1 //===- BasicAliasAnalysis.cpp - Stateless Alias Analysis Impl -------------===//
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 defines the primary stateless implementation of the
11 // Alias Analysis interface that implements identities (two different
12 // globals cannot alias, etc), but does no stateful analysis.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Analysis/BasicAliasAnalysis.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/Analysis/AliasAnalysis.h"
20 #include "llvm/Analysis/AssumptionCache.h"
21 #include "llvm/Analysis/CFG.h"
22 #include "llvm/Analysis/CaptureTracking.h"
23 #include "llvm/Analysis/InstructionSimplify.h"
24 #include "llvm/Analysis/LoopInfo.h"
25 #include "llvm/Analysis/MemoryBuiltins.h"
26 #include "llvm/Analysis/ValueTracking.h"
27 #include "llvm/IR/Constants.h"
28 #include "llvm/IR/DataLayout.h"
29 #include "llvm/IR/DerivedTypes.h"
30 #include "llvm/IR/Dominators.h"
31 #include "llvm/IR/GlobalAlias.h"
32 #include "llvm/IR/GlobalVariable.h"
33 #include "llvm/IR/Instructions.h"
34 #include "llvm/IR/IntrinsicInst.h"
35 #include "llvm/IR/LLVMContext.h"
36 #include "llvm/IR/Operator.h"
37 #include "llvm/Pass.h"
38 #include "llvm/Support/ErrorHandling.h"
39 #include "llvm/Support/KnownBits.h"
42 #define DEBUG_TYPE "basicaa"
46 /// Enable analysis of recursive PHI nodes.
47 static cl::opt<bool> EnableRecPhiAnalysis("basicaa-recphi", cl::Hidden,
49 /// SearchLimitReached / SearchTimes shows how often the limit of
50 /// to decompose GEPs is reached. It will affect the precision
51 /// of basic alias analysis.
52 STATISTIC(SearchLimitReached, "Number of times the limit to "
53 "decompose GEPs is reached");
54 STATISTIC(SearchTimes, "Number of times a GEP is decomposed");
56 /// Cutoff after which to stop analysing a set of phi nodes potentially involved
57 /// in a cycle. Because we are analysing 'through' phi nodes, we need to be
58 /// careful with value equivalence. We use reachability to make sure a value
59 /// cannot be involved in a cycle.
60 const unsigned MaxNumPhiBBsValueReachabilityCheck = 20;
62 // The max limit of the search depth in DecomposeGEPExpression() and
63 // GetUnderlyingObject(), both functions need to use the same search
64 // depth otherwise the algorithm in aliasGEP will assert.
65 static const unsigned MaxLookupSearchDepth = 6;
67 bool BasicAAResult::invalidate(Function &F, const PreservedAnalyses &PA,
68 FunctionAnalysisManager::Invalidator &Inv) {
69 // We don't care if this analysis itself is preserved, it has no state. But
70 // we need to check that the analyses it depends on have been. Note that we
71 // may be created without handles to some analyses and in that case don't
73 if (Inv.invalidate<AssumptionAnalysis>(F, PA) ||
74 (DT && Inv.invalidate<DominatorTreeAnalysis>(F, PA)) ||
75 (LI && Inv.invalidate<LoopAnalysis>(F, PA)))
78 // Otherwise this analysis result remains valid.
82 //===----------------------------------------------------------------------===//
84 //===----------------------------------------------------------------------===//
86 /// Returns true if the pointer is to a function-local object that never
87 /// escapes from the function.
88 static bool isNonEscapingLocalObject(const Value *V) {
89 // If this is a local allocation, check to see if it escapes.
90 if (isa<AllocaInst>(V) || isNoAliasCall(V))
91 // Set StoreCaptures to True so that we can assume in our callers that the
92 // pointer is not the result of a load instruction. Currently
93 // PointerMayBeCaptured doesn't have any special analysis for the
94 // StoreCaptures=false case; if it did, our callers could be refined to be
96 return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
98 // If this is an argument that corresponds to a byval or noalias argument,
99 // then it has not escaped before entering the function. Check if it escapes
100 // inside the function.
101 if (const Argument *A = dyn_cast<Argument>(V))
102 if (A->hasByValAttr() || A->hasNoAliasAttr())
103 // Note even if the argument is marked nocapture, we still need to check
104 // for copies made inside the function. The nocapture attribute only
105 // specifies that there are no copies made that outlive the function.
106 return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
111 /// Returns true if the pointer is one which would have been considered an
112 /// escape by isNonEscapingLocalObject.
113 static bool isEscapeSource(const Value *V) {
114 if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
117 // The load case works because isNonEscapingLocalObject considers all
118 // stores to be escapes (it passes true for the StoreCaptures argument
119 // to PointerMayBeCaptured).
120 if (isa<LoadInst>(V))
126 /// Returns the size of the object specified by V or UnknownSize if unknown.
127 static uint64_t getObjectSize(const Value *V, const DataLayout &DL,
128 const TargetLibraryInfo &TLI,
129 bool RoundToAlign = false) {
132 Opts.RoundToAlign = RoundToAlign;
133 if (getObjectSize(V, Size, DL, &TLI, Opts))
135 return MemoryLocation::UnknownSize;
138 /// Returns true if we can prove that the object specified by V is smaller than
140 static bool isObjectSmallerThan(const Value *V, uint64_t Size,
141 const DataLayout &DL,
142 const TargetLibraryInfo &TLI) {
143 // Note that the meanings of the "object" are slightly different in the
144 // following contexts:
145 // c1: llvm::getObjectSize()
146 // c2: llvm.objectsize() intrinsic
147 // c3: isObjectSmallerThan()
148 // c1 and c2 share the same meaning; however, the meaning of "object" in c3
149 // refers to the "entire object".
151 // Consider this example:
152 // char *p = (char*)malloc(100)
155 // In the context of c1 and c2, the "object" pointed by q refers to the
156 // stretch of memory of q[0:19]. So, getObjectSize(q) should return 20.
158 // However, in the context of c3, the "object" refers to the chunk of memory
159 // being allocated. So, the "object" has 100 bytes, and q points to the middle
160 // the "object". In case q is passed to isObjectSmallerThan() as the 1st
161 // parameter, before the llvm::getObjectSize() is called to get the size of
162 // entire object, we should:
163 // - either rewind the pointer q to the base-address of the object in
164 // question (in this case rewind to p), or
165 // - just give up. It is up to caller to make sure the pointer is pointing
166 // to the base address the object.
168 // We go for 2nd option for simplicity.
169 if (!isIdentifiedObject(V))
172 // This function needs to use the aligned object size because we allow
173 // reads a bit past the end given sufficient alignment.
174 uint64_t ObjectSize = getObjectSize(V, DL, TLI, /*RoundToAlign*/ true);
176 return ObjectSize != MemoryLocation::UnknownSize && ObjectSize < Size;
179 /// Returns true if we can prove that the object specified by V has size Size.
180 static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
181 const TargetLibraryInfo &TLI) {
182 uint64_t ObjectSize = getObjectSize(V, DL, TLI);
183 return ObjectSize != MemoryLocation::UnknownSize && ObjectSize == Size;
186 //===----------------------------------------------------------------------===//
187 // GetElementPtr Instruction Decomposition and Analysis
188 //===----------------------------------------------------------------------===//
190 /// Analyzes the specified value as a linear expression: "A*V + B", where A and
191 /// B are constant integers.
193 /// Returns the scale and offset values as APInts and return V as a Value*, and
194 /// return whether we looked through any sign or zero extends. The incoming
195 /// Value is known to have IntegerType, and it may already be sign or zero
198 /// Note that this looks through extends, so the high bits may not be
199 /// represented in the result.
200 /*static*/ const Value *BasicAAResult::GetLinearExpression(
201 const Value *V, APInt &Scale, APInt &Offset, unsigned &ZExtBits,
202 unsigned &SExtBits, const DataLayout &DL, unsigned Depth,
203 AssumptionCache *AC, DominatorTree *DT, bool &NSW, bool &NUW) {
204 assert(V->getType()->isIntegerTy() && "Not an integer value");
206 // Limit our recursion depth.
213 if (const ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
214 // If it's a constant, just convert it to an offset and remove the variable.
215 // If we've been called recursively, the Offset bit width will be greater
216 // than the constant's (the Offset's always as wide as the outermost call),
217 // so we'll zext here and process any extension in the isa<SExtInst> &
218 // isa<ZExtInst> cases below.
219 Offset += Const->getValue().zextOrSelf(Offset.getBitWidth());
220 assert(Scale == 0 && "Constant values don't have a scale");
224 if (const BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
225 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
227 // If we've been called recursively, then Offset and Scale will be wider
228 // than the BOp operands. We'll always zext it here as we'll process sign
229 // extensions below (see the isa<SExtInst> / isa<ZExtInst> cases).
230 APInt RHS = RHSC->getValue().zextOrSelf(Offset.getBitWidth());
232 switch (BOp->getOpcode()) {
234 // We don't understand this instruction, so we can't decompose it any
239 case Instruction::Or:
240 // X|C == X+C if all the bits in C are unset in X. Otherwise we can't
242 if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), DL, 0, AC,
249 case Instruction::Add:
250 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
251 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
254 case Instruction::Sub:
255 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
256 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
259 case Instruction::Mul:
260 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
261 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
265 case Instruction::Shl:
266 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
267 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
268 Offset <<= RHS.getLimitedValue();
269 Scale <<= RHS.getLimitedValue();
270 // the semantics of nsw and nuw for left shifts don't match those of
271 // multiplications, so we won't propagate them.
276 if (isa<OverflowingBinaryOperator>(BOp)) {
277 NUW &= BOp->hasNoUnsignedWrap();
278 NSW &= BOp->hasNoSignedWrap();
284 // Since GEP indices are sign extended anyway, we don't care about the high
285 // bits of a sign or zero extended value - just scales and offsets. The
286 // extensions have to be consistent though.
287 if (isa<SExtInst>(V) || isa<ZExtInst>(V)) {
288 Value *CastOp = cast<CastInst>(V)->getOperand(0);
289 unsigned NewWidth = V->getType()->getPrimitiveSizeInBits();
290 unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
291 unsigned OldZExtBits = ZExtBits, OldSExtBits = SExtBits;
292 const Value *Result =
293 GetLinearExpression(CastOp, Scale, Offset, ZExtBits, SExtBits, DL,
294 Depth + 1, AC, DT, NSW, NUW);
296 // zext(zext(%x)) == zext(%x), and similarly for sext; we'll handle this
297 // by just incrementing the number of bits we've extended by.
298 unsigned ExtendedBy = NewWidth - SmallWidth;
300 if (isa<SExtInst>(V) && ZExtBits == 0) {
301 // sext(sext(%x, a), b) == sext(%x, a + b)
304 // We haven't sign-wrapped, so it's valid to decompose sext(%x + c)
305 // into sext(%x) + sext(c). We'll sext the Offset ourselves:
306 unsigned OldWidth = Offset.getBitWidth();
307 Offset = Offset.trunc(SmallWidth).sext(NewWidth).zextOrSelf(OldWidth);
309 // We may have signed-wrapped, so don't decompose sext(%x + c) into
310 // sext(%x) + sext(c)
314 ZExtBits = OldZExtBits;
315 SExtBits = OldSExtBits;
317 SExtBits += ExtendedBy;
319 // sext(zext(%x, a), b) = zext(zext(%x, a), b) = zext(%x, a + b)
322 // We may have unsigned-wrapped, so don't decompose zext(%x + c) into
323 // zext(%x) + zext(c)
327 ZExtBits = OldZExtBits;
328 SExtBits = OldSExtBits;
330 ZExtBits += ExtendedBy;
341 /// To ensure a pointer offset fits in an integer of size PointerSize
342 /// (in bits) when that size is smaller than 64. This is an issue in
343 /// particular for 32b programs with negative indices that rely on two's
344 /// complement wrap-arounds for precise alias information.
345 static int64_t adjustToPointerSize(int64_t Offset, unsigned PointerSize) {
346 assert(PointerSize <= 64 && "Invalid PointerSize!");
347 unsigned ShiftBits = 64 - PointerSize;
348 return (int64_t)((uint64_t)Offset << ShiftBits) >> ShiftBits;
351 /// If V is a symbolic pointer expression, decompose it into a base pointer
352 /// with a constant offset and a number of scaled symbolic offsets.
354 /// The scaled symbolic offsets (represented by pairs of a Value* and a scale
355 /// in the VarIndices vector) are Value*'s that are known to be scaled by the
356 /// specified amount, but which may have other unrepresented high bits. As
357 /// such, the gep cannot necessarily be reconstructed from its decomposed form.
359 /// When DataLayout is around, this function is capable of analyzing everything
360 /// that GetUnderlyingObject can look through. To be able to do that
361 /// GetUnderlyingObject and DecomposeGEPExpression must use the same search
362 /// depth (MaxLookupSearchDepth). When DataLayout not is around, it just looks
363 /// through pointer casts.
364 bool BasicAAResult::DecomposeGEPExpression(const Value *V,
365 DecomposedGEP &Decomposed, const DataLayout &DL, AssumptionCache *AC,
367 // Limit recursion depth to limit compile time in crazy cases.
368 unsigned MaxLookup = MaxLookupSearchDepth;
371 Decomposed.StructOffset = 0;
372 Decomposed.OtherOffset = 0;
373 Decomposed.VarIndices.clear();
375 // See if this is a bitcast or GEP.
376 const Operator *Op = dyn_cast<Operator>(V);
378 // The only non-operator case we can handle are GlobalAliases.
379 if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
380 if (!GA->isInterposable()) {
381 V = GA->getAliasee();
389 if (Op->getOpcode() == Instruction::BitCast ||
390 Op->getOpcode() == Instruction::AddrSpaceCast) {
391 V = Op->getOperand(0);
395 const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
397 if (auto CS = ImmutableCallSite(V))
398 if (const Value *RV = CS.getReturnedArgOperand()) {
403 // If it's not a GEP, hand it off to SimplifyInstruction to see if it
404 // can come up with something. This matches what GetUnderlyingObject does.
405 if (const Instruction *I = dyn_cast<Instruction>(V))
406 // TODO: Get a DominatorTree and AssumptionCache and use them here
407 // (these are both now available in this function, but this should be
408 // updated when GetUnderlyingObject is updated). TLI should be
410 if (const Value *Simplified =
411 SimplifyInstruction(const_cast<Instruction *>(I), DL)) {
420 // Don't attempt to analyze GEPs over unsized objects.
421 if (!GEPOp->getSourceElementType()->isSized()) {
426 unsigned AS = GEPOp->getPointerAddressSpace();
427 // Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
428 gep_type_iterator GTI = gep_type_begin(GEPOp);
429 unsigned PointerSize = DL.getPointerSizeInBits(AS);
430 // Assume all GEP operands are constants until proven otherwise.
431 bool GepHasConstantOffset = true;
432 for (User::const_op_iterator I = GEPOp->op_begin() + 1, E = GEPOp->op_end();
433 I != E; ++I, ++GTI) {
434 const Value *Index = *I;
435 // Compute the (potentially symbolic) offset in bytes for this index.
436 if (StructType *STy = GTI.getStructTypeOrNull()) {
437 // For a struct, add the member offset.
438 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
442 Decomposed.StructOffset +=
443 DL.getStructLayout(STy)->getElementOffset(FieldNo);
447 // For an array/pointer, add the element offset, explicitly scaled.
448 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
451 Decomposed.OtherOffset +=
452 DL.getTypeAllocSize(GTI.getIndexedType()) * CIdx->getSExtValue();
456 GepHasConstantOffset = false;
458 uint64_t Scale = DL.getTypeAllocSize(GTI.getIndexedType());
459 unsigned ZExtBits = 0, SExtBits = 0;
461 // If the integer type is smaller than the pointer size, it is implicitly
462 // sign extended to pointer size.
463 unsigned Width = Index->getType()->getIntegerBitWidth();
464 if (PointerSize > Width)
465 SExtBits += PointerSize - Width;
467 // Use GetLinearExpression to decompose the index into a C1*V+C2 form.
468 APInt IndexScale(Width, 0), IndexOffset(Width, 0);
469 bool NSW = true, NUW = true;
470 Index = GetLinearExpression(Index, IndexScale, IndexOffset, ZExtBits,
471 SExtBits, DL, 0, AC, DT, NSW, NUW);
473 // The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale.
474 // This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.
475 Decomposed.OtherOffset += IndexOffset.getSExtValue() * Scale;
476 Scale *= IndexScale.getSExtValue();
478 // If we already had an occurrence of this index variable, merge this
479 // scale into it. For example, we want to handle:
480 // A[x][x] -> x*16 + x*4 -> x*20
481 // This also ensures that 'x' only appears in the index list once.
482 for (unsigned i = 0, e = Decomposed.VarIndices.size(); i != e; ++i) {
483 if (Decomposed.VarIndices[i].V == Index &&
484 Decomposed.VarIndices[i].ZExtBits == ZExtBits &&
485 Decomposed.VarIndices[i].SExtBits == SExtBits) {
486 Scale += Decomposed.VarIndices[i].Scale;
487 Decomposed.VarIndices.erase(Decomposed.VarIndices.begin() + i);
492 // Make sure that we have a scale that makes sense for this target's
494 Scale = adjustToPointerSize(Scale, PointerSize);
497 VariableGEPIndex Entry = {Index, ZExtBits, SExtBits,
498 static_cast<int64_t>(Scale)};
499 Decomposed.VarIndices.push_back(Entry);
503 // Take care of wrap-arounds
504 if (GepHasConstantOffset) {
505 Decomposed.StructOffset =
506 adjustToPointerSize(Decomposed.StructOffset, PointerSize);
507 Decomposed.OtherOffset =
508 adjustToPointerSize(Decomposed.OtherOffset, PointerSize);
511 // Analyze the base pointer next.
512 V = GEPOp->getOperand(0);
513 } while (--MaxLookup);
515 // If the chain of expressions is too deep, just return early.
517 SearchLimitReached++;
521 /// Returns whether the given pointer value points to memory that is local to
522 /// the function, with global constants being considered local to all
524 bool BasicAAResult::pointsToConstantMemory(const MemoryLocation &Loc,
526 assert(Visited.empty() && "Visited must be cleared after use!");
528 unsigned MaxLookup = 8;
529 SmallVector<const Value *, 16> Worklist;
530 Worklist.push_back(Loc.Ptr);
532 const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), DL);
533 if (!Visited.insert(V).second) {
535 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
538 // An alloca instruction defines local memory.
539 if (OrLocal && isa<AllocaInst>(V))
542 // A global constant counts as local memory for our purposes.
543 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
544 // Note: this doesn't require GV to be "ODR" because it isn't legal for a
545 // global to be marked constant in some modules and non-constant in
546 // others. GV may even be a declaration, not a definition.
547 if (!GV->isConstant()) {
549 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
554 // If both select values point to local memory, then so does the select.
555 if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
556 Worklist.push_back(SI->getTrueValue());
557 Worklist.push_back(SI->getFalseValue());
561 // If all values incoming to a phi node point to local memory, then so does
563 if (const PHINode *PN = dyn_cast<PHINode>(V)) {
564 // Don't bother inspecting phi nodes with many operands.
565 if (PN->getNumIncomingValues() > MaxLookup) {
567 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
569 for (Value *IncValue : PN->incoming_values())
570 Worklist.push_back(IncValue);
574 // Otherwise be conservative.
576 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
578 } while (!Worklist.empty() && --MaxLookup);
581 return Worklist.empty();
584 /// Returns the behavior when calling the given call site.
585 FunctionModRefBehavior BasicAAResult::getModRefBehavior(ImmutableCallSite CS) {
586 if (CS.doesNotAccessMemory())
587 // Can't do better than this.
588 return FMRB_DoesNotAccessMemory;
590 FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
592 // If the callsite knows it only reads memory, don't return worse
594 if (CS.onlyReadsMemory())
595 Min = FMRB_OnlyReadsMemory;
596 else if (CS.doesNotReadMemory())
597 Min = FMRB_DoesNotReadMemory;
599 if (CS.onlyAccessesArgMemory())
600 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
602 // If CS has operand bundles then aliasing attributes from the function it
603 // calls do not directly apply to the CallSite. This can be made more
604 // precise in the future.
605 if (!CS.hasOperandBundles())
606 if (const Function *F = CS.getCalledFunction())
608 FunctionModRefBehavior(Min & getBestAAResults().getModRefBehavior(F));
613 /// Returns the behavior when calling the given function. For use when the call
614 /// site is not known.
615 FunctionModRefBehavior BasicAAResult::getModRefBehavior(const Function *F) {
616 // If the function declares it doesn't access memory, we can't do better.
617 if (F->doesNotAccessMemory())
618 return FMRB_DoesNotAccessMemory;
620 FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
622 // If the function declares it only reads memory, go with that.
623 if (F->onlyReadsMemory())
624 Min = FMRB_OnlyReadsMemory;
625 else if (F->doesNotReadMemory())
626 Min = FMRB_DoesNotReadMemory;
628 if (F->onlyAccessesArgMemory())
629 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
630 else if (F->onlyAccessesInaccessibleMemory())
631 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesInaccessibleMem);
632 else if (F->onlyAccessesInaccessibleMemOrArgMem())
633 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesInaccessibleOrArgMem);
638 /// Returns true if this is a writeonly (i.e Mod only) parameter.
639 static bool isWriteOnlyParam(ImmutableCallSite CS, unsigned ArgIdx,
640 const TargetLibraryInfo &TLI) {
641 if (CS.paramHasAttr(ArgIdx, Attribute::WriteOnly))
644 // We can bound the aliasing properties of memset_pattern16 just as we can
645 // for memcpy/memset. This is particularly important because the
646 // LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
647 // whenever possible.
648 // FIXME Consider handling this in InferFunctionAttr.cpp together with other
651 if (CS.getCalledFunction() && TLI.getLibFunc(*CS.getCalledFunction(), F) &&
652 F == LibFunc_memset_pattern16 && TLI.has(F))
656 // TODO: memset_pattern4, memset_pattern8
657 // TODO: _chk variants
658 // TODO: strcmp, strcpy
663 ModRefInfo BasicAAResult::getArgModRefInfo(ImmutableCallSite CS,
666 // Checking for known builtin intrinsics and target library functions.
667 if (isWriteOnlyParam(CS, ArgIdx, TLI))
670 if (CS.paramHasAttr(ArgIdx, Attribute::ReadOnly))
673 if (CS.paramHasAttr(ArgIdx, Attribute::ReadNone))
676 return AAResultBase::getArgModRefInfo(CS, ArgIdx);
679 static bool isIntrinsicCall(ImmutableCallSite CS, Intrinsic::ID IID) {
680 const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
681 return II && II->getIntrinsicID() == IID;
685 static const Function *getParent(const Value *V) {
686 if (const Instruction *inst = dyn_cast<Instruction>(V)) {
687 if (!inst->getParent())
689 return inst->getParent()->getParent();
692 if (const Argument *arg = dyn_cast<Argument>(V))
693 return arg->getParent();
698 static bool notDifferentParent(const Value *O1, const Value *O2) {
700 const Function *F1 = getParent(O1);
701 const Function *F2 = getParent(O2);
703 return !F1 || !F2 || F1 == F2;
707 AliasResult BasicAAResult::alias(const MemoryLocation &LocA,
708 const MemoryLocation &LocB) {
709 assert(notDifferentParent(LocA.Ptr, LocB.Ptr) &&
710 "BasicAliasAnalysis doesn't support interprocedural queries.");
712 // If we have a directly cached entry for these locations, we have recursed
713 // through this once, so just return the cached results. Notably, when this
714 // happens, we don't clear the cache.
715 auto CacheIt = AliasCache.find(LocPair(LocA, LocB));
716 if (CacheIt != AliasCache.end())
717 return CacheIt->second;
719 AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.AATags, LocB.Ptr,
720 LocB.Size, LocB.AATags);
721 // AliasCache rarely has more than 1 or 2 elements, always use
722 // shrink_and_clear so it quickly returns to the inline capacity of the
723 // SmallDenseMap if it ever grows larger.
724 // FIXME: This should really be shrink_to_inline_capacity_and_clear().
725 AliasCache.shrink_and_clear();
726 VisitedPhiBBs.clear();
730 /// Checks to see if the specified callsite can clobber the specified memory
733 /// Since we only look at local properties of this function, we really can't
734 /// say much about this query. We do, however, use simple "address taken"
735 /// analysis on local objects.
736 ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS,
737 const MemoryLocation &Loc) {
738 assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
739 "AliasAnalysis query involving multiple functions!");
741 const Value *Object = GetUnderlyingObject(Loc.Ptr, DL);
743 // If this is a tail call and Loc.Ptr points to a stack location, we know that
744 // the tail call cannot access or modify the local stack.
745 // We cannot exclude byval arguments here; these belong to the caller of
746 // the current function not to the current function, and a tail callee
747 // may reference them.
748 if (isa<AllocaInst>(Object))
749 if (const CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
750 if (CI->isTailCall())
753 // If the pointer is to a locally allocated object that does not escape,
754 // then the call can not mod/ref the pointer unless the call takes the pointer
755 // as an argument, and itself doesn't capture it.
756 if (!isa<Constant>(Object) && CS.getInstruction() != Object &&
757 isNonEscapingLocalObject(Object)) {
759 // Optimistically assume that call doesn't touch Object and check this
760 // assumption in the following loop.
761 ModRefInfo Result = MRI_NoModRef;
763 unsigned OperandNo = 0;
764 for (auto CI = CS.data_operands_begin(), CE = CS.data_operands_end();
765 CI != CE; ++CI, ++OperandNo) {
766 // Only look at the no-capture or byval pointer arguments. If this
767 // pointer were passed to arguments that were neither of these, then it
768 // couldn't be no-capture.
769 if (!(*CI)->getType()->isPointerTy() ||
770 (!CS.doesNotCapture(OperandNo) &&
771 OperandNo < CS.getNumArgOperands() && !CS.isByValArgument(OperandNo)))
774 // Call doesn't access memory through this operand, so we don't care
775 // if it aliases with Object.
776 if (CS.doesNotAccessMemory(OperandNo))
779 // If this is a no-capture pointer argument, see if we can tell that it
780 // is impossible to alias the pointer we're checking.
782 getBestAAResults().alias(MemoryLocation(*CI), MemoryLocation(Object));
784 // Operand doesnt alias 'Object', continue looking for other aliases
787 // Operand aliases 'Object', but call doesn't modify it. Strengthen
788 // initial assumption and keep looking in case if there are more aliases.
789 if (CS.onlyReadsMemory(OperandNo)) {
790 Result = static_cast<ModRefInfo>(Result | MRI_Ref);
793 // Operand aliases 'Object' but call only writes into it.
794 if (CS.doesNotReadMemory(OperandNo)) {
795 Result = static_cast<ModRefInfo>(Result | MRI_Mod);
798 // This operand aliases 'Object' and call reads and writes into it.
803 // Early return if we improved mod ref information
804 if (Result != MRI_ModRef)
808 // If the CallSite is to malloc or calloc, we can assume that it doesn't
809 // modify any IR visible value. This is only valid because we assume these
810 // routines do not read values visible in the IR. TODO: Consider special
811 // casing realloc and strdup routines which access only their arguments as
812 // well. Or alternatively, replace all of this with inaccessiblememonly once
813 // that's implemented fully.
814 auto *Inst = CS.getInstruction();
815 if (isMallocOrCallocLikeFn(Inst, &TLI)) {
816 // Be conservative if the accessed pointer may alias the allocation -
817 // fallback to the generic handling below.
818 if (getBestAAResults().alias(MemoryLocation(Inst), Loc) == NoAlias)
822 // The semantics of memcpy intrinsics forbid overlap between their respective
823 // operands, i.e., source and destination of any given memcpy must no-alias.
824 // If Loc must-aliases either one of these two locations, then it necessarily
825 // no-aliases the other.
826 if (auto *Inst = dyn_cast<MemCpyInst>(CS.getInstruction())) {
827 AliasResult SrcAA, DestAA;
829 if ((SrcAA = getBestAAResults().alias(MemoryLocation::getForSource(Inst),
831 // Loc is exactly the memcpy source thus disjoint from memcpy dest.
833 if ((DestAA = getBestAAResults().alias(MemoryLocation::getForDest(Inst),
835 // The converse case.
838 // It's also possible for Loc to alias both src and dest, or neither.
839 ModRefInfo rv = MRI_NoModRef;
840 if (SrcAA != NoAlias)
841 rv = static_cast<ModRefInfo>(rv | MRI_Ref);
842 if (DestAA != NoAlias)
843 rv = static_cast<ModRefInfo>(rv | MRI_Mod);
847 // While the assume intrinsic is marked as arbitrarily writing so that
848 // proper control dependencies will be maintained, it never aliases any
849 // particular memory location.
850 if (isIntrinsicCall(CS, Intrinsic::assume))
853 // Like assumes, guard intrinsics are also marked as arbitrarily writing so
854 // that proper control dependencies are maintained but they never mods any
855 // particular memory location.
857 // *Unlike* assumes, guard intrinsics are modeled as reading memory since the
858 // heap state at the point the guard is issued needs to be consistent in case
859 // the guard invokes the "deopt" continuation.
860 if (isIntrinsicCall(CS, Intrinsic::experimental_guard))
863 // Like assumes, invariant.start intrinsics were also marked as arbitrarily
864 // writing so that proper control dependencies are maintained but they never
865 // mod any particular memory location visible to the IR.
866 // *Unlike* assumes (which are now modeled as NoModRef), invariant.start
867 // intrinsic is now modeled as reading memory. This prevents hoisting the
868 // invariant.start intrinsic over stores. Consider:
871 // invariant_start(ptr)
875 // This cannot be transformed to:
878 // invariant_start(ptr)
883 // The transformation will cause the second store to be ignored (based on
884 // rules of invariant.start) and print 40, while the first program always
886 if (isIntrinsicCall(CS, Intrinsic::invariant_start))
889 // The AAResultBase base class has some smarts, lets use them.
890 return AAResultBase::getModRefInfo(CS, Loc);
893 ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS1,
894 ImmutableCallSite CS2) {
895 // While the assume intrinsic is marked as arbitrarily writing so that
896 // proper control dependencies will be maintained, it never aliases any
897 // particular memory location.
898 if (isIntrinsicCall(CS1, Intrinsic::assume) ||
899 isIntrinsicCall(CS2, Intrinsic::assume))
902 // Like assumes, guard intrinsics are also marked as arbitrarily writing so
903 // that proper control dependencies are maintained but they never mod any
904 // particular memory location.
906 // *Unlike* assumes, guard intrinsics are modeled as reading memory since the
907 // heap state at the point the guard is issued needs to be consistent in case
908 // the guard invokes the "deopt" continuation.
910 // NB! This function is *not* commutative, so we specical case two
911 // possibilities for guard intrinsics.
913 if (isIntrinsicCall(CS1, Intrinsic::experimental_guard))
914 return getModRefBehavior(CS2) & MRI_Mod ? MRI_Ref : MRI_NoModRef;
916 if (isIntrinsicCall(CS2, Intrinsic::experimental_guard))
917 return getModRefBehavior(CS1) & MRI_Mod ? MRI_Mod : MRI_NoModRef;
919 // The AAResultBase base class has some smarts, lets use them.
920 return AAResultBase::getModRefInfo(CS1, CS2);
923 /// Provide ad-hoc rules to disambiguate accesses through two GEP operators,
924 /// both having the exact same pointer operand.
925 static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
927 const GEPOperator *GEP2,
929 const DataLayout &DL) {
931 assert(GEP1->getPointerOperand()->stripPointerCastsAndBarriers() ==
932 GEP2->getPointerOperand()->stripPointerCastsAndBarriers() &&
933 GEP1->getPointerOperandType() == GEP2->getPointerOperandType() &&
934 "Expected GEPs with the same pointer operand");
936 // Try to determine whether GEP1 and GEP2 index through arrays, into structs,
937 // such that the struct field accesses provably cannot alias.
938 // We also need at least two indices (the pointer, and the struct field).
939 if (GEP1->getNumIndices() != GEP2->getNumIndices() ||
940 GEP1->getNumIndices() < 2)
943 // If we don't know the size of the accesses through both GEPs, we can't
944 // determine whether the struct fields accessed can't alias.
945 if (V1Size == MemoryLocation::UnknownSize ||
946 V2Size == MemoryLocation::UnknownSize)
950 dyn_cast<ConstantInt>(GEP1->getOperand(GEP1->getNumOperands() - 1));
952 dyn_cast<ConstantInt>(GEP2->getOperand(GEP2->getNumOperands() - 1));
954 // If the last (struct) indices are constants and are equal, the other indices
955 // might be also be dynamically equal, so the GEPs can alias.
956 if (C1 && C2 && C1->getSExtValue() == C2->getSExtValue())
959 // Find the last-indexed type of the GEP, i.e., the type you'd get if
960 // you stripped the last index.
961 // On the way, look at each indexed type. If there's something other
962 // than an array, different indices can lead to different final types.
963 SmallVector<Value *, 8> IntermediateIndices;
965 // Insert the first index; we don't need to check the type indexed
966 // through it as it only drops the pointer indirection.
967 assert(GEP1->getNumIndices() > 1 && "Not enough GEP indices to examine");
968 IntermediateIndices.push_back(GEP1->getOperand(1));
970 // Insert all the remaining indices but the last one.
971 // Also, check that they all index through arrays.
972 for (unsigned i = 1, e = GEP1->getNumIndices() - 1; i != e; ++i) {
973 if (!isa<ArrayType>(GetElementPtrInst::getIndexedType(
974 GEP1->getSourceElementType(), IntermediateIndices)))
976 IntermediateIndices.push_back(GEP1->getOperand(i + 1));
979 auto *Ty = GetElementPtrInst::getIndexedType(
980 GEP1->getSourceElementType(), IntermediateIndices);
981 StructType *LastIndexedStruct = dyn_cast<StructType>(Ty);
983 if (isa<SequentialType>(Ty)) {
985 // - both GEPs begin indexing from the exact same pointer;
986 // - the last indices in both GEPs are constants, indexing into a sequential
987 // type (array or pointer);
988 // - both GEPs only index through arrays prior to that.
990 // Because array indices greater than the number of elements are valid in
991 // GEPs, unless we know the intermediate indices are identical between
992 // GEP1 and GEP2 we cannot guarantee that the last indexed arrays don't
993 // partially overlap. We also need to check that the loaded size matches
994 // the element size, otherwise we could still have overlap.
995 const uint64_t ElementSize =
996 DL.getTypeStoreSize(cast<SequentialType>(Ty)->getElementType());
997 if (V1Size != ElementSize || V2Size != ElementSize)
1000 for (unsigned i = 0, e = GEP1->getNumIndices() - 1; i != e; ++i)
1001 if (GEP1->getOperand(i + 1) != GEP2->getOperand(i + 1))
1004 // Now we know that the array/pointer that GEP1 indexes into and that
1005 // that GEP2 indexes into must either precisely overlap or be disjoint.
1006 // Because they cannot partially overlap and because fields in an array
1007 // cannot overlap, if we can prove the final indices are different between
1008 // GEP1 and GEP2, we can conclude GEP1 and GEP2 don't alias.
1010 // If the last indices are constants, we've already checked they don't
1011 // equal each other so we can exit early.
1014 if (isKnownNonEqual(GEP1->getOperand(GEP1->getNumOperands() - 1),
1015 GEP2->getOperand(GEP2->getNumOperands() - 1),
1019 } else if (!LastIndexedStruct || !C1 || !C2) {
1024 // - both GEPs begin indexing from the exact same pointer;
1025 // - the last indices in both GEPs are constants, indexing into a struct;
1026 // - said indices are different, hence, the pointed-to fields are different;
1027 // - both GEPs only index through arrays prior to that.
1029 // This lets us determine that the struct that GEP1 indexes into and the
1030 // struct that GEP2 indexes into must either precisely overlap or be
1031 // completely disjoint. Because they cannot partially overlap, indexing into
1032 // different non-overlapping fields of the struct will never alias.
1034 // Therefore, the only remaining thing needed to show that both GEPs can't
1035 // alias is that the fields are not overlapping.
1036 const StructLayout *SL = DL.getStructLayout(LastIndexedStruct);
1037 const uint64_t StructSize = SL->getSizeInBytes();
1038 const uint64_t V1Off = SL->getElementOffset(C1->getZExtValue());
1039 const uint64_t V2Off = SL->getElementOffset(C2->getZExtValue());
1041 auto EltsDontOverlap = [StructSize](uint64_t V1Off, uint64_t V1Size,
1042 uint64_t V2Off, uint64_t V2Size) {
1043 return V1Off < V2Off && V1Off + V1Size <= V2Off &&
1044 ((V2Off + V2Size <= StructSize) ||
1045 (V2Off + V2Size - StructSize <= V1Off));
1048 if (EltsDontOverlap(V1Off, V1Size, V2Off, V2Size) ||
1049 EltsDontOverlap(V2Off, V2Size, V1Off, V1Size))
1055 // If a we have (a) a GEP and (b) a pointer based on an alloca, and the
1056 // beginning of the object the GEP points would have a negative offset with
1057 // repsect to the alloca, that means the GEP can not alias pointer (b).
1058 // Note that the pointer based on the alloca may not be a GEP. For
1059 // example, it may be the alloca itself.
1060 // The same applies if (b) is based on a GlobalVariable. Note that just being
1061 // based on isIdentifiedObject() is not enough - we need an identified object
1062 // that does not permit access to negative offsets. For example, a negative
1063 // offset from a noalias argument or call can be inbounds w.r.t the actual
1064 // underlying object.
1066 // For example, consider:
1068 // struct { int f0, int f1, ...} foo;
1070 // foo* random = bar(alloca);
1071 // int *f0 = &alloca.f0
1072 // int *f1 = &random->f1;
1074 // Which is lowered, approximately, to:
1076 // %alloca = alloca %struct.foo
1077 // %random = call %struct.foo* @random(%struct.foo* %alloca)
1078 // %f0 = getelementptr inbounds %struct, %struct.foo* %alloca, i32 0, i32 0
1079 // %f1 = getelementptr inbounds %struct, %struct.foo* %random, i32 0, i32 1
1081 // Assume %f1 and %f0 alias. Then %f1 would point into the object allocated
1082 // by %alloca. Since the %f1 GEP is inbounds, that means %random must also
1083 // point into the same object. But since %f0 points to the beginning of %alloca,
1084 // the highest %f1 can be is (%alloca + 3). This means %random can not be higher
1085 // than (%alloca - 1), and so is not inbounds, a contradiction.
1086 bool BasicAAResult::isGEPBaseAtNegativeOffset(const GEPOperator *GEPOp,
1087 const DecomposedGEP &DecompGEP, const DecomposedGEP &DecompObject,
1088 uint64_t ObjectAccessSize) {
1089 // If the object access size is unknown, or the GEP isn't inbounds, bail.
1090 if (ObjectAccessSize == MemoryLocation::UnknownSize || !GEPOp->isInBounds())
1093 // We need the object to be an alloca or a globalvariable, and want to know
1094 // the offset of the pointer from the object precisely, so no variable
1095 // indices are allowed.
1096 if (!(isa<AllocaInst>(DecompObject.Base) ||
1097 isa<GlobalVariable>(DecompObject.Base)) ||
1098 !DecompObject.VarIndices.empty())
1101 int64_t ObjectBaseOffset = DecompObject.StructOffset +
1102 DecompObject.OtherOffset;
1104 // If the GEP has no variable indices, we know the precise offset
1105 // from the base, then use it. If the GEP has variable indices, we're in
1106 // a bit more trouble: we can't count on the constant offsets that come
1107 // from non-struct sources, since these can be "rewound" by a negative
1108 // variable offset. So use only offsets that came from structs.
1109 int64_t GEPBaseOffset = DecompGEP.StructOffset;
1110 if (DecompGEP.VarIndices.empty())
1111 GEPBaseOffset += DecompGEP.OtherOffset;
1113 return (GEPBaseOffset >= ObjectBaseOffset + (int64_t)ObjectAccessSize);
1116 /// Provides a bunch of ad-hoc rules to disambiguate a GEP instruction against
1117 /// another pointer.
1119 /// We know that V1 is a GEP, but we don't know anything about V2.
1120 /// UnderlyingV1 is GetUnderlyingObject(GEP1, DL), UnderlyingV2 is the same for
1122 AliasResult BasicAAResult::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
1123 const AAMDNodes &V1AAInfo, const Value *V2,
1124 uint64_t V2Size, const AAMDNodes &V2AAInfo,
1125 const Value *UnderlyingV1,
1126 const Value *UnderlyingV2) {
1127 DecomposedGEP DecompGEP1, DecompGEP2;
1128 bool GEP1MaxLookupReached =
1129 DecomposeGEPExpression(GEP1, DecompGEP1, DL, &AC, DT);
1130 bool GEP2MaxLookupReached =
1131 DecomposeGEPExpression(V2, DecompGEP2, DL, &AC, DT);
1133 int64_t GEP1BaseOffset = DecompGEP1.StructOffset + DecompGEP1.OtherOffset;
1134 int64_t GEP2BaseOffset = DecompGEP2.StructOffset + DecompGEP2.OtherOffset;
1136 assert(DecompGEP1.Base == UnderlyingV1 && DecompGEP2.Base == UnderlyingV2 &&
1137 "DecomposeGEPExpression returned a result different from "
1138 "GetUnderlyingObject");
1140 // If the GEP's offset relative to its base is such that the base would
1141 // fall below the start of the object underlying V2, then the GEP and V2
1143 if (!GEP1MaxLookupReached && !GEP2MaxLookupReached &&
1144 isGEPBaseAtNegativeOffset(GEP1, DecompGEP1, DecompGEP2, V2Size))
1146 // If we have two gep instructions with must-alias or not-alias'ing base
1147 // pointers, figure out if the indexes to the GEP tell us anything about the
1149 if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
1150 // Check for the GEP base being at a negative offset, this time in the other
1152 if (!GEP1MaxLookupReached && !GEP2MaxLookupReached &&
1153 isGEPBaseAtNegativeOffset(GEP2, DecompGEP2, DecompGEP1, V1Size))
1155 // Do the base pointers alias?
1156 AliasResult BaseAlias =
1157 aliasCheck(UnderlyingV1, MemoryLocation::UnknownSize, AAMDNodes(),
1158 UnderlyingV2, MemoryLocation::UnknownSize, AAMDNodes());
1160 // Check for geps of non-aliasing underlying pointers where the offsets are
1162 if ((BaseAlias == MayAlias) && V1Size == V2Size) {
1163 // Do the base pointers alias assuming type and size.
1164 AliasResult PreciseBaseAlias = aliasCheck(UnderlyingV1, V1Size, V1AAInfo,
1165 UnderlyingV2, V2Size, V2AAInfo);
1166 if (PreciseBaseAlias == NoAlias) {
1167 // See if the computed offset from the common pointer tells us about the
1168 // relation of the resulting pointer.
1169 // If the max search depth is reached the result is undefined
1170 if (GEP2MaxLookupReached || GEP1MaxLookupReached)
1174 if (GEP1BaseOffset == GEP2BaseOffset &&
1175 DecompGEP1.VarIndices == DecompGEP2.VarIndices)
1180 // If we get a No or May, then return it immediately, no amount of analysis
1181 // will improve this situation.
1182 if (BaseAlias != MustAlias)
1185 // Otherwise, we have a MustAlias. Since the base pointers alias each other
1186 // exactly, see if the computed offset from the common pointer tells us
1187 // about the relation of the resulting pointer.
1188 // If we know the two GEPs are based off of the exact same pointer (and not
1189 // just the same underlying object), see if that tells us anything about
1190 // the resulting pointers.
1191 if (GEP1->getPointerOperand()->stripPointerCastsAndBarriers() ==
1192 GEP2->getPointerOperand()->stripPointerCastsAndBarriers() &&
1193 GEP1->getPointerOperandType() == GEP2->getPointerOperandType()) {
1194 AliasResult R = aliasSameBasePointerGEPs(GEP1, V1Size, GEP2, V2Size, DL);
1195 // If we couldn't find anything interesting, don't abandon just yet.
1200 // If the max search depth is reached, the result is undefined
1201 if (GEP2MaxLookupReached || GEP1MaxLookupReached)
1204 // Subtract the GEP2 pointer from the GEP1 pointer to find out their
1205 // symbolic difference.
1206 GEP1BaseOffset -= GEP2BaseOffset;
1207 GetIndexDifference(DecompGEP1.VarIndices, DecompGEP2.VarIndices);
1210 // Check to see if these two pointers are related by the getelementptr
1211 // instruction. If one pointer is a GEP with a non-zero index of the other
1212 // pointer, we know they cannot alias.
1214 // If both accesses are unknown size, we can't do anything useful here.
1215 if (V1Size == MemoryLocation::UnknownSize &&
1216 V2Size == MemoryLocation::UnknownSize)
1219 AliasResult R = aliasCheck(UnderlyingV1, MemoryLocation::UnknownSize,
1220 AAMDNodes(), V2, MemoryLocation::UnknownSize,
1221 V2AAInfo, nullptr, UnderlyingV2);
1223 // If V2 may alias GEP base pointer, conservatively returns MayAlias.
1224 // If V2 is known not to alias GEP base pointer, then the two values
1225 // cannot alias per GEP semantics: "Any memory access must be done through
1226 // a pointer value associated with an address range of the memory access,
1227 // otherwise the behavior is undefined.".
1230 // If the max search depth is reached the result is undefined
1231 if (GEP1MaxLookupReached)
1235 // In the two GEP Case, if there is no difference in the offsets of the
1236 // computed pointers, the resultant pointers are a must alias. This
1237 // happens when we have two lexically identical GEP's (for example).
1239 // In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
1240 // must aliases the GEP, the end result is a must alias also.
1241 if (GEP1BaseOffset == 0 && DecompGEP1.VarIndices.empty())
1244 // If there is a constant difference between the pointers, but the difference
1245 // is less than the size of the associated memory object, then we know
1246 // that the objects are partially overlapping. If the difference is
1247 // greater, we know they do not overlap.
1248 if (GEP1BaseOffset != 0 && DecompGEP1.VarIndices.empty()) {
1249 if (GEP1BaseOffset >= 0) {
1250 if (V2Size != MemoryLocation::UnknownSize) {
1251 if ((uint64_t)GEP1BaseOffset < V2Size)
1252 return PartialAlias;
1256 // We have the situation where:
1259 // ---------------->|
1260 // |-->V1Size |-------> V2Size
1262 // We need to know that V2Size is not unknown, otherwise we might have
1263 // stripped a gep with negative index ('gep <ptr>, -1, ...).
1264 if (V1Size != MemoryLocation::UnknownSize &&
1265 V2Size != MemoryLocation::UnknownSize) {
1266 if (-(uint64_t)GEP1BaseOffset < V1Size)
1267 return PartialAlias;
1273 if (!DecompGEP1.VarIndices.empty()) {
1274 uint64_t Modulo = 0;
1275 bool AllPositive = true;
1276 for (unsigned i = 0, e = DecompGEP1.VarIndices.size(); i != e; ++i) {
1278 // Try to distinguish something like &A[i][1] against &A[42][0].
1279 // Grab the least significant bit set in any of the scales. We
1280 // don't need std::abs here (even if the scale's negative) as we'll
1281 // be ^'ing Modulo with itself later.
1282 Modulo |= (uint64_t)DecompGEP1.VarIndices[i].Scale;
1285 // If the Value could change between cycles, then any reasoning about
1286 // the Value this cycle may not hold in the next cycle. We'll just
1287 // give up if we can't determine conditions that hold for every cycle:
1288 const Value *V = DecompGEP1.VarIndices[i].V;
1290 KnownBits Known = computeKnownBits(V, DL, 0, &AC, nullptr, DT);
1291 bool SignKnownZero = Known.isNonNegative();
1292 bool SignKnownOne = Known.isNegative();
1294 // Zero-extension widens the variable, and so forces the sign
1296 bool IsZExt = DecompGEP1.VarIndices[i].ZExtBits > 0 || isa<ZExtInst>(V);
1297 SignKnownZero |= IsZExt;
1298 SignKnownOne &= !IsZExt;
1300 // If the variable begins with a zero then we know it's
1301 // positive, regardless of whether the value is signed or
1303 int64_t Scale = DecompGEP1.VarIndices[i].Scale;
1305 (SignKnownZero && Scale >= 0) || (SignKnownOne && Scale < 0);
1309 Modulo = Modulo ^ (Modulo & (Modulo - 1));
1311 // We can compute the difference between the two addresses
1312 // mod Modulo. Check whether that difference guarantees that the
1313 // two locations do not alias.
1314 uint64_t ModOffset = (uint64_t)GEP1BaseOffset & (Modulo - 1);
1315 if (V1Size != MemoryLocation::UnknownSize &&
1316 V2Size != MemoryLocation::UnknownSize && ModOffset >= V2Size &&
1317 V1Size <= Modulo - ModOffset)
1320 // If we know all the variables are positive, then GEP1 >= GEP1BasePtr.
1321 // If GEP1BasePtr > V2 (GEP1BaseOffset > 0) then we know the pointers
1322 // don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
1323 if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t)GEP1BaseOffset)
1326 if (constantOffsetHeuristic(DecompGEP1.VarIndices, V1Size, V2Size,
1327 GEP1BaseOffset, &AC, DT))
1331 // Statically, we can see that the base objects are the same, but the
1332 // pointers have dynamic offsets which we can't resolve. And none of our
1333 // little tricks above worked.
1335 // TODO: Returning PartialAlias instead of MayAlias is a mild hack; the
1336 // practical effect of this is protecting TBAA in the case of dynamic
1337 // indices into arrays of unions or malloc'd memory.
1338 return PartialAlias;
1341 static AliasResult MergeAliasResults(AliasResult A, AliasResult B) {
1342 // If the results agree, take it.
1345 // A mix of PartialAlias and MustAlias is PartialAlias.
1346 if ((A == PartialAlias && B == MustAlias) ||
1347 (B == PartialAlias && A == MustAlias))
1348 return PartialAlias;
1349 // Otherwise, we don't know anything.
1353 /// Provides a bunch of ad-hoc rules to disambiguate a Select instruction
1354 /// against another.
1355 AliasResult BasicAAResult::aliasSelect(const SelectInst *SI, uint64_t SISize,
1356 const AAMDNodes &SIAAInfo,
1357 const Value *V2, uint64_t V2Size,
1358 const AAMDNodes &V2AAInfo,
1359 const Value *UnderV2) {
1360 // If the values are Selects with the same condition, we can do a more precise
1361 // check: just check for aliases between the values on corresponding arms.
1362 if (const SelectInst *SI2 = dyn_cast<SelectInst>(V2))
1363 if (SI->getCondition() == SI2->getCondition()) {
1364 AliasResult Alias = aliasCheck(SI->getTrueValue(), SISize, SIAAInfo,
1365 SI2->getTrueValue(), V2Size, V2AAInfo);
1366 if (Alias == MayAlias)
1368 AliasResult ThisAlias =
1369 aliasCheck(SI->getFalseValue(), SISize, SIAAInfo,
1370 SI2->getFalseValue(), V2Size, V2AAInfo);
1371 return MergeAliasResults(ThisAlias, Alias);
1374 // If both arms of the Select node NoAlias or MustAlias V2, then returns
1375 // NoAlias / MustAlias. Otherwise, returns MayAlias.
1377 aliasCheck(V2, V2Size, V2AAInfo, SI->getTrueValue(),
1378 SISize, SIAAInfo, UnderV2);
1379 if (Alias == MayAlias)
1382 AliasResult ThisAlias =
1383 aliasCheck(V2, V2Size, V2AAInfo, SI->getFalseValue(), SISize, SIAAInfo,
1385 return MergeAliasResults(ThisAlias, Alias);
1388 /// Provide a bunch of ad-hoc rules to disambiguate a PHI instruction against
1390 AliasResult BasicAAResult::aliasPHI(const PHINode *PN, uint64_t PNSize,
1391 const AAMDNodes &PNAAInfo, const Value *V2,
1392 uint64_t V2Size, const AAMDNodes &V2AAInfo,
1393 const Value *UnderV2) {
1394 // Track phi nodes we have visited. We use this information when we determine
1395 // value equivalence.
1396 VisitedPhiBBs.insert(PN->getParent());
1398 // If the values are PHIs in the same block, we can do a more precise
1399 // as well as efficient check: just check for aliases between the values
1400 // on corresponding edges.
1401 if (const PHINode *PN2 = dyn_cast<PHINode>(V2))
1402 if (PN2->getParent() == PN->getParent()) {
1403 LocPair Locs(MemoryLocation(PN, PNSize, PNAAInfo),
1404 MemoryLocation(V2, V2Size, V2AAInfo));
1406 std::swap(Locs.first, Locs.second);
1407 // Analyse the PHIs' inputs under the assumption that the PHIs are
1409 // If the PHIs are May/MustAlias there must be (recursively) an input
1410 // operand from outside the PHIs' cycle that is MayAlias/MustAlias or
1411 // there must be an operation on the PHIs within the PHIs' value cycle
1412 // that causes a MayAlias.
1413 // Pretend the phis do not alias.
1414 AliasResult Alias = NoAlias;
1415 assert(AliasCache.count(Locs) &&
1416 "There must exist an entry for the phi node");
1417 AliasResult OrigAliasResult = AliasCache[Locs];
1418 AliasCache[Locs] = NoAlias;
1420 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1421 AliasResult ThisAlias =
1422 aliasCheck(PN->getIncomingValue(i), PNSize, PNAAInfo,
1423 PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
1425 Alias = MergeAliasResults(ThisAlias, Alias);
1426 if (Alias == MayAlias)
1430 // Reset if speculation failed.
1431 if (Alias != NoAlias)
1432 AliasCache[Locs] = OrigAliasResult;
1437 SmallPtrSet<Value *, 4> UniqueSrc;
1438 SmallVector<Value *, 4> V1Srcs;
1439 bool isRecursive = false;
1440 for (Value *PV1 : PN->incoming_values()) {
1441 if (isa<PHINode>(PV1))
1442 // If any of the source itself is a PHI, return MayAlias conservatively
1443 // to avoid compile time explosion. The worst possible case is if both
1444 // sides are PHI nodes. In which case, this is O(m x n) time where 'm'
1445 // and 'n' are the number of PHI sources.
1448 if (EnableRecPhiAnalysis)
1449 if (GEPOperator *PV1GEP = dyn_cast<GEPOperator>(PV1)) {
1450 // Check whether the incoming value is a GEP that advances the pointer
1451 // result of this PHI node (e.g. in a loop). If this is the case, we
1452 // would recurse and always get a MayAlias. Handle this case specially
1454 if (PV1GEP->getPointerOperand() == PN && PV1GEP->getNumIndices() == 1 &&
1455 isa<ConstantInt>(PV1GEP->idx_begin())) {
1461 if (UniqueSrc.insert(PV1).second)
1462 V1Srcs.push_back(PV1);
1465 // If this PHI node is recursive, set the size of the accessed memory to
1466 // unknown to represent all the possible values the GEP could advance the
1469 PNSize = MemoryLocation::UnknownSize;
1472 aliasCheck(V2, V2Size, V2AAInfo, V1Srcs[0],
1473 PNSize, PNAAInfo, UnderV2);
1475 // Early exit if the check of the first PHI source against V2 is MayAlias.
1476 // Other results are not possible.
1477 if (Alias == MayAlias)
1480 // If all sources of the PHI node NoAlias or MustAlias V2, then returns
1481 // NoAlias / MustAlias. Otherwise, returns MayAlias.
1482 for (unsigned i = 1, e = V1Srcs.size(); i != e; ++i) {
1483 Value *V = V1Srcs[i];
1485 AliasResult ThisAlias =
1486 aliasCheck(V2, V2Size, V2AAInfo, V, PNSize, PNAAInfo, UnderV2);
1487 Alias = MergeAliasResults(ThisAlias, Alias);
1488 if (Alias == MayAlias)
1495 /// Provides a bunch of ad-hoc rules to disambiguate in common cases, such as
1496 /// array references.
1497 AliasResult BasicAAResult::aliasCheck(const Value *V1, uint64_t V1Size,
1498 AAMDNodes V1AAInfo, const Value *V2,
1499 uint64_t V2Size, AAMDNodes V2AAInfo,
1500 const Value *O1, const Value *O2) {
1501 // If either of the memory references is empty, it doesn't matter what the
1502 // pointer values are.
1503 if (V1Size == 0 || V2Size == 0)
1506 // Strip off any casts if they exist.
1507 V1 = V1->stripPointerCastsAndBarriers();
1508 V2 = V2->stripPointerCastsAndBarriers();
1510 // If V1 or V2 is undef, the result is NoAlias because we can always pick a
1511 // value for undef that aliases nothing in the program.
1512 if (isa<UndefValue>(V1) || isa<UndefValue>(V2))
1515 // Are we checking for alias of the same value?
1516 // Because we look 'through' phi nodes, we could look at "Value" pointers from
1517 // different iterations. We must therefore make sure that this is not the
1518 // case. The function isValueEqualInPotentialCycles ensures that this cannot
1519 // happen by looking at the visited phi nodes and making sure they cannot
1521 if (isValueEqualInPotentialCycles(V1, V2))
1524 if (!V1->getType()->isPointerTy() || !V2->getType()->isPointerTy())
1525 return NoAlias; // Scalars cannot alias each other
1527 // Figure out what objects these things are pointing to if we can.
1529 O1 = GetUnderlyingObject(V1, DL, MaxLookupSearchDepth);
1532 O2 = GetUnderlyingObject(V2, DL, MaxLookupSearchDepth);
1534 // Null values in the default address space don't point to any object, so they
1535 // don't alias any other pointer.
1536 if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O1))
1537 if (CPN->getType()->getAddressSpace() == 0)
1539 if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O2))
1540 if (CPN->getType()->getAddressSpace() == 0)
1544 // If V1/V2 point to two different objects, we know that we have no alias.
1545 if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
1548 // Constant pointers can't alias with non-const isIdentifiedObject objects.
1549 if ((isa<Constant>(O1) && isIdentifiedObject(O2) && !isa<Constant>(O2)) ||
1550 (isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
1553 // Function arguments can't alias with things that are known to be
1554 // unambigously identified at the function level.
1555 if ((isa<Argument>(O1) && isIdentifiedFunctionLocal(O2)) ||
1556 (isa<Argument>(O2) && isIdentifiedFunctionLocal(O1)))
1559 // Most objects can't alias null.
1560 if ((isa<ConstantPointerNull>(O2) && isKnownNonNull(O1)) ||
1561 (isa<ConstantPointerNull>(O1) && isKnownNonNull(O2)))
1564 // If one pointer is the result of a call/invoke or load and the other is a
1565 // non-escaping local object within the same function, then we know the
1566 // object couldn't escape to a point where the call could return it.
1568 // Note that if the pointers are in different functions, there are a
1569 // variety of complications. A call with a nocapture argument may still
1570 // temporary store the nocapture argument's value in a temporary memory
1571 // location if that memory location doesn't escape. Or it may pass a
1572 // nocapture value to other functions as long as they don't capture it.
1573 if (isEscapeSource(O1) && isNonEscapingLocalObject(O2))
1575 if (isEscapeSource(O2) && isNonEscapingLocalObject(O1))
1579 // If the size of one access is larger than the entire object on the other
1580 // side, then we know such behavior is undefined and can assume no alias.
1581 if ((V1Size != MemoryLocation::UnknownSize &&
1582 isObjectSmallerThan(O2, V1Size, DL, TLI)) ||
1583 (V2Size != MemoryLocation::UnknownSize &&
1584 isObjectSmallerThan(O1, V2Size, DL, TLI)))
1587 // Check the cache before climbing up use-def chains. This also terminates
1588 // otherwise infinitely recursive queries.
1589 LocPair Locs(MemoryLocation(V1, V1Size, V1AAInfo),
1590 MemoryLocation(V2, V2Size, V2AAInfo));
1592 std::swap(Locs.first, Locs.second);
1593 std::pair<AliasCacheTy::iterator, bool> Pair =
1594 AliasCache.insert(std::make_pair(Locs, MayAlias));
1596 return Pair.first->second;
1598 // FIXME: This isn't aggressively handling alias(GEP, PHI) for example: if the
1599 // GEP can't simplify, we don't even look at the PHI cases.
1600 if (!isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
1602 std::swap(V1Size, V2Size);
1604 std::swap(V1AAInfo, V2AAInfo);
1606 if (const GEPOperator *GV1 = dyn_cast<GEPOperator>(V1)) {
1607 AliasResult Result =
1608 aliasGEP(GV1, V1Size, V1AAInfo, V2, V2Size, V2AAInfo, O1, O2);
1609 if (Result != MayAlias)
1610 return AliasCache[Locs] = Result;
1613 if (isa<PHINode>(V2) && !isa<PHINode>(V1)) {
1616 std::swap(V1Size, V2Size);
1617 std::swap(V1AAInfo, V2AAInfo);
1619 if (const PHINode *PN = dyn_cast<PHINode>(V1)) {
1620 AliasResult Result = aliasPHI(PN, V1Size, V1AAInfo,
1621 V2, V2Size, V2AAInfo, O2);
1622 if (Result != MayAlias)
1623 return AliasCache[Locs] = Result;
1626 if (isa<SelectInst>(V2) && !isa<SelectInst>(V1)) {
1629 std::swap(V1Size, V2Size);
1630 std::swap(V1AAInfo, V2AAInfo);
1632 if (const SelectInst *S1 = dyn_cast<SelectInst>(V1)) {
1633 AliasResult Result =
1634 aliasSelect(S1, V1Size, V1AAInfo, V2, V2Size, V2AAInfo, O2);
1635 if (Result != MayAlias)
1636 return AliasCache[Locs] = Result;
1639 // If both pointers are pointing into the same object and one of them
1640 // accesses the entire object, then the accesses must overlap in some way.
1642 if ((V1Size != MemoryLocation::UnknownSize &&
1643 isObjectSize(O1, V1Size, DL, TLI)) ||
1644 (V2Size != MemoryLocation::UnknownSize &&
1645 isObjectSize(O2, V2Size, DL, TLI)))
1646 return AliasCache[Locs] = PartialAlias;
1648 // Recurse back into the best AA results we have, potentially with refined
1649 // memory locations. We have already ensured that BasicAA has a MayAlias
1650 // cache result for these, so any recursion back into BasicAA won't loop.
1651 AliasResult Result = getBestAAResults().alias(Locs.first, Locs.second);
1652 return AliasCache[Locs] = Result;
1655 /// Check whether two Values can be considered equivalent.
1657 /// In addition to pointer equivalence of \p V1 and \p V2 this checks whether
1658 /// they can not be part of a cycle in the value graph by looking at all
1659 /// visited phi nodes an making sure that the phis cannot reach the value. We
1660 /// have to do this because we are looking through phi nodes (That is we say
1661 /// noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
1662 bool BasicAAResult::isValueEqualInPotentialCycles(const Value *V,
1667 const Instruction *Inst = dyn_cast<Instruction>(V);
1671 if (VisitedPhiBBs.empty())
1674 if (VisitedPhiBBs.size() > MaxNumPhiBBsValueReachabilityCheck)
1677 // Make sure that the visited phis cannot reach the Value. This ensures that
1678 // the Values cannot come from different iterations of a potential cycle the
1679 // phi nodes could be involved in.
1680 for (auto *P : VisitedPhiBBs)
1681 if (isPotentiallyReachable(&P->front(), Inst, DT, LI))
1687 /// Computes the symbolic difference between two de-composed GEPs.
1689 /// Dest and Src are the variable indices from two decomposed GetElementPtr
1690 /// instructions GEP1 and GEP2 which have common base pointers.
1691 void BasicAAResult::GetIndexDifference(
1692 SmallVectorImpl<VariableGEPIndex> &Dest,
1693 const SmallVectorImpl<VariableGEPIndex> &Src) {
1697 for (unsigned i = 0, e = Src.size(); i != e; ++i) {
1698 const Value *V = Src[i].V;
1699 unsigned ZExtBits = Src[i].ZExtBits, SExtBits = Src[i].SExtBits;
1700 int64_t Scale = Src[i].Scale;
1702 // Find V in Dest. This is N^2, but pointer indices almost never have more
1703 // than a few variable indexes.
1704 for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
1705 if (!isValueEqualInPotentialCycles(Dest[j].V, V) ||
1706 Dest[j].ZExtBits != ZExtBits || Dest[j].SExtBits != SExtBits)
1709 // If we found it, subtract off Scale V's from the entry in Dest. If it
1710 // goes to zero, remove the entry.
1711 if (Dest[j].Scale != Scale)
1712 Dest[j].Scale -= Scale;
1714 Dest.erase(Dest.begin() + j);
1719 // If we didn't consume this entry, add it to the end of the Dest list.
1721 VariableGEPIndex Entry = {V, ZExtBits, SExtBits, -Scale};
1722 Dest.push_back(Entry);
1727 bool BasicAAResult::constantOffsetHeuristic(
1728 const SmallVectorImpl<VariableGEPIndex> &VarIndices, uint64_t V1Size,
1729 uint64_t V2Size, int64_t BaseOffset, AssumptionCache *AC,
1730 DominatorTree *DT) {
1731 if (VarIndices.size() != 2 || V1Size == MemoryLocation::UnknownSize ||
1732 V2Size == MemoryLocation::UnknownSize)
1735 const VariableGEPIndex &Var0 = VarIndices[0], &Var1 = VarIndices[1];
1737 if (Var0.ZExtBits != Var1.ZExtBits || Var0.SExtBits != Var1.SExtBits ||
1738 Var0.Scale != -Var1.Scale)
1741 unsigned Width = Var1.V->getType()->getIntegerBitWidth();
1743 // We'll strip off the Extensions of Var0 and Var1 and do another round
1744 // of GetLinearExpression decomposition. In the example above, if Var0
1745 // is zext(%x + 1) we should get V1 == %x and V1Offset == 1.
1747 APInt V0Scale(Width, 0), V0Offset(Width, 0), V1Scale(Width, 0),
1749 bool NSW = true, NUW = true;
1750 unsigned V0ZExtBits = 0, V0SExtBits = 0, V1ZExtBits = 0, V1SExtBits = 0;
1751 const Value *V0 = GetLinearExpression(Var0.V, V0Scale, V0Offset, V0ZExtBits,
1752 V0SExtBits, DL, 0, AC, DT, NSW, NUW);
1755 const Value *V1 = GetLinearExpression(Var1.V, V1Scale, V1Offset, V1ZExtBits,
1756 V1SExtBits, DL, 0, AC, DT, NSW, NUW);
1758 if (V0Scale != V1Scale || V0ZExtBits != V1ZExtBits ||
1759 V0SExtBits != V1SExtBits || !isValueEqualInPotentialCycles(V0, V1))
1762 // We have a hit - Var0 and Var1 only differ by a constant offset!
1764 // If we've been sext'ed then zext'd the maximum difference between Var0 and
1765 // Var1 is possible to calculate, but we're just interested in the absolute
1766 // minimum difference between the two. The minimum distance may occur due to
1767 // wrapping; consider "add i3 %i, 5": if %i == 7 then 7 + 5 mod 8 == 4, and so
1768 // the minimum distance between %i and %i + 5 is 3.
1769 APInt MinDiff = V0Offset - V1Offset, Wrapped = -MinDiff;
1770 MinDiff = APIntOps::umin(MinDiff, Wrapped);
1771 uint64_t MinDiffBytes = MinDiff.getZExtValue() * std::abs(Var0.Scale);
1773 // We can't definitely say whether GEP1 is before or after V2 due to wrapping
1774 // arithmetic (i.e. for some values of GEP1 and V2 GEP1 < V2, and for other
1775 // values GEP1 > V2). We'll therefore only declare NoAlias if both V1Size and
1776 // V2Size can fit in the MinDiffBytes gap.
1777 return V1Size + std::abs(BaseOffset) <= MinDiffBytes &&
1778 V2Size + std::abs(BaseOffset) <= MinDiffBytes;
1781 //===----------------------------------------------------------------------===//
1782 // BasicAliasAnalysis Pass
1783 //===----------------------------------------------------------------------===//
1785 AnalysisKey BasicAA::Key;
1787 BasicAAResult BasicAA::run(Function &F, FunctionAnalysisManager &AM) {
1788 return BasicAAResult(F.getParent()->getDataLayout(),
1789 AM.getResult<TargetLibraryAnalysis>(F),
1790 AM.getResult<AssumptionAnalysis>(F),
1791 &AM.getResult<DominatorTreeAnalysis>(F),
1792 AM.getCachedResult<LoopAnalysis>(F));
1795 BasicAAWrapperPass::BasicAAWrapperPass() : FunctionPass(ID) {
1796 initializeBasicAAWrapperPassPass(*PassRegistry::getPassRegistry());
1799 char BasicAAWrapperPass::ID = 0;
1800 void BasicAAWrapperPass::anchor() {}
1802 INITIALIZE_PASS_BEGIN(BasicAAWrapperPass, "basicaa",
1803 "Basic Alias Analysis (stateless AA impl)", true, true)
1804 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
1805 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1806 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
1807 INITIALIZE_PASS_END(BasicAAWrapperPass, "basicaa",
1808 "Basic Alias Analysis (stateless AA impl)", true, true)
1810 FunctionPass *llvm::createBasicAAWrapperPass() {
1811 return new BasicAAWrapperPass();
1814 bool BasicAAWrapperPass::runOnFunction(Function &F) {
1815 auto &ACT = getAnalysis<AssumptionCacheTracker>();
1816 auto &TLIWP = getAnalysis<TargetLibraryInfoWrapperPass>();
1817 auto &DTWP = getAnalysis<DominatorTreeWrapperPass>();
1818 auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
1820 Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), TLIWP.getTLI(),
1821 ACT.getAssumptionCache(F), &DTWP.getDomTree(),
1822 LIWP ? &LIWP->getLoopInfo() : nullptr));
1827 void BasicAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
1828 AU.setPreservesAll();
1829 AU.addRequired<AssumptionCacheTracker>();
1830 AU.addRequired<DominatorTreeWrapperPass>();
1831 AU.addRequired<TargetLibraryInfoWrapperPass>();
1834 BasicAAResult llvm::createLegacyPMBasicAAResult(Pass &P, Function &F) {
1835 return BasicAAResult(
1836 F.getParent()->getDataLayout(),
1837 P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
1838 P.getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F));