefValue>(Elt) && !isa<ConstantInt>(Elt))
1983 // A global variable in address space 0 is non null unless extern weak
1984 // or an absolute symbol reference. Other address spaces may have null as a
1985 // valid address for a global, so we can't assume anything.
1986 if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
1987 if (!GV->isAbsoluteSymbolRef() && !GV->hasExternalWeakLinkage() &&
1988 GV->getType()->getAddressSpace() == 0)
1994 if (auto *I = dyn_cast<Instruction>(V)) {
1995 if (MDNode *Ranges = Q.IIQ.getMetadata(I, LLVMContext::MD_range)) {
1996 // If the possible ranges don't contain zero, then the value is
1997 // definitely non-zero.
1998 if (auto *Ty = dyn_cast<IntegerType>(V->getType())) {
1999 const APInt ZeroValue(Ty->getBitWidth(), 0);
2000 if (rangeMetadataExcludesValue(Ranges, ZeroValue))
2006 // Some of the tests below are recursive, so bail out if we hit the limit.
2007 if (Depth++ >= MaxDepth)
2010 // Check for pointer simplifications.
2011 if (V->getType()->isPointerTy()) {
2012 // Alloca never returns null, malloc might.
2013 if (isa<AllocaInst>(V) && Q.DL.getAllocaAddrSpace() == 0)
2016 // A byval, inalloca, or nonnull argument is never null.
2017 if (const Argument *A = dyn_cast<Argument>(V))
2018 if (A->hasByValOrInAllocaAttr() || A->hasNonNullAttr())
2021 // A Load tagged with nonnull metadata is never null.
2022 if (const LoadInst *LI = dyn_cast<LoadInst>(V))
2023 if (Q.IIQ.getMetadata(LI, LLVMContext::MD_nonnull))
2026 if (const auto *Call = dyn_cast<CallBase>(V)) {
2027 if (Call->isReturnNonNull())
2029 if (const auto *RP = getArgumentAliasingToReturnedPointer(Call))
2030 return isKnownNonZero(RP, Depth, Q);
2035 // Check for recursive pointer simplifications.
2036 if (V->getType()->isPointerTy()) {
2037 if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
2040 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V))
2041 if (isGEPKnownNonNull(GEP, Depth, Q))
2045 unsigned BitWidth = getBitWidth(V->getType()->getScalarType(), Q.DL);
2047 // X | Y != 0 if X != 0 or Y != 0.
2048 Value *X = nullptr, *Y = nullptr;
2049 if (match(V, m_Or(m_Value(X), m_Value(Y))))
2050 return isKnownNonZero(X, Depth, Q) || isKnownNonZero(Y, Depth, Q);
2052 // ext X != 0 if X != 0.
2053 if (isa<SExtInst>(V) || isa<ZExtInst>(V))
2054 return isKnownNonZero(cast<Instruction>(V)->getOperand(0), Depth, Q);
2056 // shl X, Y != 0 if X is odd. Note that the value of the shift is undefined
2057 // if the lowest bit is shifted off the end.
2058 if (match(V, m_Shl(m_Value(X), m_Value(Y)))) {
2059 // shl nuw can't remove any non-zero bits.
2060 const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
2061 if (Q.IIQ.hasNoUnsignedWrap(BO))
2062 return isKnownNonZero(X, Depth, Q);
2064 KnownBits Known(BitWidth);
2065 computeKnownBits(X, Known, Depth, Q);
2069 // shr X, Y != 0 if X is negative. Note that the value of the shift is not
2070 // defined if the sign bit is shifted off the end.
2071 else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) {
2072 // shr exact can only shift out zero bits.
2073 const PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
2075 return isKnownNonZero(X, Depth, Q);
2077 KnownBits Known = computeKnownBits(X, Depth, Q);
2078 if (Known.isNegative())
2081 // If the shifter operand is a constant, and all of the bits shifted
2082 // out are known to be zero, and X is known non-zero then at least one
2083 // non-zero bit must remain.
2084 if (ConstantInt *Shift = dyn_cast<ConstantInt>(Y)) {
2085 auto ShiftVal = Shift->getLimitedValue(BitWidth - 1);
2086 // Is there a known one in the portion not shifted out?
2087 if (Known.countMaxLeadingZeros() < BitWidth - ShiftVal)
2089 // Are all the bits to be shifted out known zero?
2090 if (Known.countMinTrailingZeros() >= ShiftVal)
2091 return isKnownNonZero(X, Depth, Q);
2094 // div exact can only produce a zero if the dividend is zero.
2095 else if (match(V, m_Exact(m_IDiv(m_Value(X), m_Value())))) {
2096 return isKnownNonZero(X, Depth, Q);
2099 else if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
2100 KnownBits XKnown = computeKnownBits(X, Depth, Q);
2101 KnownBits YKnown = computeKnownBits(Y, Depth, Q);
2103 // If X and Y are both non-negative (as signed values) then their sum is not
2104 // zero unless both X and Y are zero.
2105 if (XKnown.isNonNegative() && YKnown.isNonNegative())
2106 if (isKnownNonZero(X, Depth, Q) || isKnownNonZero(Y, Depth, Q))
2109 // If X and Y are both negative (as signed values) then their sum is not
2110 // zero unless both X and Y equal INT_MIN.
2111 if (XKnown.isNegative() && YKnown.isNegative()) {
2112 APInt Mask = APInt::getSignedMaxValue(BitWidth);
2113 // The sign bit of X is set. If some other bit is set then X is not equal
2115 if (XKnown.One.intersects(Mask))
2117 // The sign bit of Y is set. If some other bit is set then Y is not equal
2119 if (YKnown.One.intersects(Mask))
2123 // The sum of a non-negative number and a power of two is not zero.
2124 if (XKnown.isNonNegative() &&
2125 isKnownToBeAPowerOfTwo(Y, /*OrZero*/ false, Depth, Q))
2127 if (YKnown.isNonNegative() &&
2128 isKnownToBeAPowerOfTwo(X, /*OrZero*/ false, Depth, Q))
2132 else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) {
2133 const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
2134 // If X and Y are non-zero then so is X * Y as long as the multiplication
2135 // does not overflow.
2136 if ((Q.IIQ.hasNoSignedWrap(BO) || Q.IIQ.hasNoUnsignedWrap(BO)) &&
2137 isKnownNonZero(X, Depth, Q) && isKnownNonZero(Y, Depth, Q))
2140 // (C ? X : Y) != 0 if X != 0 and Y != 0.
2141 else if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
2142 if (isKnownNonZero(SI->getTrueValue(), Depth, Q) &&
2143 isKnownNonZero(SI->getFalseValue(), Depth, Q))
2147 else if (const PHINode *PN = dyn_cast<PHINode>(V)) {
2148 // Try and detect a recurrence that monotonically increases from a
2149 // starting value, as these are common as induction variables.
2150 if (PN->getNumIncomingValues() == 2) {
2151 Value *Start = PN->getIncomingValue(0);
2152 Value *Induction = PN->getIncomingValue(1);
2153 if (isa<ConstantInt>(Induction) && !isa<ConstantInt>(Start))
2154 std::swap(Start, Induction);
2155 if (ConstantInt *C = dyn_cast<ConstantInt>(Start)) {
2156 if (!C->isZero() && !C->isNegative()) {
2158 if (Q.IIQ.UseInstrInfo &&
2159 (match(Induction, m_NSWAdd(m_Specific(PN), m_ConstantInt(X))) ||
2160 match(Induction, m_NUWAdd(m_Specific(PN), m_ConstantInt(X)))) &&
2166 // Check if all incoming values are non-zero constant.
2167 bool AllNonZeroConstants = llvm::all_of(PN->operands(), [](Value *V) {
2168 return isa<ConstantInt>(V) && !cast<ConstantInt>(V)->isZero();
2170 if (AllNonZeroConstants)
2174 KnownBits Known(BitWidth);
2175 computeKnownBits(V, Known, Depth, Q);
2176 return Known.One != 0;
2179 /// Return true if V2 == V1 + X, where X is known non-zero.
2180 static bool isAddOfNonZero(const Value *V1, const Value *V2, const Query &Q) {
2181 const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
2182 if (!BO || BO->getOpcode() != Instruction::Add)
2184 Value *Op = nullptr;
2185 if (V2 == BO->getOperand(0))
2186 Op = BO->getOperand(1);
2187 else if (V2 == BO->getOperand(1))
2188 Op = BO->getOperand(0);
2191 return isKnownNonZero(Op, 0, Q);
2194 /// Return true if it is known that V1 != V2.
2195 static bool isKnownNonEqual(const Value *V1, const Value *V2, const Query &Q) {
2198 if (V1->getType() != V2->getType())
2199 // We can't look through casts yet.
2201 if (isAddOfNonZero(V1, V2, Q) || isAddOfNonZero(V2, V1, Q))
2204 if (V1->getType()->isIntOrIntVectorTy()) {
2205 // Are any known bits in V1 contradictory to known bits in V2? If V1
2206 // has a known zero where V2 has a known one, they must not be equal.
2207 KnownBits Known1 = computeKnownBits(V1, 0, Q);
2208 KnownBits Known2 = computeKnownBits(V2, 0, Q);
2210 if (Known1.Zero.intersects(Known2.One) ||
2211 Known2.Zero.intersects(Known1.One))
2217 /// Return true if 'V & Mask' is known to be zero. We use this predicate to
2218 /// simplify operations downstream. Mask is known to be zero for bits that V
2221 /// This function is defined on values with integer type, values with pointer
2222 /// type, and vectors of integers. In the case
2223 /// where V is a vector, the mask, known zero, and known one values are the
2224 /// same width as the vector element, and the bit is set only if it is true
2225 /// for all of the elements in the vector.
2226 bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
2228 KnownBits Known(Mask.getBitWidth());
2229 computeKnownBits(V, Known, Depth, Q);
2230 return Mask.isSubsetOf(Known.Zero);
2233 // Match a signed min+max clamp pattern like smax(smin(In, CHigh), CLow).
2234 // Returns the input and lower/upper bounds.
2235 static bool isSignedMinMaxClamp(const Value *Select, const Value *&In,
2236 const APInt *&CLow, const APInt *&CHigh) {
2237 assert(isa<Operator>(Select) &&
2238 cast<Operator>(Select)->getOpcode() == Instruction::Select &&
2239 "Input should be a Select!");
2241 const Value *LHS, *RHS, *LHS2, *RHS2;
2242 SelectPatternFlavor SPF = matchSelectPattern(Select, LHS, RHS).Flavor;
2243 if (SPF != SPF_SMAX && SPF != SPF_SMIN)
2246 if (!match(RHS, m_APInt(CLow)))
2249 SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor;
2250 if (getInverseMinMaxFlavor(SPF) != SPF2)
2253 if (!match(RHS2, m_APInt(CHigh)))
2256 if (SPF == SPF_SMIN)
2257 std::swap(CLow, CHigh);
2260 return CLow->sle(*CHigh);
2263 /// For vector constants, loop over the elements and find the constant with the
2264 /// minimum number of sign bits. Return 0 if the value is not a vector constant
2265 /// or if any element was not analyzed; otherwise, return the count for the
2266 /// element with the minimum number of sign bits.
2267 static unsigned computeNumSignBitsVectorConstant(const Value *V,
2269 const auto *CV = dyn_cast<Constant>(V);
2270 if (!CV || !CV->getType()->isVectorTy())
2273 unsigned MinSignBits = TyBits;
2274 unsigned NumElts = CV->getType()->getVectorNumElements();
2275 for (unsigned i = 0; i != NumElts; ++i) {
2276 // If we find a non-ConstantInt, bail out.
2277 auto *Elt = dyn_cast_or_null<ConstantInt>(CV->getAggregateElement(i));
2281 MinSignBits = std::min(MinSignBits, Elt->getValue().getNumSignBits());
2287 static unsigned ComputeNumSignBitsImpl(const Value *V, unsigned Depth,
2290 static unsigned ComputeNumSignBits(const Value *V, unsigned Depth,
2292 unsigned Result = ComputeNumSignBitsImpl(V, Depth, Q);
2293 assert(Result > 0 && "At least one sign bit needs to be present!");
2297 /// Return the number of times the sign bit of the register is replicated into
2298 /// the other bits. We know that at least 1 bit is always equal to the sign bit
2299 /// (itself), but other cases can give us information. For example, immediately
2300 /// after an "ashr X, 2", we know that the top 3 bits are all equal to each
2301 /// other, so we return 3. For vectors, return the number of sign bits for the
2302 /// vector element with the minimum number of known sign bits.
2303 static unsigned ComputeNumSignBitsImpl(const Value *V, unsigned Depth,
2305 assert(Depth <= MaxDepth && "Limit Search Depth");
2307 // We return the minimum number of sign bits that are guaranteed to be present
2308 // in V, so for undef we have to conservatively return 1. We don't have the
2309 // same behavior for poison though -- that's a FIXME today.
2311 Type *ScalarTy = V->getType()->getScalarType();
2312 unsigned TyBits = ScalarTy->isPointerTy() ?
2313 Q.DL.getIndexTypeSizeInBits(ScalarTy) :
2314 Q.DL.getTypeSizeInBits(ScalarTy);
2317 unsigned FirstAnswer = 1;
2319 // Note that ConstantInt is handled by the general computeKnownBits case
2322 if (Depth == MaxDepth)
2323 return 1; // Limit search depth.
2325 const Operator *U = dyn_cast<Operator>(V);
2326 switch (Operator::getOpcode(V)) {
2328 case Instruction::SExt:
2329 Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits();
2330 return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q) + Tmp;
2332 case Instruction::SDiv: {
2333 const APInt *Denominator;
2334 // sdiv X, C -> adds log(C) sign bits.
2335 if (match(U->getOperand(1), m_APInt(Denominator))) {
2337 // Ignore non-positive denominator.
2338 if (!Denominator->isStrictlyPositive())
2341 // Calculate the incoming numerator bits.
2342 unsigned NumBits = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2344 // Add floor(log(C)) bits to the numerator bits.
2345 return std::min(TyBits, NumBits + Denominator->logBase2());
2350 case Instruction::SRem: {
2351 const APInt *Denominator;
2352 // srem X, C -> we know that the result is within [-C+1,C) when C is a
2353 // positive constant. This let us put a lower bound on the number of sign
2355 if (match(U->getOperand(1), m_APInt(Denominator))) {
2357 // Ignore non-positive denominator.
2358 if (!Denominator->isStrictlyPositive())
2361 // Calculate the incoming numerator bits. SRem by a positive constant
2362 // can't lower the number of sign bits.
2364 ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2366 // Calculate the leading sign bit constraints by examining the
2367 // denominator. Given that the denominator is positive, there are two
2370 // 1. the numerator is positive. The result range is [0,C) and [0,C) u<
2371 // (1 << ceilLogBase2(C)).
2373 // 2. the numerator is negative. Then the result range is (-C,0] and
2374 // integers in (-C,0] are either 0 or >u (-1 << ceilLogBase2(C)).
2376 // Thus a lower bound on the number of sign bits is `TyBits -
2377 // ceilLogBase2(C)`.
2379 unsigned ResBits = TyBits - Denominator->ceilLogBase2();
2380 return std::max(NumrBits, ResBits);
2385 case Instruction::AShr: {
2386 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2387 // ashr X, C -> adds C sign bits. Vectors too.
2389 if (match(U->getOperand(1), m_APInt(ShAmt))) {
2390 if (ShAmt->uge(TyBits))
2391 break; // Bad shift.
2392 unsigned ShAmtLimited = ShAmt->getZExtValue();
2393 Tmp += ShAmtLimited;
2394 if (Tmp > TyBits) Tmp = TyBits;
2398 case Instruction::Shl: {
2400 if (match(U->getOperand(1), m_APInt(ShAmt))) {
2401 // shl destroys sign bits.
2402 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2403 if (ShAmt->uge(TyBits) || // Bad shift.
2404 ShAmt->uge(Tmp)) break; // Shifted all sign bits out.
2405 Tmp2 = ShAmt->getZExtValue();
2410 case Instruction::And:
2411 case Instruction::Or:
2412 case Instruction::Xor: // NOT is handled here.
2413 // Logical binary ops preserve the number of sign bits at the worst.
2414 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2416 Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2417 FirstAnswer = std::min(Tmp, Tmp2);
2418 // We computed what we know about the sign bits as our first
2419 // answer. Now proceed to the generic code that uses
2420 // computeKnownBits, and pick whichever answer is better.
2424 case Instruction::Select: {
2425 // If we have a clamp pattern, we know that the number of sign bits will be
2426 // the minimum of the clamp min/max range.
2428 const APInt *CLow, *CHigh;
2429 if (isSignedMinMaxClamp(U, X, CLow, CHigh))
2430 return std::min(CLow->getNumSignBits(), CHigh->getNumSignBits());
2432 Tmp = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2433 if (Tmp == 1) break;
2434 Tmp2 = ComputeNumSignBits(U->getOperand(2), Depth + 1, Q);
2435 return std::min(Tmp, Tmp2);
2438 case Instruction::Add:
2439 // Add can have at most one carry bit. Thus we know that the output
2440 // is, at worst, one more bit than the inputs.
2441 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2442 if (Tmp == 1) break;
2444 // Special case decrementing a value (ADD X, -1):
2445 if (const auto *CRHS = dyn_cast<Constant>(U->getOperand(1)))
2446 if (CRHS->isAllOnesValue()) {
2447 KnownBits Known(TyBits);
2448 computeKnownBits(U->getOperand(0), Known, Depth + 1, Q);
2450 // If the input is known to be 0 or 1, the output is 0/-1, which is all
2452 if ((Known.Zero | 1).isAllOnesValue())
2455 // If we are subtracting one from a positive number, there is no carry
2456 // out of the result.
2457 if (Known.isNonNegative())
2461 Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2462 if (Tmp2 == 1) break;
2463 return std::min(Tmp, Tmp2)-1;
2465 case Instruction::Sub:
2466 Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2467 if (Tmp2 == 1) break;
2470 if (const auto *CLHS = dyn_cast<Constant>(U->getOperand(0)))
2471 if (CLHS->isNullValue()) {
2472 KnownBits Known(TyBits);
2473 computeKnownBits(U->getOperand(1), Known, Depth + 1, Q);
2474 // If the input is known to be 0 or 1, the output is 0/-1, which is all
2476 if ((Known.Zero | 1).isAllOnesValue())
2479 // If the input is known to be positive (the sign bit is known clear),
2480 // the output of the NEG has the same number of sign bits as the input.
2481 if (Known.isNonNegative())
2484 // Otherwise, we treat this like a SUB.
2487 // Sub can have at most one carry bit. Thus we know that the output
2488 // is, at worst, one more bit than the inputs.
2489 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2490 if (Tmp == 1) break;
2491 return std::min(Tmp, Tmp2)-1;
2493 case Instruction::Mul: {
2494 // The output of the Mul can be at most twice the valid bits in the inputs.
2495 unsigned SignBitsOp0 = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2496 if (SignBitsOp0 == 1) break;
2497 unsigned SignBitsOp1 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2498 if (SignBitsOp1 == 1) break;
2499 unsigned OutValidBits =
2500 (TyBits - SignBitsOp0 + 1) + (TyBits - SignBitsOp1 + 1);
2501 return OutValidBits > TyBits ? 1 : TyBits - OutValidBits + 1;
2504 case Instruction::PHI: {
2505 const PHINode *PN = cast<PHINode>(U);
2506 unsigned NumIncomingValues = PN->getNumIncomingValues();
2507 // Don't analyze large in-degree PHIs.
2508 if (NumIncomingValues > 4) break;
2509 // Unreachable blocks may have zero-operand PHI nodes.
2510 if (NumIncomingValues == 0) break;
2512 // Take the minimum of all incoming values. This can't infinitely loop
2513 // because of our depth threshold.
2514 Tmp = ComputeNumSignBits(PN->getIncomingValue(0), Depth + 1, Q);
2515 for (unsigned i = 1, e = NumIncomingValues; i != e; ++i) {
2516 if (Tmp == 1) return Tmp;
2518 Tmp, ComputeNumSignBits(PN->getIncomingValue(i), Depth + 1, Q));
2523 case Instruction::Trunc:
2524 // FIXME: it's tricky to do anything useful for this, but it is an important
2525 // case for targets like X86.
2528 case Instruction::ExtractElement:
2529 // Look through extract element. At the moment we keep this simple and skip
2530 // tracking the specific element. But at least we might find information
2531 // valid for all elements of the vector (for example if vector is sign
2532 // extended, shifted, etc).
2533 return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2535 case Instruction::ShuffleVector: {
2536 // TODO: This is copied almost directly from the SelectionDAG version of
2537 // ComputeNumSignBits. It would be better if we could share common
2538 // code. If not, make sure that changes are translated to the DAG.
2540 // Collect the minimum number of sign bits that are shared by every vector
2541 // element referenced by the shuffle.
2542 auto *Shuf = cast<ShuffleVectorInst>(U);
2543 int NumElts = Shuf->getOperand(0)->getType()->getVectorNumElements();
2544 int NumMaskElts = Shuf->getMask()->getType()->getVectorNumElements();
2545 APInt DemandedLHS(NumElts, 0), DemandedRHS(NumElts, 0);
2546 for (int i = 0; i != NumMaskElts; ++i) {
2547 int M = Shuf->getMaskValue(i);
2548 assert(M < NumElts * 2 && "Invalid shuffle mask constant");
2549 // For undef elements, we don't know anything about the common state of
2550 // the shuffle result.
2554 DemandedLHS.setBit(M % NumElts);
2556 DemandedRHS.setBit(M % NumElts);
2558 Tmp = std::numeric_limits<unsigned>::max();
2560 Tmp = ComputeNumSignBits(Shuf->getOperand(0), Depth + 1, Q);
2561 if (!!DemandedRHS) {
2562 Tmp2 = ComputeNumSignBits(Shuf->getOperand(1), Depth + 1, Q);
2563 Tmp = std::min(Tmp, Tmp2);
2565 // If we don't know anything, early out and try computeKnownBits fall-back.
2568 assert(Tmp <= V->getType()->getScalarSizeInBits() &&
2569 "Failed to determine minimum sign bits");
2574 // Finally, if we can prove that the top bits of the result are 0's or 1's,
2575 // use this information.
2577 // If we can examine all elements of a vector constant successfully, we're
2578 // done (we can't do any better than that). If not, keep trying.
2579 if (unsigned VecSignBits = computeNumSignBitsVectorConstant(V, TyBits))
2582 KnownBits Known(TyBits);
2583 computeKnownBits(V, Known, Depth, Q);
2585 // If we know that the sign bit is either zero or one, determine the number of
2586 // identical bits in the top of the input value.
2587 return std::max(FirstAnswer, Known.countMinSignBits());
2590 /// This function computes the integer multiple of Base that equals V.
2591 /// If successful, it returns true and returns the multiple in
2592 /// Multiple. If unsuccessful, it returns false. It looks
2593 /// through SExt instructions only if LookThroughSExt is true.
2594 bool llvm::ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
2595 bool LookThroughSExt, unsigned Depth) {
2596 const unsigned MaxDepth = 6;
2598 assert(V && "No Value?");
2599 assert(Depth <= MaxDepth && "Limit Search Depth");
2600 assert(V->getType()->isIntegerTy() && "Not integer or pointer type!");
2602 Type *T = V->getType();
2604 ConstantInt *CI = dyn_cast<ConstantInt>(V);
2614 ConstantExpr *CO = dyn_cast<ConstantExpr>(V);
2615 Constant *BaseVal = ConstantInt::get(T, Base);
2616 if (CO && CO == BaseVal) {
2618 Multiple = ConstantInt::get(T, 1);
2622 if (CI && CI->getZExtValue() % Base == 0) {
2623 Multiple = ConstantInt::get(T, CI->getZExtValue() / Base);
2627 if (Depth == MaxDepth) return false; // Limit search depth.
2629 Operator *I = dyn_cast<Operator>(V);
2630 if (!I) return false;
2632 switch (I->getOpcode()) {
2634 case Instruction::SExt:
2635 if (!LookThroughSExt) return false;
2636 // otherwise fall through to ZExt
2638 case Instruction::ZExt:
2639 return ComputeMultiple(I->getOperand(0), Base, Multiple,
2640 LookThroughSExt, Depth+1);
2641 case Instruction::Shl:
2642 case Instruction::Mul: {
2643 Value *Op0 = I->getOperand(0);
2644 Value *Op1 = I->getOperand(1);
2646 if (I->getOpcode() == Instruction::Shl) {
2647 ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1);
2648 if (!Op1CI) return false;
2649 // Turn Op0 << Op1 into Op0 * 2^Op1
2650 APInt Op1Int = Op1CI->getValue();
2651 uint64_t BitToSet = Op1Int.getLimitedValue(Op1Int.getBitWidth() - 1);
2652 APInt API(Op1Int.getBitWidth(), 0);
2653 API.setBit(BitToSet);
2654 Op1 = ConstantInt::get(V->getContext(), API);
2657 Value *Mul0 = nullptr;
2658 if (ComputeMultiple(Op0, Base, Mul0, LookThroughSExt, Depth+1)) {
2659 if (Constant *Op1C = dyn_cast<Constant>(Op1))
2660 if (Constant *MulC = dyn_cast<Constant>(Mul0)) {
2661 if (Op1C->getType()->getPrimitiveSizeInBits() <
2662 MulC->getType()->getPrimitiveSizeInBits())
2663 Op1C = ConstantExpr::getZExt(Op1C, MulC->getType());
2664 if (Op1C->getType()->getPrimitiveSizeInBits() >
2665 MulC->getType()->getPrimitiveSizeInBits())
2666 MulC = ConstantExpr::getZExt(MulC, Op1C->getType());
2668 // V == Base * (Mul0 * Op1), so return (Mul0 * Op1)
2669 Multiple = ConstantExpr::getMul(MulC, Op1C);
2673 if (ConstantInt *Mul0CI = dyn_cast<ConstantInt>(Mul0))
2674 if (Mul0CI->getValue() == 1) {
2675 // V == Base * Op1, so return Op1
2681 Value *Mul1 = nullptr;
2682 if (ComputeMultiple(Op1, Base, Mul1, LookThroughSExt, Depth+1)) {
2683 if (Constant *Op0C = dyn_cast<Constant>(Op0))
2684 if (Constant *MulC = dyn_cast<Constant>(Mul1)) {
2685 if (Op0C->getType()->getPrimitiveSizeInBits() <
2686 MulC->getType()->getPrimitiveSizeInBits())
2687 Op0C = ConstantExpr::getZExt(Op0C, MulC->getType());
2688 if (Op0C->getType()->getPrimitiveSizeInBits() >
2689 MulC->getType()->getPrimitiveSizeInBits())
2690 MulC = ConstantExpr::getZExt(MulC, Op0C->getType());
2692 // V == Base * (Mul1 * Op0), so return (Mul1 * Op0)
2693 Multiple = ConstantExpr::getMul(MulC, Op0C);
2697 if (ConstantInt *Mul1CI = dyn_cast<ConstantInt>(Mul1))
2698 if (Mul1CI->getValue() == 1) {
2699 // V == Base * Op0, so return Op0
2707 // We could not determine if V is a multiple of Base.
2711 Intrinsic::ID llvm::getIntrinsicForCallSite(ImmutableCallSite ICS,
2712 const TargetLibraryInfo *TLI) {
2713 const Function *F = ICS.getCalledFunction();
2715 return Intrinsic::not_intrinsic;
2717 if (F->isIntrinsic())
2718 return F->getIntrinsicID();
2721 return Intrinsic::not_intrinsic;
2724 // We're going to make assumptions on the semantics of the functions, check
2725 // that the target knows that it's available in this environment and it does
2726 // not have local linkage.
2727 if (!F || F->hasLocalLinkage() || !TLI->getLibFunc(*F, Func))
2728 return Intrinsic::not_intrinsic;
2730 if (!ICS.onlyReadsMemory())
2731 return Intrinsic::not_intrinsic;
2733 // Otherwise check if we have a call to a function that can be turned into a
2734 // vector intrinsic.
2741 return Intrinsic::sin;
2745 return Intrinsic::cos;
2749 return Intrinsic::exp;
2753 return Intrinsic::exp2;
2757 return Intrinsic::log;
2759 case LibFunc_log10f:
2760 case LibFunc_log10l:
2761 return Intrinsic::log10;
2765 return Intrinsic::log2;
2769 return Intrinsic::fabs;
2773 return Intrinsic::minnum;
2777 return Intrinsic::maxnum;
2778 case LibFunc_copysign:
2779 case LibFunc_copysignf:
2780 case LibFunc_copysignl:
2781 return Intrinsic::copysign;
2783 case LibFunc_floorf:
2784 case LibFunc_floorl:
2785 return Intrinsic::floor;
2789 return Intrinsic::ceil;
2791 case LibFunc_truncf:
2792 case LibFunc_truncl:
2793 return Intrinsic::trunc;
2797 return Intrinsic::rint;
2798 case LibFunc_nearbyint:
2799 case LibFunc_nearbyintf:
2800 case LibFunc_nearbyintl:
2801 return Intrinsic::nearbyint;
2803 case LibFunc_roundf:
2804 case LibFunc_roundl:
2805 return Intrinsic::round;
2809 return Intrinsic::pow;
2813 return Intrinsic::sqrt;
2816 return Intrinsic::not_intrinsic;
2819 /// Return true if we can prove that the specified FP value is never equal to
2822 /// NOTE: this function will need to be revisited when we support non-default
2824 bool llvm::CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
2826 if (auto *CFP = dyn_cast<ConstantFP>(V))
2827 return !CFP->getValueAPF().isNegZero();
2829 // Limit search depth.
2830 if (Depth == MaxDepth)
2833 auto *Op = dyn_cast<Operator>(V);
2837 // Check if the nsz fast-math flag is set.
2838 if (auto *FPO = dyn_cast<FPMathOperator>(Op))
2839 if (FPO->hasNoSignedZeros())
2842 // (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
2843 if (match(Op, m_FAdd(m_Value(), m_PosZeroFP())))
2846 // sitofp and uitofp turn into +0.0 for zero.
2847 if (isa<SIToFPInst>(Op) || isa<UIToFPInst>(Op))
2850 if (auto *Call = dyn_cast<CallInst>(Op)) {
2851 Intrinsic::ID IID = getIntrinsicForCallSite(Call, TLI);
2855 // sqrt(-0.0) = -0.0, no other negative results are possible.
2856 case Intrinsic::sqrt:
2857 case Intrinsic::canonicalize:
2858 return CannotBeNegativeZero(Call->getArgOperand(0), TLI, Depth + 1);
2860 case Intrinsic::fabs:
2868 /// If \p SignBitOnly is true, test for a known 0 sign bit rather than a
2869 /// standard ordered compare. e.g. make -0.0 olt 0.0 be true because of the sign
2870 /// bit despite comparing equal.
2871 static bool cannotBeOrderedLessThanZeroImpl(const Value *V,
2872 const TargetLibraryInfo *TLI,
2875 // TODO: This function does not do the right thing when SignBitOnly is true
2876 // and we're lowering to a hypothetical IEEE 754-compliant-but-evil platform
2877 // which flips the sign bits of NaNs. See
2878 // https://llvm.org/bugs/show_bug.cgi?id=31702.
2880 if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
2881 return !CFP->getValueAPF().isNegative() ||
2882 (!SignBitOnly && CFP->getValueAPF().isZero());
2885 // Handle vector of constants.
2886 if (auto *CV = dyn_cast<Constant>(V)) {
2887 if (CV->getType()->isVectorTy()) {
2888 unsigned NumElts = CV->getType()->getVectorNumElements();
2889 for (unsigned i = 0; i != NumElts; ++i) {
2890 auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(i));
2893 if (CFP->getValueAPF().isNegative() &&
2894 (SignBitOnly || !CFP->getValueAPF().isZero()))
2898 // All non-negative ConstantFPs.
2903 if (Depth == MaxDepth)
2904 return false; // Limit search depth.
2906 const Operator *I = dyn_cast<Operator>(V);
2910 switch (I->getOpcode()) {
2913 // Unsigned integers are always nonnegative.
2914 case Instruction::UIToFP:
2916 case Instruction::FMul:
2917 // x*x is always non-negative or a NaN.
2918 if (I->getOperand(0) == I->getOperand(1) &&
2919 (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()))
2923 case Instruction::FAdd:
2924 case Instruction::FDiv:
2925 case Instruction::FRem:
2926 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
2928 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
2930 case Instruction::Select:
2931 return cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
2933 cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
2935 case Instruction::FPExt:
2936 case Instruction::FPTrunc:
2937 // Widening/narrowing never change sign.
2938 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
2940 case Instruction::ExtractElement:
2941 // Look through extract element. At the moment we keep this simple and skip
2942 // tracking the specific element. But at least we might find information
2943 // valid for all elements of the vector.
2944 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
2946 case Instruction::Call:
2947 const auto *CI = cast<CallInst>(I);
2948 Intrinsic::ID IID = getIntrinsicForCallSite(CI, TLI);
2952 case Intrinsic::maxnum:
2953 return (isKnownNeverNaN(I->getOperand(0), TLI) &&
2954 cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI,
2955 SignBitOnly, Depth + 1)) ||
2956 (isKnownNeverNaN(I->getOperand(1), TLI) &&
2957 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI,
2958 SignBitOnly, Depth + 1));
2960 case Intrinsic::maximum:
2961 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
2963 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
2965 case Intrinsic::minnum:
2966 case Intrinsic::minimum:
2967 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
2969 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
2971 case Intrinsic::exp:
2972 case Intrinsic::exp2:
2973 case Intrinsic::fabs:
2976 case Intrinsic::sqrt:
2977 // sqrt(x) is always >= -0 or NaN. Moreover, sqrt(x) == -0 iff x == -0.
2980 return CI->hasNoNaNs() && (CI->hasNoSignedZeros() ||
2981 CannotBeNegativeZero(CI->getOperand(0), TLI));
2983 case Intrinsic::powi:
2984 if (ConstantInt *Exponent = dyn_cast<ConstantInt>(I->getOperand(1))) {
2985 // powi(x,n) is non-negative if n is even.
2986 if (Exponent->getBitWidth() <= 64 && Exponent->getSExtValue() % 2u == 0)
2989 // TODO: This is not correct. Given that exp is an integer, here are the
2990 // ways that pow can return a negative value:
2992 // pow(x, exp) --> negative if exp is odd and x is negative.
2993 // pow(-0, exp) --> -inf if exp is negative odd.
2994 // pow(-0, exp) --> -0 if exp is positive odd.
2995 // pow(-inf, exp) --> -0 if exp is negative odd.
2996 // pow(-inf, exp) --> -inf if exp is positive odd.
2998 // Therefore, if !SignBitOnly, we can return true if x >= +0 or x is NaN,
2999 // but we must return false if x == -0. Unfortunately we do not currently
3000 // have a way of expressing this constraint. See details in
3001 // https://llvm.org/bugs/show_bug.cgi?id=31702.
3002 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3005 case Intrinsic::fma:
3006 case Intrinsic::fmuladd:
3007 // x*x+y is non-negative if y is non-negative.
3008 return I->getOperand(0) == I->getOperand(1) &&
3009 (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()) &&
3010 cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
3018 bool llvm::CannotBeOrderedLessThanZero(const Value *V,
3019 const TargetLibraryInfo *TLI) {
3020 return cannotBeOrderedLessThanZeroImpl(V, TLI, false, 0);
3023 bool llvm::SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI) {
3024 return cannotBeOrderedLessThanZeroImpl(V, TLI, true, 0);
3027 bool llvm::isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
3029 assert(V->getType()->isFPOrFPVectorTy() && "Querying for NaN on non-FP type");
3031 // If we're told that NaNs won't happen, assume they won't.
3032 if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
3033 if (FPMathOp->hasNoNaNs())
3036 // Handle scalar constants.
3037 if (auto *CFP = dyn_cast<ConstantFP>(V))
3038 return !CFP->isNaN();
3040 if (Depth == MaxDepth)
3043 if (auto *Inst = dyn_cast<Instruction>(V)) {
3044 switch (Inst->getOpcode()) {
3045 case Instruction::FAdd:
3046 case Instruction::FMul:
3047 case Instruction::FSub:
3048 case Instruction::FDiv:
3049 case Instruction::FRem: {
3050 // TODO: Need isKnownNeverInfinity
3053 case Instruction::Select: {
3054 return isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
3055 isKnownNeverNaN(Inst->getOperand(2), TLI, Depth + 1);
3057 case Instruction::SIToFP:
3058 case Instruction::UIToFP:
3060 case Instruction::FPTrunc:
3061 case Instruction::FPExt:
3062 return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1);
3068 if (const auto *II = dyn_cast<IntrinsicInst>(V)) {
3069 switch (II->getIntrinsicID()) {
3070 case Intrinsic::canonicalize:
3071 case Intrinsic::fabs:
3072 case Intrinsic::copysign:
3073 case Intrinsic::exp:
3074 case Intrinsic::exp2:
3075 case Intrinsic::floor:
3076 case Intrinsic::ceil:
3077 case Intrinsic::trunc:
3078 case Intrinsic::rint:
3079 case Intrinsic::nearbyint:
3080 case Intrinsic::round:
3081 return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1);
3082 case Intrinsic::sqrt:
3083 return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) &&
3084 CannotBeOrderedLessThanZero(II->getArgOperand(0), TLI);
3090 // Bail out for constant expressions, but try to handle vector constants.
3091 if (!V->getType()->isVectorTy() || !isa<Constant>(V))
3094 // For vectors, verify that each element is not NaN.
3095 unsigned NumElts = V->getType()->getVectorNumElements();
3096 for (unsigned i = 0; i != NumElts; ++i) {
3097 Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
3100 if (isa<UndefValue>(Elt))
3102 auto *CElt = dyn_cast<ConstantFP>(Elt);
3103 if (!CElt || CElt->isNaN())
3106 // All elements were confirmed not-NaN or undefined.
3110 Value *llvm::isBytewiseValue(Value *V) {
3112 // All byte-wide stores are splatable, even of arbitrary variables.
3113 if (V->getType()->isIntegerTy(8))
3116 LLVMContext &Ctx = V->getContext();
3118 // Undef don't care.
3119 auto *UndefInt8 = UndefValue::get(Type::getInt8Ty(Ctx));
3120 if (isa<UndefValue>(V))
3123 Constant *C = dyn_cast<Constant>(V);
3125 // Conceptually, we could handle things like:
3126 // %a = zext i8 %X to i16
3127 // %b = shl i16 %a, 8
3128 // %c = or i16 %a, %b
3129 // but until there is an example that actually needs this, it doesn't seem
3130 // worth worrying about.
3134 // Handle 'null' ConstantArrayZero etc.
3135 if (C->isNullValue())
3136 return Constant::getNullValue(Type::getInt8Ty(Ctx));
3138 // Constant floating-point values can be handled as integer values if the
3139 // corresponding integer value is "byteable". An important case is 0.0.
3140 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
3142 if (CFP->getType()->isHalfTy())
3143 Ty = Type::getInt16Ty(Ctx);
3144 else if (CFP->getType()->isFloatTy())
3145 Ty = Type::getInt32Ty(Ctx);
3146 else if (CFP->getType()->isDoubleTy())
3147 Ty = Type::getInt64Ty(Ctx);
3148 // Don't handle long double formats, which have strange constraints.
3149 return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty)) : nullptr;
3152 // We can handle constant integers that are multiple of 8 bits.
3153 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
3154 if (CI->getBitWidth() % 8 == 0) {
3155 assert(CI->getBitWidth() > 8 && "8 bits should be handled above!");
3156 if (!CI->getValue().isSplat(8))
3158 return ConstantInt::get(Ctx, CI->getValue().trunc(8));
3162 auto Merge = [&](Value *LHS, Value *RHS) -> Value * {
3167 if (LHS == UndefInt8)
3169 if (RHS == UndefInt8)
3174 if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(C)) {
3175 Value *Val = UndefInt8;
3176 for (unsigned I = 0, E = CA->getNumElements(); I != E; ++I)
3177 if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I)))))
3182 if (isa<ConstantVector>(C)) {
3183 Constant *Splat = cast<ConstantVector>(C)->getSplatValue();
3184 return Splat ? isBytewiseValue(Splat) : nullptr;
3187 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) {
3188 Value *Val = UndefInt8;
3189 for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
3190 if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I)))))
3195 // Don't try to handle the handful of other constants.
3199 // This is the recursive version of BuildSubAggregate. It takes a few different
3200 // arguments. Idxs is the index within the nested struct From that we are
3201 // looking at now (which is of type IndexedType). IdxSkip is the number of
3202 // indices from Idxs that should be left out when inserting into the resulting
3203 // struct. To is the result struct built so far, new insertvalue instructions
3205 static Value *BuildSubAggregate(Value *From, Value* To, Type *IndexedType,
3206 SmallVectorImpl<unsigned> &Idxs,
3208 Instruction *InsertBefore) {
3209 StructType *STy = dyn_cast<StructType>(IndexedType);
3211 // Save the original To argument so we can modify it
3213 // General case, the type indexed by Idxs is a struct
3214 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
3215 // Process each struct element recursively
3218 To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip,
3222 // Couldn't find any inserted value for this index? Cleanup
3223 while (PrevTo != OrigTo) {
3224 InsertValueInst* Del = cast<InsertValueInst>(PrevTo);
3225 PrevTo = Del->getAggregateOperand();
3226 Del->eraseFromParent();
3228 // Stop processing elements
3232 // If we successfully found a value for each of our subaggregates
3236 // Base case, the type indexed by SourceIdxs is not a struct, or not all of
3237 // the struct's elements had a value that was inserted directly. In the latter
3238 // case, perhaps we can't determine each of the subelements individually, but
3239 // we might be able to find the complete struct somewhere.
3241 // Find the value that is at that particular spot
3242 Value *V = FindInsertedValue(From, Idxs);
3247 // Insert the value in the new (sub) aggregate
3248 return InsertValueInst::Create(To, V, makeArrayRef(Idxs).slice(IdxSkip),
3249 "tmp", InsertBefore);
3252 // This helper takes a nested struct and extracts a part of it (which is again a
3253 // struct) into a new value. For example, given the struct:
3254 // { a, { b, { c, d }, e } }
3255 // and the indices "1, 1" this returns
3258 // It does this by inserting an insertvalue for each element in the resulting
3259 // struct, as opposed to just inserting a single struct. This will only work if
3260 // each of the elements of the substruct are known (ie, inserted into From by an
3261 // insertvalue instruction somewhere).
3263 // All inserted insertvalue instructions are inserted before InsertBefore
3264 static Value *BuildSubAggregate(Value *From, ArrayRef<unsigned> idx_range,
3265 Instruction *InsertBefore) {
3266 assert(InsertBefore && "Must have someplace to insert!");
3267 Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(),
3269 Value *To = UndefValue::get(IndexedType);
3270 SmallVector<unsigned, 10> Idxs(idx_range.begin(), idx_range.end());
3271 unsigned IdxSkip = Idxs.size();
3273 return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore);
3276 /// Given an aggregate and a sequence of indices, see if the scalar value
3277 /// indexed is already around as a register, for example if it was inserted
3278 /// directly into the aggregate.
3280 /// If InsertBefore is not null, this function will duplicate (modified)
3281 /// insertvalues when a part of a nested struct is extracted.
3282 Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range,
3283 Instruction *InsertBefore) {
3284 // Nothing to index? Just return V then (this is useful at the end of our
3286 if (idx_range.empty())
3288 // We have indices, so V should have an indexable type.
3289 assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) &&
3290 "Not looking at a struct or array?");
3291 assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) &&
3292 "Invalid indices for type?");
3294 if (Constant *C = dyn_cast<Constant>(V)) {
3295 C = C->getAggregateElement(idx_range[0]);
3296 if (!C) return nullptr;
3297 return FindInsertedValue(C, idx_range.slice(1), InsertBefore);
3300 if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
3301 // Loop the indices for the insertvalue instruction in parallel with the
3302 // requested indices
3303 const unsigned *req_idx = idx_range.begin();
3304 for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
3305 i != e; ++i, ++req_idx) {
3306 if (req_idx == idx_range.end()) {
3307 // We can't handle this without inserting insertvalues
3311 // The requested index identifies a part of a nested aggregate. Handle
3312 // this specially. For example,
3313 // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
3314 // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
3315 // %C = extractvalue {i32, { i32, i32 } } %B, 1
3316 // This can be changed into
3317 // %A = insertvalue {i32, i32 } undef, i32 10, 0
3318 // %C = insertvalue {i32, i32 } %A, i32 11, 1
3319 // which allows the unused 0,0 element from the nested struct to be
3321 return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx),
3325 // This insert value inserts something else than what we are looking for.
3326 // See if the (aggregate) value inserted into has the value we are
3327 // looking for, then.
3329 return FindInsertedValue(I->getAggregateOperand(), idx_range,
3332 // If we end up here, the indices of the insertvalue match with those
3333 // requested (though possibly only partially). Now we recursively look at
3334 // the inserted value, passing any remaining indices.
3335 return FindInsertedValue(I->getInsertedValueOperand(),
3336 makeArrayRef(req_idx, idx_range.end()),
3340 if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
3341 // If we're extracting a value from an aggregate that was extracted from
3342 // something else, we can extract from that something else directly instead.
3343 // However, we will need to chain I's indices with the requested indices.
3345 // Calculate the number of indices required
3346 unsigned size = I->getNumIndices() + idx_range.size();
3347 // Allocate some space to put the new indices in
3348 SmallVector<unsigned, 5> Idxs;
3350 // Add indices from the extract value instruction
3351 Idxs.append(I->idx_begin(), I->idx_end());
3353 // Add requested indices
3354 Idxs.append(idx_range.begin(), idx_range.end());
3356 assert(Idxs.size() == size
3357 && "Number of indices added not correct?");
3359 return FindInsertedValue(I->getAggregateOperand(), Idxs, InsertBefore);
3361 // Otherwise, we don't know (such as, extracting from a function return value
3362 // or load instruction)
3366 /// Analyze the specified pointer to see if it can be expressed as a base
3367 /// pointer plus a constant offset. Return the base and offset to the caller.
3368 Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
3369 const DataLayout &DL) {
3370 unsigned BitWidth = DL.getIndexTypeSizeInBits(Ptr->getType());
3371 APInt ByteOffset(BitWidth, 0);
3373 // We walk up the defs but use a visited set to handle unreachable code. In
3374 // that case, we stop after accumulating the cycle once (not that it
3376 SmallPtrSet<Value *, 16> Visited;
3377 while (Visited.insert(Ptr).second) {
3378 if (Ptr->getType()->isVectorTy())
3381 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
3382 // If one of the values we have visited is an addrspacecast, then
3383 // the pointer type of this GEP may be different from the type
3384 // of the Ptr parameter which was passed to this function. This
3385 // means when we construct GEPOffset, we need to use the size
3386 // of GEP's pointer type rather than the size of the original
3388 APInt GEPOffset(DL.getIndexTypeSizeInBits(Ptr->getType()), 0);
3389 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
3392 APInt OrigByteOffset(ByteOffset);
3393 ByteOffset += GEPOffset.sextOrTrunc(ByteOffset.getBitWidth());
3394 if (ByteOffset.getMinSignedBits() > 64) {
3395 // Stop traversal if the pointer offset wouldn't fit into int64_t
3396 // (this should be removed if Offset is updated to an APInt)
3397 ByteOffset = OrigByteOffset;
3401 Ptr = GEP->getPointerOperand();
3402 } else if (Operator::getOpcode(Ptr) == Instruction::BitCast ||
3403 Operator::getOpcode(Ptr) == Instruction::AddrSpaceCast) {
3404 Ptr = cast<Operator>(Ptr)->getOperand(0);
3405 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
3406 if (GA->isInterposable())
3408 Ptr = GA->getAliasee();
3413 Offset = ByteOffset.getSExtValue();
3417 bool llvm::isGEPBasedOnPointerToString(const GEPOperator *GEP,
3418 unsigned CharSize) {
3419 // Make sure the GEP has exactly three arguments.
3420 if (GEP->getNumOperands() != 3)
3423 // Make sure the index-ee is a pointer to array of \p CharSize integers.
3425 ArrayType *AT = dyn_cast<ArrayType>(GEP->getSourceElementType());
3426 if (!AT || !AT->getElementType()->isIntegerTy(CharSize))
3429 // Check to make sure that the first operand of the GEP is an integer and
3430 // has value 0 so that we are sure we're indexing into the initializer.
3431 const ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
3432 if (!FirstIdx || !FirstIdx->isZero())
3438 bool llvm::getConstantDataArrayInfo(const Value *V,
3439 ConstantDataArraySlice &Slice,
3440 unsigned ElementSize, uint64_t Offset) {
3443 // Look through bitcast instructions and geps.
3444 V = V->stripPointerCasts();
3446 // If the value is a GEP instruction or constant expression, treat it as an
3448 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
3449 // The GEP operator should be based on a pointer to string constant, and is
3450 // indexing into the string constant.
3451 if (!isGEPBasedOnPointerToString(GEP, ElementSize))
3454 // If the second index isn't a ConstantInt, then this is a variable index
3455 // into the array. If this occurs, we can't say anything meaningful about
3457 uint64_t StartIdx = 0;
3458 if (const ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
3459 StartIdx = CI->getZExtValue();
3462 return getConstantDataArrayInfo(GEP->getOperand(0), Slice, ElementSize,
3466 // The GEP instruction, constant or instruction, must reference a global
3467 // variable that is a constant and is initialized. The referenced constant
3468 // initializer is the array that we'll use for optimization.
3469 const GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
3470 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
3473 const ConstantDataArray *Array;
3475 if (GV->getInitializer()->isNullValue()) {
3476 Type *GVTy = GV->getValueType();
3477 if ( (ArrayTy = dyn_cast<ArrayType>(GVTy)) ) {
3478 // A zeroinitializer for the array; there is no ConstantDataArray.
3481 const DataLayout &DL = GV->getParent()->getDataLayout();
3482 uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy);
3483 uint64_t Length = SizeInBytes / (ElementSize / 8);
3484 if (Length <= Offset)
3487 Slice.Array = nullptr;
3489 Slice.Length = Length - Offset;
3493 // This must be a ConstantDataArray.
3494 Array = dyn_cast<ConstantDataArray>(GV->getInitializer());
3497 ArrayTy = Array->getType();
3499 if (!ArrayTy->getElementType()->isIntegerTy(ElementSize))
3502 uint64_t NumElts = ArrayTy->getArrayNumElements();
3503 if (Offset > NumElts)
3506 Slice.Array = Array;
3507 Slice.Offset = Offset;
3508 Slice.Length = NumElts - Offset;
3512 /// This function computes the length of a null-terminated C string pointed to
3513 /// by V. If successful, it returns true and returns the string in Str.
3514 /// If unsuccessful, it returns false.
3515 bool llvm::getConstantStringInfo(const Value *V, StringRef &Str,
3516 uint64_t Offset, bool TrimAtNul) {
3517 ConstantDataArraySlice Slice;
3518 if (!getConstantDataArrayInfo(V, Slice, 8, Offset))
3521 if (Slice.Array == nullptr) {
3526 if (Slice.Length == 1) {
3527 Str = StringRef("", 1);
3530 // We cannot instantiate a StringRef as we do not have an appropriate string
3535 // Start out with the entire array in the StringRef.
3536 Str = Slice.Array->getAsString();
3537 // Skip over 'offset' bytes.
3538 Str = Str.substr(Slice.Offset);
3541 // Trim off the \0 and anything after it. If the array is not nul
3542 // terminated, we just return the whole end of string. The client may know
3543 // some other way that the string is length-bound.
3544 Str = Str.substr(0, Str.find('\0'));
3549 // These next two are very similar to the above, but also look through PHI
3551 // TODO: See if we can integrate these two together.
3553 /// If we can compute the length of the string pointed to by
3554 /// the specified pointer, return 'len+1'. If we can't, return 0.
3555 static uint64_t GetStringLengthH(const Value *V,
3556 SmallPtrSetImpl<const PHINode*> &PHIs,
3557 unsigned CharSize) {
3558 // Look through noop bitcast instructions.
3559 V = V->stripPointerCasts();
3561 // If this is a PHI node, there are two cases: either we have already seen it
3563 if (const PHINode *PN = dyn_cast<PHINode>(V)) {
3564 if (!PHIs.insert(PN).second)
3565 return ~0ULL; // already in the set.
3567 // If it was new, see if all the input strings are the same length.
3568 uint64_t LenSoFar = ~0ULL;
3569 for (Value *IncValue : PN->incoming_values()) {
3570 uint64_t Len = GetStringLengthH(IncValue, PHIs, CharSize);
3571 if (Len == 0) return 0; // Unknown length -> unknown.
3573 if (Len == ~0ULL) continue;
3575 if (Len != LenSoFar && LenSoFar != ~0ULL)
3576 return 0; // Disagree -> unknown.
3580 // Success, all agree.
3584 // strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
3585 if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
3586 uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs, CharSize);
3587 if (Len1 == 0) return 0;
3588 uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs, CharSize);
3589 if (Len2 == 0) return 0;
3590 if (Len1 == ~0ULL) return Len2;
3591 if (Len2 == ~0ULL) return Len1;
3592 if (Len1 != Len2) return 0;
3596 // Otherwise, see if we can read the string.
3597 ConstantDataArraySlice Slice;
3598 if (!getConstantDataArrayInfo(V, Slice, CharSize))
3601 if (Slice.Array == nullptr)
3604 // Search for nul characters
3605 unsigned NullIndex = 0;
3606 for (unsigned E = Slice.Length; NullIndex < E; ++NullIndex) {
3607 if (Slice.Array->getElementAsInteger(Slice.Offset + NullIndex) == 0)
3611 return NullIndex + 1;
3614 /// If we can compute the length of the string pointed to by
3615 /// the specified pointer, return 'len+1'. If we can't, return 0.
3616 uint64_t llvm::GetStringLength(const Value *V, unsigned CharSize) {
3617 if (!V->getType()->isPointerTy())
3620 SmallPtrSet<const PHINode*, 32> PHIs;
3621 uint64_t Len = GetStringLengthH(V, PHIs, CharSize);
3622 // If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
3623 // an empty string as a length.
3624 return Len == ~0ULL ? 1 : Len;
3627 const Value *llvm::getArgumentAliasingToReturnedPointer(const CallBase *Call) {
3629 "getArgumentAliasingToReturnedPointer only works on nonnull calls");
3630 if (const Value *RV = Call->getReturnedArgOperand())
3632 // This can be used only as a aliasing property.
3633 if (isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(Call))
3634 return Call->getArgOperand(0);
3638 bool llvm::isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
3639 const CallBase *Call) {
3640 return Call->getIntrinsicID() == Intrinsic::launder_invariant_group ||
3641 Call->getIntrinsicID() == Intrinsic::strip_invariant_group;
3644 /// \p PN defines a loop-variant pointer to an object. Check if the
3645 /// previous iteration of the loop was referring to the same object as \p PN.
3646 static bool isSameUnderlyingObjectInLoop(const PHINode *PN,
3647 const LoopInfo *LI) {
3648 // Find the loop-defined value.
3649 Loop *L = LI->getLoopFor(PN->getParent());
3650 if (PN->getNumIncomingValues() != 2)
3653 // Find the value from previous iteration.
3654 auto *PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(0));
3655 if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
3656 PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(1));
3657 if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
3660 // If a new pointer is loaded in the loop, the pointer references a different
3661 // object in every iteration. E.g.:
3665 if (auto *Load = dyn_cast<LoadInst>(PrevValue))
3666 if (!L->isLoopInvariant(Load->getPointerOperand()))
3671 Value *llvm::GetUnderlyingObject(Value *V, const DataLayout &DL,
3672 unsigned MaxLookup) {
3673 if (!V->getType()->isPointerTy())
3675 for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
3676 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
3677 V = GEP->getPointerOperand();
3678 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
3679 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
3680 V = cast<Operator>(V)->getOperand(0);
3681 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
3682 if (GA->isInterposable())
3684 V = GA->getAliasee();
3685 } else if (isa<AllocaInst>(V)) {
3686 // An alloca can't be further simplified.
3689 if (auto *Call = dyn_cast<CallBase>(V)) {
3690 // CaptureTracking can know about special capturing properties of some
3691 // intrinsics like launder.invariant.group, that can't be expressed with
3692 // the attributes, but have properties like returning aliasing pointer.
3693 // Because some analysis may assume that nocaptured pointer is not
3694 // returned from some special intrinsic (because function would have to
3695 // be marked with returns attribute), it is crucial to use this function
3696 // because it should be in sync with CaptureTracking. Not using it may
3697 // cause weird miscompilations where 2 aliasing pointers are assumed to
3699 if (auto *RP = getArgumentAliasingToReturnedPointer(Call)) {
3705 // See if InstructionSimplify knows any relevant tricks.
3706 if (Instruction *I = dyn_cast<Instruction>(V))
3707 // TODO: Acquire a DominatorTree and AssumptionCache and use them.
3708 if (Value *Simplified = SimplifyInstruction(I, {DL, I})) {
3715 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
3720 void llvm::GetUnderlyingObjects(Value *V, SmallVectorImpl<Value *> &Objects,
3721 const DataLayout &DL, LoopInfo *LI,
3722 unsigned MaxLookup) {
3723 SmallPtrSet<Value *, 4> Visited;
3724 SmallVector<Value *, 4> Worklist;
3725 Worklist.push_back(V);
3727 Value *P = Worklist.pop_back_val();
3728 P = GetUnderlyingObject(P, DL, MaxLookup);
3730 if (!Visited.insert(P).second)
3733 if (SelectInst *SI = dyn_cast<SelectInst>(P)) {
3734 Worklist.push_back(SI->getTrueValue());
3735 Worklist.push_back(SI->getFalseValue());
3739 if (PHINode *PN = dyn_cast<PHINode>(P)) {
3740 // If this PHI changes the underlying object in every iteration of the
3741 // loop, don't look through it. Consider:
3744 // Prev = Curr; // Prev = PHI (Prev_0, Curr)
3748 // Prev is tracking Curr one iteration behind so they refer to different
3749 // underlying objects.
3750 if (!LI || !LI->isLoopHeader(PN->getParent()) ||
3751 isSameUnderlyingObjectInLoop(PN, LI))
3752 for (Value *IncValue : PN->incoming_values())
3753 Worklist.push_back(IncValue);
3757 Objects.push_back(P);
3758 } while (!Worklist.empty());
3761 /// This is the function that does the work of looking through basic
3762 /// ptrtoint+arithmetic+inttoptr sequences.
3763 static const Value *getUnderlyingObjectFromInt(const Value *V) {
3765 if (const Operator *U = dyn_cast<Operator>(V)) {
3766 // If we find a ptrtoint, we can transfer control back to the
3767 // regular getUnderlyingObjectFromInt.
3768 if (U->getOpcode() == Instruction::PtrToInt)
3769 return U->getOperand(0);
3770 // If we find an add of a constant, a multiplied value, or a phi, it's
3771 // likely that the other operand will lead us to the base
3772 // object. We don't have to worry about the case where the
3773 // object address is somehow being computed by the multiply,
3774 // because our callers only care when the result is an
3775 // identifiable object.
3776 if (U->getOpcode() != Instruction::Add ||
3777 (!isa<ConstantInt>(U->getOperand(1)) &&
3778 Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
3779 !isa<PHINode>(U->getOperand(1))))
3781 V = U->getOperand(0);
3785 assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
3789 /// This is a wrapper around GetUnderlyingObjects and adds support for basic
3790 /// ptrtoint+arithmetic+inttoptr sequences.
3791 /// It returns false if unidentified object is found in GetUnderlyingObjects.
3792 bool llvm::getUnderlyingObjectsForCodeGen(const Value *V,
3793 SmallVectorImpl<Value *> &Objects,
3794 const DataLayout &DL) {
3795 SmallPtrSet<const Value *, 16> Visited;
3796 SmallVector<const Value *, 4> Working(1, V);
3798 V = Working.pop_back_val();
3800 SmallVector<Value *, 4> Objs;
3801 GetUnderlyingObjects(const_cast<Value *>(V), Objs, DL);
3803 for (Value *V : Objs) {
3804 if (!Visited.insert(V).second)
3806 if (Operator::getOpcode(V) == Instruction::IntToPtr) {
3808 getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
3809 if (O->getType()->isPointerTy()) {
3810 Working.push_back(O);
3814 // If GetUnderlyingObjects fails to find an identifiable object,
3815 // getUnderlyingObjectsForCodeGen also fails for safety.
3816 if (!isIdentifiedObject(V)) {
3820 Objects.push_back(const_cast<Value *>(V));
3822 } while (!Working.empty());
3826 /// Return true if the only users of this pointer are lifetime markers.
3827 bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
3828 for (const User *U : V->users()) {
3829 const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
3830 if (!II) return false;
3832 if (!II->isLifetimeStartOrEnd())
3838 bool llvm::isSafeToSpeculativelyExecute(const Value *V,
3839 const Instruction *CtxI,
3840 const DominatorTree *DT) {
3841 const Operator *Inst = dyn_cast<Operator>(V);
3845 for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
3846 if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
3850 switch (Inst->getOpcode()) {
3853 case Instruction::UDiv:
3854 case Instruction::URem: {
3855 // x / y is undefined if y == 0.
3857 if (match(Inst->getOperand(1), m_APInt(V)))
3861 case Instruction::SDiv:
3862 case Instruction::SRem: {
3863 // x / y is undefined if y == 0 or x == INT_MIN and y == -1
3864 const APInt *Numerator, *Denominator;
3865 if (!match(Inst->getOperand(1), m_APInt(Denominator)))
3867 // We cannot hoist this division if the denominator is 0.
3868 if (*Denominator == 0)
3870 // It's safe to hoist if the denominator is not 0 or -1.
3871 if (*Denominator != -1)
3873 // At this point we know that the denominator is -1. It is safe to hoist as
3874 // long we know that the numerator is not INT_MIN.
3875 if (match(Inst->getOperand(0), m_APInt(Numerator)))
3876 return !Numerator->isMinSignedValue();
3877 // The numerator *might* be MinSignedValue.
3880 case Instruction::Load: {
3881 const LoadInst *LI = cast<LoadInst>(Inst);
3882 if (!LI->isUnordered() ||
3883 // Speculative load may create a race that did not exist in the source.
3884 LI->getFunction()->hasFnAttribute(Attribute::SanitizeThread) ||
3885 // Speculative load may load data from dirty regions.
3886 LI->getFunction()->hasFnAttribute(Attribute::SanitizeAddress) ||
3887 LI->getFunction()->hasFnAttribute(Attribute::SanitizeHWAddress))
3889 const DataLayout &DL = LI->getModule()->getDataLayout();
3890 return isDereferenceableAndAlignedPointer(LI->getPointerOperand(),
3891 LI->getAlignment(), DL, CtxI, DT);
3893 case Instruction::Call: {
3894 auto *CI = cast<const CallInst>(Inst);
3895 const Function *Callee = CI->getCalledFunction();
3897 // The called function could have undefined behavior or side-effects, even
3898 // if marked readnone nounwind.
3899 return Callee && Callee->isSpeculatable();
3901 case Instruction::VAArg:
3902 case Instruction::Alloca:
3903 case Instruction::Invoke:
3904 case Instruction::PHI:
3905 case Instruction::Store:
3906 case Instruction::Ret:
3907 case Instruction::Br:
3908 case Instruction::IndirectBr:
3909 case Instruction::Switch:
3910 case Instruction::Unreachable:
3911 case Instruction::Fence:
3912 case Instruction::AtomicRMW:
3913 case Instruction::AtomicCmpXchg:
3914 case Instruction::LandingPad:
3915 case Instruction::Resume:
3916 case Instruction::CatchSwitch:
3917 case Instruction::CatchPad:
3918 case Instruction::CatchRet:
3919 case Instruction::CleanupPad:
3920 case Instruction::CleanupRet:
3921 return false; // Misc instructions which have effects
3925 bool llvm::mayBeMemoryDependent(const Instruction &I) {
3926 return I.mayReadOrWriteMemory() || !isSafeToSpeculativelyExecute(&I);
3929 OverflowResult llvm::computeOverflowForUnsignedMul(
3930 const Value *LHS, const Value *RHS, const DataLayout &DL,
3931 AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
3932 bool UseInstrInfo) {
3933 // Multiplying n * m significant bits yields a result of n + m significant
3934 // bits. If the total number of significant bits does not exceed the
3935 // result bit width (minus 1), there is no overflow.
3936 // This means if we have enough leading zero bits in the operands
3937 // we can guarantee that the result does not overflow.
3938 // Ref: "Hacker's Delight" by Henry Warren
3939 unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
3940 KnownBits LHSKnown(BitWidth);
3941 KnownBits RHSKnown(BitWidth);
3942 computeKnownBits(LHS, LHSKnown, DL, /*Depth=*/0, AC, CxtI, DT, nullptr,
3944 computeKnownBits(RHS, RHSKnown, DL, /*Depth=*/0, AC, CxtI, DT, nullptr,
3946 // Note that underestimating the number of zero bits gives a more
3947 // conservative answer.
3948 unsigned ZeroBits = LHSKnown.countMinLeadingZeros() +
3949 RHSKnown.countMinLeadingZeros();
3950 // First handle the easy case: if we have enough zero bits there's
3951 // definitely no overflow.
3952 if (ZeroBits >= BitWidth)
3953 return OverflowResult::NeverOverflows;
3955 // Get the largest possible values for each operand.
3956 APInt LHSMax = ~LHSKnown.Zero;
3957 APInt RHSMax = ~RHSKnown.Zero;
3959 // We know the multiply operation doesn't overflow if the maximum values for
3960 // each operand will not overflow after we multiply them together.
3962 (void)LHSMax.umul_ov(RHSMax, MaxOverflow);
3964 return OverflowResult::NeverOverflows;
3966 // We know it always overflows if multiplying the smallest possible values for
3967 // the operands also results in overflow.
3969 (void)LHSKnown.One.umul_ov(RHSKnown.One, MinOverflow);
3971 return OverflowResult::AlwaysOverflows;
3973 return OverflowResult::MayOverflow;
3977 llvm::computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
3978 const DataLayout &DL, AssumptionCache *AC,
3979 const Instruction *CxtI,
3980 const DominatorTree *DT, bool UseInstrInfo) {
3981 // Multiplying n * m significant bits yields a result of n + m significant
3982 // bits. If the total number of significant bits does not exceed the
3983 // result bit width (minus 1), there is no overflow.
3984 // This means if we have enough leading sign bits in the operands
3985 // we can guarantee that the result does not overflow.
3986 // Ref: "Hacker's Delight" by Henry Warren
3987 unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
3989 // Note that underestimating the number of sign bits gives a more
3990 // conservative answer.
3991 unsigned SignBits = ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) +
3992 ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT);
3994 // First handle the easy case: if we have enough sign bits there's
3995 // definitely no overflow.
3996 if (SignBits > BitWidth + 1)
3997 return OverflowResult::NeverOverflows;
3999 // There are two ambiguous cases where there can be no overflow:
4000 // SignBits == BitWidth + 1 and
4001 // SignBits == BitWidth
4002 // The second case is difficult to check, therefore we only handle the
4004 if (SignBits == BitWidth + 1) {
4005 // It overflows only when both arguments are negative and the true
4006 // product is exactly the minimum negative number.
4007 // E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
4008 // For simplicity we just check if at least one side is not negative.
4009 KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
4010 nullptr, UseInstrInfo);
4011 KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
4012 nullptr, UseInstrInfo);
4013 if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
4014 return OverflowResult::NeverOverflows;
4016 return OverflowResult::MayOverflow;
4019 OverflowResult llvm::computeOverflowForUnsignedAdd(
4020 const Value *LHS, const Value *RHS, const DataLayout &DL,
4021 AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
4022 bool UseInstrInfo) {
4023 KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
4024 nullptr, UseInstrInfo);
4025 if (LHSKnown.isNonNegative() || LHSKnown.isNegative()) {
4026 KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
4027 nullptr, UseInstrInfo);
4029 if (LHSKnown.isNegative() && RHSKnown.isNegative()) {
4030 // The sign bit is set in both cases: this MUST overflow.
4031 return OverflowResult::AlwaysOverflows;
4034 if (LHSKnown.isNonNegative() && RHSKnown.isNonNegative()) {
4035 // The sign bit is clear in both cases: this CANNOT overflow.
4036 return OverflowResult::NeverOverflows;
4040 return OverflowResult::MayOverflow;
4043 /// Return true if we can prove that adding the two values of the
4044 /// knownbits will not overflow.
4045 /// Otherwise return false.
4046 static bool checkRippleForSignedAdd(const KnownBits &LHSKnown,
4047 const KnownBits &RHSKnown) {
4048 // Addition of two 2's complement numbers having opposite signs will never
4050 if ((LHSKnown.isNegative() && RHSKnown.isNonNegative()) ||
4051 (LHSKnown.isNonNegative() && RHSKnown.isNegative()))
4054 // If either of the values is known to be non-negative, adding them can only
4055 // overflow if the second is also non-negative, so we can assume that.
4056 // Two non-negative numbers will only overflow if there is a carry to the
4057 // sign bit, so we can check if even when the values are as big as possible
4058 // there is no overflow to the sign bit.
4059 if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative()) {
4060 APInt MaxLHS = ~LHSKnown.Zero;
4061 MaxLHS.clearSignBit();
4062 APInt MaxRHS = ~RHSKnown.Zero;
4063 MaxRHS.clearSignBit();
4064 APInt Result = std::move(MaxLHS) + std::move(MaxRHS);
4065 return Result.isSignBitClear();
4068 // If either of the values is known to be negative, adding them can only
4069 // overflow if the second is also negative, so we can assume that.
4070 // Two negative number will only overflow if there is no carry to the sign
4071 // bit, so we can check if even when the values are as small as possible
4072 // there is overflow to the sign bit.
4073 if (LHSKnown.isNegative() || RHSKnown.isNegative()) {
4074 APInt MinLHS = LHSKnown.One;
4075 MinLHS.clearSignBit();
4076 APInt MinRHS = RHSKnown.One;
4077 MinRHS.clearSignBit();
4078 APInt Result = std::move(MinLHS) + std::move(MinRHS);
4079 return Result.isSignBitSet();
4082 // If we reached here it means that we know nothing about the sign bits.
4083 // In this case we can't know if there will be an overflow, since by
4084 // changing the sign bits any two values can be made to overflow.
4088 static OverflowResult computeOverflowForSignedAdd(const Value *LHS,
4090 const AddOperator *Add,
4091 const DataLayout &DL,
4092 AssumptionCache *AC,
4093 const Instruction *CxtI,
4094 const DominatorTree *DT) {
4095 if (Add && Add->hasNoSignedWrap()) {
4096 return OverflowResult::NeverOverflows;
4099 // If LHS and RHS each have at least two sign bits, the addition will look
4105 // If the carry into the most significant position is 0, X and Y can't both
4106 // be 1 and therefore the carry out of the addition is also 0.
4108 // If the carry into the most significant position is 1, X and Y can't both
4109 // be 0 and therefore the carry out of the addition is also 1.
4111 // Since the carry into the most significant position is always equal to
4112 // the carry out of the addition, there is no signed overflow.
4113 if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
4114 ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
4115 return OverflowResult::NeverOverflows;
4117 KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT);
4118 KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT);
4120 if (checkRippleForSignedAdd(LHSKnown, RHSKnown))
4121 return OverflowResult::NeverOverflows;
4123 // The remaining code needs Add to be available. Early returns if not so.
4125 return OverflowResult::MayOverflow;
4127 // If the sign of Add is the same as at least one of the operands, this add
4128 // CANNOT overflow. This is particularly useful when the sum is
4129 // @llvm.assume'ed non-negative rather than proved so from analyzing its
4131 bool LHSOrRHSKnownNonNegative =
4132 (LHSKnown.isNonNegative() || RHSKnown.isNonNegative());
4133 bool LHSOrRHSKnownNegative =
4134 (LHSKnown.isNegative() || RHSKnown.isNegative());
4135 if (LHSOrRHSKnownNonNegative || LHSOrRHSKnownNegative) {
4136 KnownBits AddKnown = computeKnownBits(Add, DL, /*Depth=*/0, AC, CxtI, DT);
4137 if ((AddKnown.isNonNegative() && LHSOrRHSKnownNonNegative) ||
4138 (AddKnown.isNegative() && LHSOrRHSKnownNegative)) {
4139 return OverflowResult::NeverOverflows;
4143 return OverflowResult::MayOverflow;
4146 OverflowResult llvm::computeOverflowForUnsignedSub(const Value *LHS,
4148 const DataLayout &DL,
4149 AssumptionCache *AC,
4150 const Instruction *CxtI,
4151 const DominatorTree *DT) {
4152 KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT);
4153 if (LHSKnown.isNonNegative() || LHSKnown.isNegative()) {
4154 KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT);
4156 // If the LHS is negative and the RHS is non-negative, no unsigned wrap.
4157 if (LHSKnown.isNegative() && RHSKnown.isNonNegative())
4158 return OverflowResult::NeverOverflows;
4160 // If the LHS is non-negative and the RHS negative, we always wrap.
4161 if (LHSKnown.isNonNegative() && RHSKnown.isNegative())
4162 return OverflowResult::AlwaysOverflows;
4165 return OverflowResult::MayOverflow;
4168 OverflowResult llvm::computeOverflowForSignedSub(const Value *LHS,
4170 const DataLayout &DL,
4171 AssumptionCache *AC,
4172 const Instruction *CxtI,
4173 const DominatorTree *DT) {
4174 // If LHS and RHS each have at least two sign bits, the subtraction
4176 if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
4177 ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
4178 return OverflowResult::NeverOverflows;
4180 KnownBits LHSKnown = computeKnownBits(LHS, DL, 0, AC, CxtI, DT);
4182 KnownBits RHSKnown = computeKnownBits(RHS, DL, 0, AC, CxtI, DT);
4184 // Subtraction of two 2's complement numbers having identical signs will
4186 if ((LHSKnown.isNegative() && RHSKnown.isNegative()) ||
4187 (LHSKnown.isNonNegative() && RHSKnown.isNonNegative()))
4188 return OverflowResult::NeverOverflows;
4190 // TODO: implement logic similar to checkRippleForAdd
4191 return OverflowResult::MayOverflow;
4194 bool llvm::isOverflowIntrinsicNoWrap(const IntrinsicInst *II,
4195 const DominatorTree &DT) {
4197 auto IID = II->getIntrinsicID();
4198 assert((IID == Intrinsic::sadd_with_overflow ||
4199 IID == Intrinsic::uadd_with_overflow ||
4200 IID == Intrinsic::ssub_with_overflow ||
4201 IID == Intrinsic::usub_with_overflow ||
4202 IID == Intrinsic::smul_with_overflow ||
4203 IID == Intrinsic::umul_with_overflow) &&
4204 "Not an overflow intrinsic!");
4207 SmallVector<const BranchInst *, 2> GuardingBranches;
4208 SmallVector<const ExtractValueInst *, 2> Results;
4210 for (const User *U : II->users()) {
4211 if (const auto *EVI = dyn_cast<ExtractValueInst>(U)) {
4212 assert(EVI->getNumIndices() == 1 && "Obvious from CI's type");
4214 if (EVI->getIndices()[0] == 0)
4215 Results.push_back(EVI);
4217 assert(EVI->getIndices()[0] == 1 && "Obvious from CI's type");
4219 for (const auto *U : EVI->users())
4220 if (const auto *B = dyn_cast<BranchInst>(U)) {
4221 assert(B->isConditional() && "How else is it using an i1?");
4222 GuardingBranches.push_back(B);
4226 // We are using the aggregate directly in a way we don't want to analyze
4227 // here (storing it to a global, say).
4232 auto AllUsesGuardedByBranch = [&](const BranchInst *BI) {
4233 BasicBlockEdge NoWrapEdge(BI->getParent(), BI->getSuccessor(1));
4234 if (!NoWrapEdge.isSingleEdge())
4237 // Check if all users of the add are provably no-wrap.
4238 for (const auto *Result : Results) {
4239 // If the extractvalue itself is not executed on overflow, the we don't
4240 // need to check each use separately, since domination is transitive.
4241 if (DT.dominates(NoWrapEdge, Result->getParent()))
4244 for (auto &RU : Result->uses())
4245 if (!DT.dominates(NoWrapEdge, RU))
4252 return llvm::any_of(GuardingBranches, AllUsesGuardedByBranch);
4256 OverflowResult llvm::computeOverflowForSignedAdd(const AddOperator *Add,
4257 const DataLayout &DL,
4258 AssumptionCache *AC,
4259 const Instruction *CxtI,
4260 const DominatorTree *DT) {
4261 return ::computeOverflowForSignedAdd(Add->getOperand(0), Add->getOperand(1),
4262 Add, DL, AC, CxtI, DT);
4265 OverflowResult llvm::computeOverflowForSignedAdd(const Value *LHS,
4267 const DataLayout &DL,
4268 AssumptionCache *AC,
4269 const Instruction *CxtI,
4270 const DominatorTree *DT) {
4271 return ::computeOverflowForSignedAdd(LHS, RHS, nullptr, DL, AC, CxtI, DT);
4274 bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
4275 // A memory operation returns normally if it isn't volatile. A volatile
4276 // operation is allowed to trap.
4278 // An atomic operation isn't guaranteed to return in a reasonable amount of
4279 // time because it's possible for another thread to interfere with it for an
4280 // arbitrary length of time, but programs aren't allowed to rely on that.
4281 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
4282 return !LI->isVolatile();
4283 if (const StoreInst *SI = dyn_cast<StoreInst>(I))
4284 return !SI->isVolatile();
4285 if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(I))
4286 return !CXI->isVolatile();
4287 if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I))
4288 return !RMWI->isVolatile();
4289 if (const MemIntrinsic *MII = dyn_cast<MemIntrinsic>(I))
4290 return !MII->isVolatile();
4292 // If there is no successor, then execution can't transfer to it.
4293 if (const auto *CRI = dyn_cast<CleanupReturnInst>(I))
4294 return !CRI->unwindsToCaller();
4295 if (const auto *CatchSwitch = dyn_cast<CatchSwitchInst>(I))
4296 return !CatchSwitch->unwindsToCaller();
4297 if (isa<ResumeInst>(I))
4299 if (isa<ReturnInst>(I))
4301 if (isa<UnreachableInst>(I))
4304 // Calls can throw, or contain an infinite loop, or kill the process.
4305 if (auto CS = ImmutableCallSite(I)) {
4306 // Call sites that throw have implicit non-local control flow.
4307 if (!CS.doesNotThrow())
4310 // Non-throwing call sites can loop infinitely, call exit/pthread_exit
4311 // etc. and thus not return. However, LLVM already assumes that
4313 // - Thread exiting actions are modeled as writes to memory invisible to
4316 // - Loops that don't have side effects (side effects are volatile/atomic
4317 // stores and IO) always terminate (see http://llvm.org/PR965).
4318 // Furthermore IO itself is also modeled as writes to memory invisible to
4321 // We rely on those assumptions here, and use the memory effects of the call
4322 // target as a proxy for checking that it always returns.
4324 // FIXME: This isn't aggressive enough; a call which only writes to a global
4325 // is guaranteed to return.
4326 return CS.onlyReadsMemory() || CS.onlyAccessesArgMemory() ||
4327 match(I, m_Intrinsic<Intrinsic::assume>()) ||
4328 match(I, m_Intrinsic<Intrinsic::sideeffect>());
4331 // Other instructions return normally.
4335 bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {
4336 // TODO: This is slightly consdervative for invoke instruction since exiting
4337 // via an exception *is* normal control for them.
4338 for (auto I = BB->begin(), E = BB->end(); I != E; ++I)
4339 if (!isGuaranteedToTransferExecutionToSuccessor(&*I))
4344 bool llvm::isGuaranteedToExecuteForEveryIteration(const Instruction *I,
4346 // The loop header is guaranteed to be executed for every iteration.
4348 // FIXME: Relax this constraint to cover all basic blocks that are
4349 // guaranteed to be executed at every iteration.
4350 if (I->getParent() != L->getHeader()) return false;
4352 for (const Instruction &LI : *L->getHeader()) {
4353 if (&LI == I) return true;
4354 if (!isGuaranteedToTransferExecutionToSuccessor(&LI)) return false;
4356 llvm_unreachable("Instruction not contained in its own parent basic block.");
4359 bool llvm::propagatesFullPoison(const Instruction *I) {
4360 switch (I->getOpcode()) {
4361 case Instruction::Add:
4362 case Instruction::Sub:
4363 case Instruction::Xor:
4364 case Instruction::Trunc:
4365 case Instruction::BitCast:
4366 case Instruction::AddrSpaceCast:
4367 case Instruction::Mul:
4368 case Instruction::Shl:
4369 case Instruction::GetElementPtr:
4370 // These operations all propagate poison unconditionally. Note that poison
4371 // is not any particular value, so xor or subtraction of poison with
4372 // itself still yields poison, not zero.
4375 case Instruction::AShr:
4376 case Instruction::SExt:
4377 // For these operations, one bit of the input is replicated across
4378 // multiple output bits. A replicated poison bit is still poison.
4381 case Instruction::ICmp:
4382 // Comparing poison with any value yields poison. This is why, for
4383 // instance, x s< (x +nsw 1) can be folded to true.
4391 const Value *llvm::getGuaranteedNonFullPoisonOp(const Instruction *I) {
4392 switch (I->getOpcode()) {
4393 case Instruction::Store:
4394 return cast<StoreInst>(I)->getPointerOperand();
4396 case Instruction::Load:
4397 return cast<LoadInst>(I)->getPointerOperand();
4399 case Instruction::AtomicCmpXchg:
4400 return cast<AtomicCmpXchgInst>(I)->getPointerOperand();
4402 case Instruction::AtomicRMW:
4403 return cast<AtomicRMWInst>(I)->getPointerOperand();
4405 case Instruction::UDiv:
4406 case Instruction::SDiv:
4407 case Instruction::URem:
4408 case Instruction::SRem:
4409 return I->getOperand(1);
4416 bool llvm::programUndefinedIfFullPoison(const Instruction *PoisonI) {
4417 // We currently only look for uses of poison values within the same basic
4418 // block, as that makes it easier to guarantee that the uses will be
4419 // executed given that PoisonI is executed.
4421 // FIXME: Expand this to consider uses beyond the same basic block. To do
4422 // this, look out for the distinction between post-dominance and strong
4424 const BasicBlock *BB = PoisonI->getParent();
4426 // Set of instructions that we have proved will yield poison if PoisonI
4428 SmallSet<const Value *, 16> YieldsPoison;
4429 SmallSet<const BasicBlock *, 4> Visited;
4430 YieldsPoison.insert(PoisonI);
4431 Visited.insert(PoisonI->getParent());
4433 BasicBlock::const_iterator Begin = PoisonI->getIterator(), End = BB->end();
4436 while (Iter++ < MaxDepth) {
4437 for (auto &I : make_range(Begin, End)) {
4438 if (&I != PoisonI) {
4439 const Value *NotPoison = getGuaranteedNonFullPoisonOp(&I);
4440 if (NotPoison != nullptr && YieldsPoison.count(NotPoison))
4442 if (!isGuaranteedToTransferExecutionToSuccessor(&I))
4446 // Mark poison that propagates from I through uses of I.
4447 if (YieldsPoison.count(&I)) {
4448 for (const User *User : I.users()) {
4449 const Instruction *UserI = cast<Instruction>(User);
4450 if (propagatesFullPoison(UserI))
4451 YieldsPoison.insert(User);
4456 if (auto *NextBB = BB->getSingleSuccessor()) {
4457 if (Visited.insert(NextBB).second) {
4459 Begin = BB->getFirstNonPHI()->getIterator();
4470 static bool isKnownNonNaN(const Value *V, FastMathFlags FMF) {
4474 if (auto *C = dyn_cast<ConstantFP>(V))
4477 if (auto *C = dyn_cast<ConstantDataVector>(V)) {
4478 if (!C->getElementType()->isFloatingPointTy())
4480 for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
4481 if (C->getElementAsAPFloat(I).isNaN())
4490 static bool isKnownNonZero(const Value *V) {
4491 if (auto *C = dyn_cast<ConstantFP>(V))
4492 return !C->isZero();
4494 if (auto *C = dyn_cast<ConstantDataVector>(V)) {
4495 if (!C->getElementType()->isFloatingPointTy())
4497 for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
4498 if (C->getElementAsAPFloat(I).isZero())
4507 /// Match clamp pattern for float types without care about NaNs or signed zeros.
4508 /// Given non-min/max outer cmp/select from the clamp pattern this
4509 /// function recognizes if it can be substitued by a "canonical" min/max
4511 static SelectPatternResult matchFastFloatClamp(CmpInst::Predicate Pred,
4512 Value *CmpLHS, Value *CmpRHS,
4513 Value *TrueVal, Value *FalseVal,
4514 Value *&LHS, Value *&RHS) {
4516 // X < C1 ? C1 : Min(X, C2) --> Max(C1, Min(X, C2))
4517 // X > C1 ? C1 : Max(X, C2) --> Min(C1, Max(X, C2))
4518 // and return description of the outer Max/Min.
4520 // First, check if select has inverse order:
4521 if (CmpRHS == FalseVal) {
4522 std::swap(TrueVal, FalseVal);
4523 Pred = CmpInst::getInversePredicate(Pred);
4526 // Assume success now. If there's no match, callers should not use these anyway.
4531 if (CmpRHS != TrueVal || !match(CmpRHS, m_APFloat(FC1)) || !FC1->isFinite())
4532 return {SPF_UNKNOWN, SPNB_NA, false};
4536 case CmpInst::FCMP_OLT:
4537 case CmpInst::FCMP_OLE:
4538 case CmpInst::FCMP_ULT:
4539 case CmpInst::FCMP_ULE:
4541 m_CombineOr(m_OrdFMin(m_Specific(CmpLHS), m_APFloat(FC2)),
4542 m_UnordFMin(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
4543 FC1->compare(*FC2) == APFloat::cmpResult::cmpLessThan)
4544 return {SPF_FMAXNUM, SPNB_RETURNS_ANY, false};
4546 case CmpInst::FCMP_OGT:
4547 case CmpInst::FCMP_OGE:
4548 case CmpInst::FCMP_UGT:
4549 case CmpInst::FCMP_UGE:
4551 m_CombineOr(m_OrdFMax(m_Specific(CmpLHS), m_APFloat(FC2)),
4552 m_UnordFMax(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
4553 FC1->compare(*FC2) == APFloat::cmpResult::cmpGreaterThan)
4554 return {SPF_FMINNUM, SPNB_RETURNS_ANY, false};
4560 return {SPF_UNKNOWN, SPNB_NA, false};
4563 /// Recognize variations of:
4564 /// CLAMP(v,l,h) ==> ((v) < (l) ? (l) : ((v) > (h) ? (h) : (v)))
4565 static SelectPatternResult matchClamp(CmpInst::Predicate Pred,
4566 Value *CmpLHS, Value *CmpRHS,
4567 Value *TrueVal, Value *FalseVal) {
4568 // Swap the select operands and predicate to match the patterns below.
4569 if (CmpRHS != TrueVal) {
4570 Pred = ICmpInst::getSwappedPredicate(Pred);
4571 std::swap(TrueVal, FalseVal);
4574 if (CmpRHS == TrueVal && match(CmpRHS, m_APInt(C1))) {
4576 // (X <s C1) ? C1 : SMIN(X, C2) ==> SMAX(SMIN(X, C2), C1)
4577 if (match(FalseVal, m_SMin(m_Specific(CmpLHS), m_APInt(C2))) &&
4578 C1->slt(*C2) && Pred == CmpInst::ICMP_SLT)
4579 return {SPF_SMAX, SPNB_NA, false};
4581 // (X >s C1) ? C1 : SMAX(X, C2) ==> SMIN(SMAX(X, C2), C1)
4582 if (match(FalseVal, m_SMax(m_Specific(CmpLHS), m_APInt(C2))) &&
4583 C1->sgt(*C2) && Pred == CmpInst::ICMP_SGT)
4584 return {SPF_SMIN, SPNB_NA, false};
4586 // (X <u C1) ? C1 : UMIN(X, C2) ==> UMAX(UMIN(X, C2), C1)
4587 if (match(FalseVal, m_UMin(m_Specific(CmpLHS), m_APInt(C2))) &&
4588 C1->ult(*C2) && Pred == CmpInst::ICMP_ULT)
4589 return {SPF_UMAX, SPNB_NA, false};
4591 // (X >u C1) ? C1 : UMAX(X, C2) ==> UMIN(UMAX(X, C2), C1)
4592 if (match(FalseVal, m_UMax(m_Specific(CmpLHS), m_APInt(C2))) &&
4593 C1->ugt(*C2) && Pred == CmpInst::ICMP_UGT)
4594 return {SPF_UMIN, SPNB_NA, false};
4596 return {SPF_UNKNOWN, SPNB_NA, false};
4599 /// Recognize variations of:
4600 /// a < c ? min(a,b) : min(b,c) ==> min(min(a,b),min(b,c))
4601 static SelectPatternResult matchMinMaxOfMinMax(CmpInst::Predicate Pred,
4602 Value *CmpLHS, Value *CmpRHS,
4603 Value *TVal, Value *FVal,
4605 // TODO: Allow FP min/max with nnan/nsz.
4606 assert(CmpInst::isIntPredicate(Pred) && "Expected integer comparison");
4609 SelectPatternResult L = matchSelectPattern(TVal, A, B, nullptr, Depth + 1);
4610 if (!SelectPatternResult::isMinOrMax(L.Flavor))
4611 return {SPF_UNKNOWN, SPNB_NA, false};
4614 SelectPatternResult R = matchSelectPattern(FVal, C, D, nullptr, Depth + 1);
4615 if (L.Flavor != R.Flavor)
4616 return {SPF_UNKNOWN, SPNB_NA, false};
4618 // We have something like: x Pred y ? min(a, b) : min(c, d).
4619 // Try to match the compare to the min/max operations of the select operands.
4620 // First, make sure we have the right compare predicate.
4623 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) {
4624 Pred = ICmpInst::getSwappedPredicate(Pred);
4625 std::swap(CmpLHS, CmpRHS);
4627 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
4629 return {SPF_UNKNOWN, SPNB_NA, false};
4631 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) {
4632 Pred = ICmpInst::getSwappedPredicate(Pred);
4633 std::swap(CmpLHS, CmpRHS);
4635 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
4637 return {SPF_UNKNOWN, SPNB_NA, false};
4639 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
4640 Pred = ICmpInst::getSwappedPredicate(Pred);
4641 std::swap(CmpLHS, CmpRHS);
4643 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE)
4645 return {SPF_UNKNOWN, SPNB_NA, false};
4647 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
4648 Pred = ICmpInst::getSwappedPredicate(Pred);
4649 std::swap(CmpLHS, CmpRHS);
4651 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
4653 return {SPF_UNKNOWN, SPNB_NA, false};
4655 return {SPF_UNKNOWN, SPNB_NA, false};
4658 // If there is a common operand in the already matched min/max and the other
4659 // min/max operands match the compare operands (either directly or inverted),
4660 // then this is min/max of the same flavor.
4662 // a pred c ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
4663 // ~c pred ~a ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
4665 if ((CmpLHS == A && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
4666 match(A, m_Not(m_Specific(CmpRHS)))))
4667 return {L.Flavor, SPNB_NA, false};
4669 // a pred d ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
4670 // ~d pred ~a ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
4672 if ((CmpLHS == A && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
4673 match(A, m_Not(m_Specific(CmpRHS)))))
4674 return {L.Flavor, SPNB_NA, false};
4676 // b pred c ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
4677 // ~c pred ~b ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
4679 if ((CmpLHS == B && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
4680 match(B, m_Not(m_Specific(CmpRHS)))))
4681 return {L.Flavor, SPNB_NA, false};
4683 // b pred d ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
4684 // ~d pred ~b ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
4686 if ((CmpLHS == B && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
4687 match(B, m_Not(m_Specific(CmpRHS)))))
4688 return {L.Flavor, SPNB_NA, false};
4691 return {SPF_UNKNOWN, SPNB_NA, false};
4694 /// Match non-obvious integer minimum and maximum sequences.
4695 static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
4696 Value *CmpLHS, Value *CmpRHS,
4697 Value *TrueVal, Value *FalseVal,
4698 Value *&LHS, Value *&RHS,
4700 // Assume success. If there's no match, callers should not use these anyway.
4704 SelectPatternResult SPR = matchClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal);
4705 if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
4708 SPR = matchMinMaxOfMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, Depth);
4709 if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
4712 if (Pred != CmpInst::ICMP_SGT && Pred != CmpInst::ICMP_SLT)
4713 return {SPF_UNKNOWN, SPNB_NA, false};
4716 // (X >s Y) ? 0 : Z ==> (Z >s 0) ? 0 : Z ==> SMIN(Z, 0)
4717 // (X <s Y) ? 0 : Z ==> (Z <s 0) ? 0 : Z ==> SMAX(Z, 0)
4718 if (match(TrueVal, m_Zero()) &&
4719 match(FalseVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
4720 return {Pred == CmpInst::ICMP_SGT ? SPF_SMIN : SPF_SMAX, SPNB_NA, false};
4723 // (X >s Y) ? Z : 0 ==> (Z >s 0) ? Z : 0 ==> SMAX(Z, 0)
4724 // (X <s Y) ? Z : 0 ==> (Z <s 0) ? Z : 0 ==> SMIN(Z, 0)
4725 if (match(FalseVal, m_Zero()) &&
4726 match(TrueVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
4727 return {Pred == CmpInst::ICMP_SGT ? SPF_SMAX : SPF_SMIN, SPNB_NA, false};
4730 if (!match(CmpRHS, m_APInt(C1)))
4731 return {SPF_UNKNOWN, SPNB_NA, false};
4733 // An unsigned min/max can be written with a signed compare.
4735 if ((CmpLHS == TrueVal && match(FalseVal, m_APInt(C2))) ||
4736 (CmpLHS == FalseVal && match(TrueVal, m_APInt(C2)))) {
4737 // Is the sign bit set?
4738 // (X <s 0) ? X : MAXVAL ==> (X >u MAXVAL) ? X : MAXVAL ==> UMAX
4739 // (X <s 0) ? MAXVAL : X ==> (X >u MAXVAL) ? MAXVAL : X ==> UMIN
4740 if (Pred == CmpInst::ICMP_SLT && C1->isNullValue() &&
4741 C2->isMaxSignedValue())
4742 return {CmpLHS == TrueVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
4744 // Is the sign bit clear?
4745 // (X >s -1) ? MINVAL : X ==> (X <u MINVAL) ? MINVAL : X ==> UMAX
4746 // (X >s -1) ? X : MINVAL ==> (X <u MINVAL) ? X : MINVAL ==> UMIN
4747 if (Pred == CmpInst::ICMP_SGT && C1->isAllOnesValue() &&
4748 C2->isMinSignedValue())
4749 return {CmpLHS == FalseVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
4752 // Look through 'not' ops to find disguised signed min/max.
4753 // (X >s C) ? ~X : ~C ==> (~X <s ~C) ? ~X : ~C ==> SMIN(~X, ~C)
4754 // (X <s C) ? ~X : ~C ==> (~X >s ~C) ? ~X : ~C ==> SMAX(~X, ~C)
4755 if (match(TrueVal, m_Not(m_Specific(CmpLHS))) &&
4756 match(FalseVal, m_APInt(C2)) && ~(*C1) == *C2)
4757 return {Pred == CmpInst::ICMP_SGT ? SPF_SMIN : SPF_SMAX, SPNB_NA, false};
4759 // (X >s C) ? ~C : ~X ==> (~X <s ~C) ? ~C : ~X ==> SMAX(~C, ~X)
4760 // (X <s C) ? ~C : ~X ==> (~X >s ~C) ? ~C : ~X ==> SMIN(~C, ~X)
4761 if (match(FalseVal, m_Not(m_Specific(CmpLHS))) &&
4762 match(TrueVal, m_APInt(C2)) && ~(*C1) == *C2)
4763 return {Pred == CmpInst::ICMP_SGT ? SPF_SMAX : SPF_SMIN, SPNB_NA, false};
4765 return {SPF_UNKNOWN, SPNB_NA, false};
4768 bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
4769 assert(X && Y && "Invalid operand");
4771 // X = sub (0, Y) || X = sub nsw (0, Y)
4772 if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
4773 (NeedNSW && match(X, m_NSWSub(m_ZeroInt(), m_Specific(Y)))))
4776 // Y = sub (0, X) || Y = sub nsw (0, X)
4777 if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
4778 (NeedNSW && match(Y, m_NSWSub(m_ZeroInt(), m_Specific(X)))))
4781 // X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
4783 return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
4784 match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
4785 (NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
4786 match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
4789 static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
4791 Value *CmpLHS, Value *CmpRHS,
4792 Value *TrueVal, Value *FalseVal,
4793 Value *&LHS, Value *&RHS,
4795 if (CmpInst::isFPPredicate(Pred)) {
4796 // IEEE-754 ignores the sign of 0.0 in comparisons. So if the select has one
4797 // 0.0 operand, set the compare's 0.0 operands to that same value for the
4798 // purpose of identifying min/max. Disregard vector constants with undefined
4799 // elements because those can not be back-propagated for analysis.
4800 Value *OutputZeroVal = nullptr;
4801 if (match(TrueVal, m_AnyZeroFP()) && !match(FalseVal, m_AnyZeroFP()) &&
4802 !cast<Constant>(TrueVal)->containsUndefElement())
4803 OutputZeroVal = TrueVal;
4804 else if (match(FalseVal, m_AnyZeroFP()) && !match(TrueVal, m_AnyZeroFP()) &&
4805 !cast<Constant>(FalseVal)->containsUndefElement())
4806 OutputZeroVal = FalseVal;
4808 if (OutputZeroVal) {
4809 if (match(CmpLHS, m_AnyZeroFP()))
4810 CmpLHS = OutputZeroVal;
4811 if (match(CmpRHS, m_AnyZeroFP()))
4812 CmpRHS = OutputZeroVal;
4819 // Signed zero may return inconsistent results between implementations.
4820 // (0.0 <= -0.0) ? 0.0 : -0.0 // Returns 0.0
4821 // minNum(0.0, -0.0) // May return -0.0 or 0.0 (IEEE 754-2008 5.3.1)
4822 // Therefore, we behave conservatively and only proceed if at least one of the
4823 // operands is known to not be zero or if we don't care about signed zero.
4826 // FIXME: Include OGT/OLT/UGT/ULT.
4827 case CmpInst::FCMP_OGE: case CmpInst::FCMP_OLE:
4828 case CmpInst::FCMP_UGE: case CmpInst::FCMP_ULE:
4829 if (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
4830 !isKnownNonZero(CmpRHS))
4831 return {SPF_UNKNOWN, SPNB_NA, false};
4834 SelectPatternNaNBehavior NaNBehavior = SPNB_NA;
4835 bool Ordered = false;
4837 // When given one NaN and one non-NaN input:
4838 // - maxnum/minnum (C99 fmaxf()/fminf()) return the non-NaN input.
4839 // - A simple C99 (a < b ? a : b) construction will return 'b' (as the
4840 // ordered comparison fails), which could be NaN or non-NaN.
4841 // so here we discover exactly what NaN behavior is required/accepted.
4842 if (CmpInst::isFPPredicate(Pred)) {
4843 bool LHSSafe = isKnownNonNaN(CmpLHS, FMF);
4844 bool RHSSafe = isKnownNonNaN(CmpRHS, FMF);
4846 if (LHSSafe && RHSSafe) {
4847 // Both operands are known non-NaN.
4848 NaNBehavior = SPNB_RETURNS_ANY;
4849 } else if (CmpInst::isOrdered(Pred)) {
4850 // An ordered comparison will return false when given a NaN, so it
4854 // LHS is non-NaN, so if RHS is NaN then NaN will be returned.
4855 NaNBehavior = SPNB_RETURNS_NAN;
4857 NaNBehavior = SPNB_RETURNS_OTHER;
4859 // Completely unsafe.
4860 return {SPF_UNKNOWN, SPNB_NA, false};
4863 // An unordered comparison will return true when given a NaN, so it
4866 // LHS is non-NaN, so if RHS is NaN then non-NaN will be returned.
4867 NaNBehavior = SPNB_RETURNS_OTHER;
4869 NaNBehavior = SPNB_RETURNS_NAN;
4871 // Completely unsafe.
4872 return {SPF_UNKNOWN, SPNB_NA, false};
4876 if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
4877 std::swap(CmpLHS, CmpRHS);
4878 Pred = CmpInst::getSwappedPredicate(Pred);
4879 if (NaNBehavior == SPNB_RETURNS_NAN)
4880 NaNBehavior = SPNB_RETURNS_OTHER;
4881 else if (NaNBehavior == SPNB_RETURNS_OTHER)
4882 NaNBehavior = SPNB_RETURNS_NAN;
4886 // ([if]cmp X, Y) ? X : Y
4887 if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
4889 default: return {SPF_UNKNOWN, SPNB_NA, false}; // Equality.
4890 case ICmpInst::ICMP_UGT:
4891 case ICmpInst::ICMP_UGE: return {SPF_UMAX, SPNB_NA, false};
4892 case ICmpInst::ICMP_SGT:
4893 case ICmpInst::ICMP_SGE: return {SPF_SMAX, SPNB_NA, false};
4894 case ICmpInst::ICMP_ULT:
4895 case ICmpInst::ICMP_ULE: return {SPF_UMIN, SPNB_NA, false};
4896 case ICmpInst::ICMP_SLT:
4897 case ICmpInst::ICMP_SLE: return {SPF_SMIN, SPNB_NA, false};
4898 case FCmpInst::FCMP_UGT:
4899 case FCmpInst::FCMP_UGE:
4900 case FCmpInst::FCMP_OGT:
4901 case FCmpInst::FCMP_OGE: return {SPF_FMAXNUM, NaNBehavior, Ordered};
4902 case FCmpInst::FCMP_ULT:
4903 case FCmpInst::FCMP_ULE:
4904 case FCmpInst::FCMP_OLT:
4905 case FCmpInst::FCMP_OLE: return {SPF_FMINNUM, NaNBehavior, Ordered};
4909 if (isKnownNegation(TrueVal, FalseVal)) {
4910 // Sign-extending LHS does not change its sign, so TrueVal/FalseVal can
4911 // match against either LHS or sext(LHS).
4912 auto MaybeSExtCmpLHS =
4913 m_CombineOr(m_Specific(CmpLHS), m_SExt(m_Specific(CmpLHS)));
4914 auto ZeroOrAllOnes = m_CombineOr(m_ZeroInt(), m_AllOnes());
4915 auto ZeroOrOne = m_CombineOr(m_ZeroInt(), m_One());
4916 if (match(TrueVal, MaybeSExtCmpLHS)) {
4917 // Set the return values. If the compare uses the negated value (-X >s 0),
4918 // swap the return values because the negated value is always 'RHS'.
4921 if (match(CmpLHS, m_Neg(m_Specific(FalseVal))))
4922 std::swap(LHS, RHS);
4924 // (X >s 0) ? X : -X or (X >s -1) ? X : -X --> ABS(X)
4925 // (-X >s 0) ? -X : X or (-X >s -1) ? -X : X --> ABS(X)
4926 if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
4927 return {SPF_ABS, SPNB_NA, false};
4929 // (X <s 0) ? X : -X or (X <s 1) ? X : -X --> NABS(X)
4930 // (-X <s 0) ? -X : X or (-X <s 1) ? -X : X --> NABS(X)
4931 if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
4932 return {SPF_NABS, SPNB_NA, false};
4934 else if (match(FalseVal, MaybeSExtCmpLHS)) {
4935 // Set the return values. If the compare uses the negated value (-X >s 0),
4936 // swap the return values because the negated value is always 'RHS'.
4939 if (match(CmpLHS, m_Neg(m_Specific(TrueVal))))
4940 std::swap(LHS, RHS);
4942 // (X >s 0) ? -X : X or (X >s -1) ? -X : X --> NABS(X)
4943 // (-X >s 0) ? X : -X or (-X >s -1) ? X : -X --> NABS(X)
4944 if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
4945 return {SPF_NABS, SPNB_NA, false};
4947 // (X <s 0) ? -X : X or (X <s 1) ? -X : X --> ABS(X)
4948 // (-X <s 0) ? X : -X or (-X <s 1) ? X : -X --> ABS(X)
4949 if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
4950 return {SPF_ABS, SPNB_NA, false};
4954 if (CmpInst::isIntPredicate(Pred))
4955 return matchMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS, Depth);
4957 // According to (IEEE 754-2008 5.3.1), minNum(0.0, -0.0) and similar
4958 // may return either -0.0 or 0.0, so fcmp/select pair has stricter
4959 // semantics than minNum. Be conservative in such case.
4960 if (NaNBehavior != SPNB_RETURNS_ANY ||
4961 (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
4962 !isKnownNonZero(CmpRHS)))
4963 return {SPF_UNKNOWN, SPNB_NA, false};
4965 return matchFastFloatClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS);
4968 /// Helps to match a select pattern in case of a type mismatch.
4970 /// The function processes the case when type of true and false values of a
4971 /// select instruction differs from type of the cmp instruction operands because
4972 /// of a cast instruction. The function checks if it is legal to move the cast
4973 /// operation after "select". If yes, it returns the new second value of
4974 /// "select" (with the assumption that cast is moved):
4975 /// 1. As operand of cast instruction when both values of "select" are same cast
4977 /// 2. As restored constant (by applying reverse cast operation) when the first
4978 /// value of the "select" is a cast operation and the second value is a
4980 /// NOTE: We return only the new second value because the first value could be
4981 /// accessed as operand of cast instruction.
4982 static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
4983 Instruction::CastOps *CastOp) {
4984 auto *Cast1 = dyn_cast<CastInst>(V1);
4988 *CastOp = Cast1->getOpcode();
4989 Type *SrcTy = Cast1->getSrcTy();
4990 if (auto *Cast2 = dyn_cast<CastInst>(V2)) {
4991 // If V1 and V2 are both the same cast from the same type, look through V1.
4992 if (*CastOp == Cast2->getOpcode() && SrcTy == Cast2->getSrcTy())
4993 return Cast2->getOperand(0);
4997 auto *C = dyn_cast<Constant>(V2);
5001 Constant *CastedTo = nullptr;
5003 case Instruction::ZExt:
5004 if (CmpI->isUnsigned())
5005 CastedTo = ConstantExpr::getTrunc(C, SrcTy);
5007 case Instruction::SExt:
5008 if (CmpI->isSigned())
5009 CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
5011 case Instruction::Trunc:
5013 if (match(CmpI->getOperand(1), m_Constant(CmpConst)) &&
5014 CmpConst->getType() == SrcTy) {
5015 // Here we have the following case:
5017 // %cond = cmp iN %x, CmpConst
5018 // %tr = trunc iN %x to iK
5019 // %narrowsel = select i1 %cond, iK %t, iK C
5021 // We can always move trunc after select operation:
5023 // %cond = cmp iN %x, CmpConst
5024 // %widesel = select i1 %cond, iN %x, iN CmpConst
5025 // %tr = trunc iN %widesel to iK
5027 // Note that C could be extended in any way because we don't care about
5028 // upper bits after truncation. It can't be abs pattern, because it would
5031 // select i1 %cond, x, -x.
5033 // So only min/max pattern could be matched. Such match requires widened C
5034 // == CmpConst. That is why set widened C = CmpConst, condition trunc
5035 // CmpConst == C is checked below.
5036 CastedTo = CmpConst;
5038 CastedTo = ConstantExpr::getIntegerCast(C, SrcTy, CmpI->isSigned());
5041 case Instruction::FPTrunc:
5042 CastedTo = ConstantExpr::getFPExtend(C, SrcTy, true);
5044 case Instruction::FPExt:
5045 CastedTo = ConstantExpr::getFPTrunc(C, SrcTy, true);
5047 case Instruction::FPToUI:
5048 CastedTo = ConstantExpr::getUIToFP(C, SrcTy, true);
5050 case Instruction::FPToSI:
5051 CastedTo = ConstantExpr::getSIToFP(C, SrcTy, true);
5053 case Instruction::UIToFP:
5054 CastedTo = ConstantExpr::getFPToUI(C, SrcTy, true);
5056 case Instruction::SIToFP:
5057 CastedTo = ConstantExpr::getFPToSI(C, SrcTy, true);
5066 // Make sure the cast doesn't lose any information.
5067 Constant *CastedBack =
5068 ConstantExpr::getCast(*CastOp, CastedTo, C->getType(), true);
5069 if (CastedBack != C)
5075 SelectPatternResult llvm::matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
5076 Instruction::CastOps *CastOp,
5078 if (Depth >= MaxDepth)
5079 return {SPF_UNKNOWN, SPNB_NA, false};
5081 SelectInst *SI = dyn_cast<SelectInst>(V);
5082 if (!SI) return {SPF_UNKNOWN, SPNB_NA, false};
5084 CmpInst *CmpI = dyn_cast<CmpInst>(SI->getCondition());
5085 if (!CmpI) return {SPF_UNKNOWN, SPNB_NA, false};
5087 CmpInst::Predicate Pred = CmpI->getPredicate();
5088 Value *CmpLHS = CmpI->getOperand(0);
5089 Value *CmpRHS = CmpI->getOperand(1);
5090 Value *TrueVal = SI->getTrueValue();
5091 Value *FalseVal = SI->getFalseValue();
5093 if (isa<FPMathOperator>(CmpI))
5094 FMF = CmpI->getFastMathFlags();
5097 if (CmpI->isEquality())
5098 return {SPF_UNKNOWN, SPNB_NA, false};
5100 // Deal with type mismatches.
5101 if (CastOp && CmpLHS->getType() != TrueVal->getType()) {
5102 if (Value *C = lookThroughCast(CmpI, TrueVal, FalseVal, CastOp)) {
5103 // If this is a potential fmin/fmax with a cast to integer, then ignore
5104 // -0.0 because there is no corresponding integer value.
5105 if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
5106 FMF.setNoSignedZeros();
5107 return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
5108 cast<CastInst>(TrueVal)->getOperand(0), C,
5111 if (Value *C = lookThroughCast(CmpI, FalseVal, TrueVal, CastOp)) {
5112 // If this is a potential fmin/fmax with a cast to integer, then ignore
5113 // -0.0 because there is no corresponding integer value.
5114 if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
5115 FMF.setNoSignedZeros();
5116 return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
5117 C, cast<CastInst>(FalseVal)->getOperand(0),
5121 return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS, TrueVal, FalseVal,
5125 CmpInst::Predicate llvm::getMinMaxPred(SelectPatternFlavor SPF, bool Ordered) {
5126 if (SPF == SPF_SMIN) return ICmpInst::ICMP_SLT;
5127 if (SPF == SPF_UMIN) return ICmpInst::ICMP_ULT;
5128 if (SPF == SPF_SMAX) return ICmpInst::ICMP_SGT;
5129 if (SPF == SPF_UMAX) return ICmpInst::ICMP_UGT;
5130 if (SPF == SPF_FMINNUM)
5131 return Ordered ? FCmpInst::FCMP_OLT : FCmpInst::FCMP_ULT;
5132 if (SPF == SPF_FMAXNUM)
5133 return Ordered ? FCmpInst::FCMP_OGT : FCmpInst::FCMP_UGT;
5134 llvm_unreachable("unhandled!");
5137 SelectPatternFlavor llvm::getInverseMinMaxFlavor(SelectPatternFlavor SPF) {
5138 if (SPF == SPF_SMIN) return SPF_SMAX;
5139 if (SPF == SPF_UMIN) return SPF_UMAX;
5140 if (SPF == SPF_SMAX) return SPF_SMIN;
5141 if (SPF == SPF_UMAX) return SPF_UMIN;
5142 llvm_unreachable("unhandled!");
5145 CmpInst::Predicate llvm::getInverseMinMaxPred(SelectPatternFlavor SPF) {
5146 return getMinMaxPred(getInverseMinMaxFlavor(SPF));
5149 /// Return true if "icmp Pred LHS RHS" is always true.
5150 static bool isTruePredicate(CmpInst::Predicate Pred, const Value *LHS,
5151 const Value *RHS, const DataLayout &DL,
5153 assert(!LHS->getType()->isVectorTy() && "TODO: extend to handle vectors!");
5154 if (ICmpInst::isTrueWhenEqual(Pred) && LHS == RHS)
5161 case CmpInst::ICMP_SLE: {
5164 // LHS s<= LHS +_{nsw} C if C >= 0
5165 if (match(RHS, m_NSWAdd(m_Specific(LHS), m_APInt(C))))
5166 return !C->isNegative();
5170 case CmpInst::ICMP_ULE: {
5173 // LHS u<= LHS +_{nuw} C for any C
5174 if (match(RHS, m_NUWAdd(m_Specific(LHS), m_APInt(C))))
5177 // Match A to (X +_{nuw} CA) and B to (X +_{nuw} CB)
5178 auto MatchNUWAddsToSameValue = [&](const Value *A, const Value *B,
5180 const APInt *&CA, const APInt *&CB) {
5181 if (match(A, m_NUWAdd(m_Value(X), m_APInt(CA))) &&
5182 match(B, m_NUWAdd(m_Specific(X), m_APInt(CB))))
5185 // If X & C == 0 then (X | C) == X +_{nuw} C
5186 if (match(A, m_Or(m_Value(X), m_APInt(CA))) &&
5187 match(B, m_Or(m_Specific(X), m_APInt(CB)))) {
5188 KnownBits Known(CA->getBitWidth());
5189 computeKnownBits(X, Known, DL, Depth + 1, /*AC*/ nullptr,
5190 /*CxtI*/ nullptr, /*DT*/ nullptr);
5191 if (CA->isSubsetOf(Known.Zero) && CB->isSubsetOf(Known.Zero))
5199 const APInt *CLHS, *CRHS;
5200 if (MatchNUWAddsToSameValue(LHS, RHS, X, CLHS, CRHS))
5201 return CLHS->ule(*CRHS);
5208 /// Return true if "icmp Pred BLHS BRHS" is true whenever "icmp Pred
5209 /// ALHS ARHS" is true. Otherwise, return None.
5210 static Optional<bool>
5211 isImpliedCondOperands(CmpInst::Predicate Pred, const Value *ALHS,
5212 const Value *ARHS, const Value *BLHS, const Value *BRHS,
5213 const DataLayout &DL, unsigned Depth) {
5218 case CmpInst::ICMP_SLT:
5219 case CmpInst::ICMP_SLE:
5220 if (isTruePredicate(CmpInst::ICMP_SLE, BLHS, ALHS, DL, Depth) &&
5221 isTruePredicate(CmpInst::ICMP_SLE, ARHS, BRHS, DL, Depth))
5225 case CmpInst::ICMP_ULT:
5226 case CmpInst::ICMP_ULE:
5227 if (isTruePredicate(CmpInst::ICMP_ULE, BLHS, ALHS, DL, Depth) &&
5228 isTruePredicate(CmpInst::ICMP_ULE, ARHS, BRHS, DL, Depth))
5234 /// Return true if the operands of the two compares match. IsSwappedOps is true
5235 /// when the operands match, but are swapped.
5236 static bool isMatchingOps(const Value *ALHS, const Value *ARHS,
5237 const Value *BLHS, const Value *BRHS,
5238 bool &IsSwappedOps) {
5240 bool IsMatchingOps = (ALHS == BLHS && ARHS == BRHS);
5241 IsSwappedOps = (ALHS == BRHS && ARHS == BLHS);
5242 return IsMatchingOps || IsSwappedOps;
5245 /// Return true if "icmp1 APred X, Y" implies "icmp2 BPred X, Y" is true.
5246 /// Return false if "icmp1 APred X, Y" implies "icmp2 BPred X, Y" is false.
5247 /// Otherwise, return None if we can't infer anything.
5248 static Optional<bool> isImpliedCondMatchingOperands(CmpInst::Predicate APred,
5249 CmpInst::Predicate BPred,
5250 bool AreSwappedOps) {
5251 // Canonicalize the predicate as if the operands were not commuted.
5253 BPred = ICmpInst::getSwappedPredicate(BPred);
5255 if (CmpInst::isImpliedTrueByMatchingCmp(APred, BPred))
5257 if (CmpInst::isImpliedFalseByMatchingCmp(APred, BPred))
5263 /// Return true if "icmp APred X, C1" implies "icmp BPred X, C2" is true.
5264 /// Return false if "icmp APred X, C1" implies "icmp BPred X, C2" is false.
5265 /// Otherwise, return None if we can't infer anything.
5266 static Optional<bool>
5267 isImpliedCondMatchingImmOperands(CmpInst::Predicate APred,
5268 const ConstantInt *C1,
5269 CmpInst::Predicate BPred,
5270 const ConstantInt *C2) {
5271 ConstantRange DomCR =
5272 ConstantRange::makeExactICmpRegion(APred, C1->getValue());
5274 ConstantRange::makeAllowedICmpRegion(BPred, C2->getValue());
5275 ConstantRange Intersection = DomCR.intersectWith(CR);
5276 ConstantRange Difference = DomCR.difference(CR);
5277 if (Intersection.isEmptySet())
5279 if (Difference.isEmptySet())
5284 /// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
5285 /// false. Otherwise, return None if we can't infer anything.
5286 static Optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
5287 const ICmpInst *RHS,
5288 const DataLayout &DL, bool LHSIsTrue,
5290 Value *ALHS = LHS->getOperand(0);
5291 Value *ARHS = LHS->getOperand(1);
5292 // The rest of the logic assumes the LHS condition is true. If that's not the
5293 // case, invert the predicate to make it so.
5294 ICmpInst::Predicate APred =
5295 LHSIsTrue ? LHS->getPredicate() : LHS->getInversePredicate();
5297 Value *BLHS = RHS->getOperand(0);
5298 Value *BRHS = RHS->getOperand(1);
5299 ICmpInst::Predicate BPred = RHS->getPredicate();
5301 // Can we infer anything when the two compares have matching operands?
5303 if (isMatchingOps(ALHS, ARHS, BLHS, BRHS, AreSwappedOps)) {
5304 if (Optional<bool> Implication = isImpliedCondMatchingOperands(
5305 APred, BPred, AreSwappedOps))
5307 // No amount of additional analysis will infer the second condition, so
5312 // Can we infer anything when the LHS operands match and the RHS operands are
5313 // constants (not necessarily matching)?
5314 if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
5315 if (Optional<bool> Implication = isImpliedCondMatchingImmOperands(
5316 APred, cast<ConstantInt>(ARHS), BPred, cast<ConstantInt>(BRHS)))
5318 // No amount of additional analysis will infer the second condition, so
5324 return isImpliedCondOperands(APred, ALHS, ARHS, BLHS, BRHS, DL, Depth);
5328 /// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
5329 /// false. Otherwise, return None if we can't infer anything. We expect the
5330 /// RHS to be an icmp and the LHS to be an 'and' or an 'or' instruction.
5331 static Optional<bool> isImpliedCondAndOr(const BinaryOperator *LHS,
5332 const ICmpInst *RHS,
5333 const DataLayout &DL, bool LHSIsTrue,
5335 // The LHS must be an 'or' or an 'and' instruction.
5336 assert((LHS->getOpcode() == Instruction::And ||
5337 LHS->getOpcode() == Instruction::Or) &&
5338 "Expected LHS to be 'and' or 'or'.");
5340 assert(Depth <= MaxDepth && "Hit recursion limit");
5342 // If the result of an 'or' is false, then we know both legs of the 'or' are
5343 // false. Similarly, if the result of an 'and' is true, then we know both
5344 // legs of the 'and' are true.
5346 if ((!LHSIsTrue && match(LHS, m_Or(m_Value(ALHS), m_Value(ARHS)))) ||
5347 (LHSIsTrue && match(LHS, m_And(m_Value(ALHS), m_Value(ARHS))))) {
5348 // FIXME: Make this non-recursion.
5349 if (Optional<bool> Implication =
5350 isImpliedCondition(ALHS, RHS, DL, LHSIsTrue, Depth + 1))
5352 if (Optional<bool> Implication =
5353 isImpliedCondition(ARHS, RHS, DL, LHSIsTrue, Depth + 1))
5360 Optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
5361 const DataLayout &DL, bool LHSIsTrue,
5363 // Bail out when we hit the limit.
5364 if (Depth == MaxDepth)
5367 // A mismatch occurs when we compare a scalar cmp to a vector cmp, for
5369 if (LHS->getType() != RHS->getType())
5372 Type *OpTy = LHS->getType();
5373 assert(OpTy->isIntOrIntVectorTy(1) && "Expected integer type only!");
5375 // LHS ==> RHS by definition
5379 // FIXME: Extending the code below to handle vectors.
5380 if (OpTy->isVectorTy())
5383 assert(OpTy->isIntegerTy(1) && "implied by above");
5385 // Both LHS and RHS are icmps.
5386 const ICmpInst *LHSCmp = dyn_cast<ICmpInst>(LHS);
5387 const ICmpInst *RHSCmp = dyn_cast<ICmpInst>(RHS);
5388 if (LHSCmp && RHSCmp)
5389 return isImpliedCondICmps(LHSCmp, RHSCmp, DL, LHSIsTrue, Depth);
5391 // The LHS should be an 'or' or an 'and' instruction. We expect the RHS to be
5392 // an icmp. FIXME: Add support for and/or on the RHS.
5393 const BinaryOperator *LHSBO = dyn_cast<BinaryOperator>(LHS);
5394 if (LHSBO && RHSCmp) {
5395 if ((LHSBO->getOpcode() == Instruction::And ||
5396 LHSBO->getOpcode() == Instruction::Or))
5397 return isImpliedCondAndOr(LHSBO, RHSCmp, DL, LHSIsTrue, Depth);
5402 Optional<bool> llvm::isImpliedByDomCondition(const Value *Cond,
5403 const Instruction *ContextI,
5404 const DataLayout &DL) {
5405 assert(Cond->getType()->isIntOrIntVectorTy(1) && "Condition must be bool");
5406 if (!ContextI || !ContextI->getParent())
5409 // TODO: This is a poor/cheap way to determine dominance. Should we use a
5410 // dominator tree (eg, from a SimplifyQuery) instead?
5411 const BasicBlock *ContextBB = ContextI->getParent();
5412 const BasicBlock *PredBB = ContextBB->getSinglePredecessor();
5416 // We need a conditional branch in the predecessor.
5418 BasicBlock *TrueBB, *FalseBB;
5419 if (!match(PredBB->getTerminator(), m_Br(m_Value(PredCond), TrueBB, FalseBB)))
5422 // The branch should get simplified. Don't bother simplifying this condition.
5423 if (TrueBB == FalseBB)
5426 assert((TrueBB == ContextBB || FalseBB == ContextBB) &&
5427 "Predecessor block does not point to successor?");
5429 // Is this condition implied by the predecessor condition?
5430 bool CondIsTrue = TrueBB == ContextBB;
5431 return isImpliedCondition(PredCond, Cond, DL, CondIsTrue);