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/CFG.h"
21 #include "llvm/Analysis/CaptureTracking.h"
22 #include "llvm/Analysis/InstructionSimplify.h"
23 #include "llvm/Analysis/LoopInfo.h"
24 #include "llvm/Analysis/MemoryBuiltins.h"
25 #include "llvm/Analysis/ValueTracking.h"
26 #include "llvm/Analysis/AssumptionCache.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"
41 #define DEBUG_TYPE "basicaa"
45 /// Enable analysis of recursive PHI nodes.
46 static cl::opt<bool> EnableRecPhiAnalysis("basicaa-recphi", cl::Hidden,
48 /// SearchLimitReached / SearchTimes shows how often the limit of
49 /// to decompose GEPs is reached. It will affect the precision
50 /// of basic alias analysis.
51 STATISTIC(SearchLimitReached, "Number of times the limit to "
52 "decompose GEPs is reached");
53 STATISTIC(SearchTimes, "Number of times a GEP is decomposed");
55 /// Cutoff after which to stop analysing a set of phi nodes potentially involved
56 /// in a cycle. Because we are analysing 'through' phi nodes, we need to be
57 /// careful with value equivalence. We use reachability to make sure a value
58 /// cannot be involved in a cycle.
59 const unsigned MaxNumPhiBBsValueReachabilityCheck = 20;
61 // The max limit of the search depth in DecomposeGEPExpression() and
62 // GetUnderlyingObject(), both functions need to use the same search
63 // depth otherwise the algorithm in aliasGEP will assert.
64 static const unsigned MaxLookupSearchDepth = 6;
66 bool BasicAAResult::invalidate(Function &F, const PreservedAnalyses &PA,
67 FunctionAnalysisManager::Invalidator &Inv) {
68 // We don't care if this analysis itself is preserved, it has no state. But
69 // we need to check that the analyses it depends on have been. Note that we
70 // may be created without handles to some analyses and in that case don't
72 if (Inv.invalidate<AssumptionAnalysis>(F, PA) ||
73 (DT && Inv.invalidate<DominatorTreeAnalysis>(F, PA)) ||
74 (LI && Inv.invalidate<LoopAnalysis>(F, PA)))
77 // Otherwise this analysis result remains valid.
81 //===----------------------------------------------------------------------===//
83 //===----------------------------------------------------------------------===//
85 /// Returns true if the pointer is to a function-local object that never
86 /// escapes from the function.
87 static bool isNonEscapingLocalObject(const Value *V) {
88 // If this is a local allocation, check to see if it escapes.
89 if (isa<AllocaInst>(V) || isNoAliasCall(V))
90 // Set StoreCaptures to True so that we can assume in our callers that the
91 // pointer is not the result of a load instruction. Currently
92 // PointerMayBeCaptured doesn't have any special analysis for the
93 // StoreCaptures=false case; if it did, our callers could be refined to be
95 return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
97 // If this is an argument that corresponds to a byval or noalias argument,
98 // then it has not escaped before entering the function. Check if it escapes
99 // inside the function.
100 if (const Argument *A = dyn_cast<Argument>(V))
101 if (A->hasByValAttr() || A->hasNoAliasAttr())
102 // Note even if the argument is marked nocapture, we still need to check
103 // for copies made inside the function. The nocapture attribute only
104 // specifies that there are no copies made that outlive the function.
105 return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
110 /// Returns true if the pointer is one which would have been considered an
111 /// escape by isNonEscapingLocalObject.
112 static bool isEscapeSource(const Value *V) {
113 if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
116 // The load case works because isNonEscapingLocalObject considers all
117 // stores to be escapes (it passes true for the StoreCaptures argument
118 // to PointerMayBeCaptured).
119 if (isa<LoadInst>(V))
125 /// Returns the size of the object specified by V or UnknownSize if unknown.
126 static uint64_t getObjectSize(const Value *V, const DataLayout &DL,
127 const TargetLibraryInfo &TLI,
128 bool RoundToAlign = false) {
131 Opts.RoundToAlign = RoundToAlign;
132 if (getObjectSize(V, Size, DL, &TLI, Opts))
134 return MemoryLocation::UnknownSize;
137 /// Returns true if we can prove that the object specified by V is smaller than
139 static bool isObjectSmallerThan(const Value *V, uint64_t Size,
140 const DataLayout &DL,
141 const TargetLibraryInfo &TLI) {
142 // Note that the meanings of the "object" are slightly different in the
143 // following contexts:
144 // c1: llvm::getObjectSize()
145 // c2: llvm.objectsize() intrinsic
146 // c3: isObjectSmallerThan()
147 // c1 and c2 share the same meaning; however, the meaning of "object" in c3
148 // refers to the "entire object".
150 // Consider this example:
151 // char *p = (char*)malloc(100)
154 // In the context of c1 and c2, the "object" pointed by q refers to the
155 // stretch of memory of q[0:19]. So, getObjectSize(q) should return 20.
157 // However, in the context of c3, the "object" refers to the chunk of memory
158 // being allocated. So, the "object" has 100 bytes, and q points to the middle
159 // the "object". In case q is passed to isObjectSmallerThan() as the 1st
160 // parameter, before the llvm::getObjectSize() is called to get the size of
161 // entire object, we should:
162 // - either rewind the pointer q to the base-address of the object in
163 // question (in this case rewind to p), or
164 // - just give up. It is up to caller to make sure the pointer is pointing
165 // to the base address the object.
167 // We go for 2nd option for simplicity.
168 if (!isIdentifiedObject(V))
171 // This function needs to use the aligned object size because we allow
172 // reads a bit past the end given sufficient alignment.
173 uint64_t ObjectSize = getObjectSize(V, DL, TLI, /*RoundToAlign*/ true);
175 return ObjectSize != MemoryLocation::UnknownSize && ObjectSize < Size;
178 /// Returns true if we can prove that the object specified by V has size Size.
179 static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
180 const TargetLibraryInfo &TLI) {
181 uint64_t ObjectSize = getObjectSize(V, DL, TLI);
182 return ObjectSize != MemoryLocation::UnknownSize && ObjectSize == Size;
185 //===----------------------------------------------------------------------===//
186 // GetElementPtr Instruction Decomposition and Analysis
187 //===----------------------------------------------------------------------===//
189 /// Analyzes the specified value as a linear expression: "A*V + B", where A and
190 /// B are constant integers.
192 /// Returns the scale and offset values as APInts and return V as a Value*, and
193 /// return whether we looked through any sign or zero extends. The incoming
194 /// Value is known to have IntegerType, and it may already be sign or zero
197 /// Note that this looks through extends, so the high bits may not be
198 /// represented in the result.
199 /*static*/ const Value *BasicAAResult::GetLinearExpression(
200 const Value *V, APInt &Scale, APInt &Offset, unsigned &ZExtBits,
201 unsigned &SExtBits, const DataLayout &DL, unsigned Depth,
202 AssumptionCache *AC, DominatorTree *DT, bool &NSW, bool &NUW) {
203 assert(V->getType()->isIntegerTy() && "Not an integer value");
205 // Limit our recursion depth.
212 if (const ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
213 // If it's a constant, just convert it to an offset and remove the variable.
214 // If we've been called recursively, the Offset bit width will be greater
215 // than the constant's (the Offset's always as wide as the outermost call),
216 // so we'll zext here and process any extension in the isa<SExtInst> &
217 // isa<ZExtInst> cases below.
218 Offset += Const->getValue().zextOrSelf(Offset.getBitWidth());
219 assert(Scale == 0 && "Constant values don't have a scale");
223 if (const BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
224 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
226 // If we've been called recursively, then Offset and Scale will be wider
227 // than the BOp operands. We'll always zext it here as we'll process sign
228 // extensions below (see the isa<SExtInst> / isa<ZExtInst> cases).
229 APInt RHS = RHSC->getValue().zextOrSelf(Offset.getBitWidth());
231 switch (BOp->getOpcode()) {
233 // We don't understand this instruction, so we can't decompose it any
238 case Instruction::Or:
239 // X|C == X+C if all the bits in C are unset in X. Otherwise we can't
241 if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), DL, 0, AC,
248 case Instruction::Add:
249 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
250 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
253 case Instruction::Sub:
254 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
255 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
258 case Instruction::Mul:
259 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
260 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
264 case Instruction::Shl:
265 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
266 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
267 Offset <<= RHS.getLimitedValue();
268 Scale <<= RHS.getLimitedValue();
269 // the semantics of nsw and nuw for left shifts don't match those of
270 // multiplications, so we won't propagate them.
275 if (isa<OverflowingBinaryOperator>(BOp)) {
276 NUW &= BOp->hasNoUnsignedWrap();
277 NSW &= BOp->hasNoSignedWrap();
283 // Since GEP indices are sign extended anyway, we don't care about the high
284 // bits of a sign or zero extended value - just scales and offsets. The
285 // extensions have to be consistent though.
286 if (isa<SExtInst>(V) || isa<ZExtInst>(V)) {
287 Value *CastOp = cast<CastInst>(V)->getOperand(0);
288 unsigned NewWidth = V->getType()->getPrimitiveSizeInBits();
289 unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
290 unsigned OldZExtBits = ZExtBits, OldSExtBits = SExtBits;
291 const Value *Result =
292 GetLinearExpression(CastOp, Scale, Offset, ZExtBits, SExtBits, DL,
293 Depth + 1, AC, DT, NSW, NUW);
295 // zext(zext(%x)) == zext(%x), and similarly for sext; we'll handle this
296 // by just incrementing the number of bits we've extended by.
297 unsigned ExtendedBy = NewWidth - SmallWidth;
299 if (isa<SExtInst>(V) && ZExtBits == 0) {
300 // sext(sext(%x, a), b) == sext(%x, a + b)
303 // We haven't sign-wrapped, so it's valid to decompose sext(%x + c)
304 // into sext(%x) + sext(c). We'll sext the Offset ourselves:
305 unsigned OldWidth = Offset.getBitWidth();
306 Offset = Offset.trunc(SmallWidth).sext(NewWidth).zextOrSelf(OldWidth);
308 // We may have signed-wrapped, so don't decompose sext(%x + c) into
309 // sext(%x) + sext(c)
313 ZExtBits = OldZExtBits;
314 SExtBits = OldSExtBits;
316 SExtBits += ExtendedBy;
318 // sext(zext(%x, a), b) = zext(zext(%x, a), b) = zext(%x, a + b)
321 // We may have unsigned-wrapped, so don't decompose zext(%x + c) into
322 // zext(%x) + zext(c)
326 ZExtBits = OldZExtBits;
327 SExtBits = OldSExtBits;
329 ZExtBits += ExtendedBy;
340 /// To ensure a pointer offset fits in an integer of size PointerSize
341 /// (in bits) when that size is smaller than 64. This is an issue in
342 /// particular for 32b programs with negative indices that rely on two's
343 /// complement wrap-arounds for precise alias information.
344 static int64_t adjustToPointerSize(int64_t Offset, unsigned PointerSize) {
345 assert(PointerSize <= 64 && "Invalid PointerSize!");
346 unsigned ShiftBits = 64 - PointerSize;
347 return (int64_t)((uint64_t)Offset << ShiftBits) >> ShiftBits;
350 /// If V is a symbolic pointer expression, decompose it into a base pointer
351 /// with a constant offset and a number of scaled symbolic offsets.
353 /// The scaled symbolic offsets (represented by pairs of a Value* and a scale
354 /// in the VarIndices vector) are Value*'s that are known to be scaled by the
355 /// specified amount, but which may have other unrepresented high bits. As
356 /// such, the gep cannot necessarily be reconstructed from its decomposed form.
358 /// When DataLayout is around, this function is capable of analyzing everything
359 /// that GetUnderlyingObject can look through. To be able to do that
360 /// GetUnderlyingObject and DecomposeGEPExpression must use the same search
361 /// depth (MaxLookupSearchDepth). When DataLayout not is around, it just looks
362 /// through pointer casts.
363 bool BasicAAResult::DecomposeGEPExpression(const Value *V,
364 DecomposedGEP &Decomposed, const DataLayout &DL, AssumptionCache *AC,
366 // Limit recursion depth to limit compile time in crazy cases.
367 unsigned MaxLookup = MaxLookupSearchDepth;
370 Decomposed.StructOffset = 0;
371 Decomposed.OtherOffset = 0;
372 Decomposed.VarIndices.clear();
374 // See if this is a bitcast or GEP.
375 const Operator *Op = dyn_cast<Operator>(V);
377 // The only non-operator case we can handle are GlobalAliases.
378 if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
379 if (!GA->isInterposable()) {
380 V = GA->getAliasee();
388 if (Op->getOpcode() == Instruction::BitCast ||
389 Op->getOpcode() == Instruction::AddrSpaceCast) {
390 V = Op->getOperand(0);
394 const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
396 if (auto CS = ImmutableCallSite(V))
397 if (const Value *RV = CS.getReturnedArgOperand()) {
402 // If it's not a GEP, hand it off to SimplifyInstruction to see if it
403 // can come up with something. This matches what GetUnderlyingObject does.
404 if (const Instruction *I = dyn_cast<Instruction>(V))
405 // TODO: Get a DominatorTree and AssumptionCache and use them here
406 // (these are both now available in this function, but this should be
407 // updated when GetUnderlyingObject is updated). TLI should be
409 if (const Value *Simplified =
410 SimplifyInstruction(const_cast<Instruction *>(I), DL)) {
419 // Don't attempt to analyze GEPs over unsized objects.
420 if (!GEPOp->getSourceElementType()->isSized()) {
425 unsigned AS = GEPOp->getPointerAddressSpace();
426 // Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
427 gep_type_iterator GTI = gep_type_begin(GEPOp);
428 unsigned PointerSize = DL.getPointerSizeInBits(AS);
429 // Assume all GEP operands are constants until proven otherwise.
430 bool GepHasConstantOffset = true;
431 for (User::const_op_iterator I = GEPOp->op_begin() + 1, E = GEPOp->op_end();
432 I != E; ++I, ++GTI) {
433 const Value *Index = *I;
434 // Compute the (potentially symbolic) offset in bytes for this index.
435 if (StructType *STy = GTI.getStructTypeOrNull()) {
436 // For a struct, add the member offset.
437 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
441 Decomposed.StructOffset +=
442 DL.getStructLayout(STy)->getElementOffset(FieldNo);
446 // For an array/pointer, add the element offset, explicitly scaled.
447 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
450 Decomposed.OtherOffset +=
451 DL.getTypeAllocSize(GTI.getIndexedType()) * CIdx->getSExtValue();
455 GepHasConstantOffset = false;
457 uint64_t Scale = DL.getTypeAllocSize(GTI.getIndexedType());
458 unsigned ZExtBits = 0, SExtBits = 0;
460 // If the integer type is smaller than the pointer size, it is implicitly
461 // sign extended to pointer size.
462 unsigned Width = Index->getType()->getIntegerBitWidth();
463 if (PointerSize > Width)
464 SExtBits += PointerSize - Width;
466 // Use GetLinearExpression to decompose the index into a C1*V+C2 form.
467 APInt IndexScale(Width, 0), IndexOffset(Width, 0);
468 bool NSW = true, NUW = true;
469 Index = GetLinearExpression(Index, IndexScale, IndexOffset, ZExtBits,
470 SExtBits, DL, 0, AC, DT, NSW, NUW);
472 // The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale.
473 // This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.
474 Decomposed.OtherOffset += IndexOffset.getSExtValue() * Scale;
475 Scale *= IndexScale.getSExtValue();
477 // If we already had an occurrence of this index variable, merge this
478 // scale into it. For example, we want to handle:
479 // A[x][x] -> x*16 + x*4 -> x*20
480 // This also ensures that 'x' only appears in the index list once.
481 for (unsigned i = 0, e = Decomposed.VarIndices.size(); i != e; ++i) {
482 if (Decomposed.VarIndices[i].V == Index &&
483 Decomposed.VarIndices[i].ZExtBits == ZExtBits &&
484 Decomposed.VarIndices[i].SExtBits == SExtBits) {
485 Scale += Decomposed.VarIndices[i].Scale;
486 Decomposed.VarIndices.erase(Decomposed.VarIndices.begin() + i);
491 // Make sure that we have a scale that makes sense for this target's
493 Scale = adjustToPointerSize(Scale, PointerSize);
496 VariableGEPIndex Entry = {Index, ZExtBits, SExtBits,
497 static_cast<int64_t>(Scale)};
498 Decomposed.VarIndices.push_back(Entry);
502 // Take care of wrap-arounds
503 if (GepHasConstantOffset) {
504 Decomposed.StructOffset =
505 adjustToPointerSize(Decomposed.StructOffset, PointerSize);
506 Decomposed.OtherOffset =
507 adjustToPointerSize(Decomposed.OtherOffset, PointerSize);
510 // Analyze the base pointer next.
511 V = GEPOp->getOperand(0);
512 } while (--MaxLookup);
514 // If the chain of expressions is too deep, just return early.
516 SearchLimitReached++;
520 /// Returns whether the given pointer value points to memory that is local to
521 /// the function, with global constants being considered local to all
523 bool BasicAAResult::pointsToConstantMemory(const MemoryLocation &Loc,
525 assert(Visited.empty() && "Visited must be cleared after use!");
527 unsigned MaxLookup = 8;
528 SmallVector<const Value *, 16> Worklist;
529 Worklist.push_back(Loc.Ptr);
531 const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), DL);
532 if (!Visited.insert(V).second) {
534 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
537 // An alloca instruction defines local memory.
538 if (OrLocal && isa<AllocaInst>(V))
541 // A global constant counts as local memory for our purposes.
542 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
543 // Note: this doesn't require GV to be "ODR" because it isn't legal for a
544 // global to be marked constant in some modules and non-constant in
545 // others. GV may even be a declaration, not a definition.
546 if (!GV->isConstant()) {
548 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
553 // If both select values point to local memory, then so does the select.
554 if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
555 Worklist.push_back(SI->getTrueValue());
556 Worklist.push_back(SI->getFalseValue());
560 // If all values incoming to a phi node point to local memory, then so does
562 if (const PHINode *PN = dyn_cast<PHINode>(V)) {
563 // Don't bother inspecting phi nodes with many operands.
564 if (PN->getNumIncomingValues() > MaxLookup) {
566 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
568 for (Value *IncValue : PN->incoming_values())
569 Worklist.push_back(IncValue);
573 // Otherwise be conservative.
575 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
577 } while (!Worklist.empty() && --MaxLookup);
580 return Worklist.empty();
583 /// Returns the behavior when calling the given call site.
584 FunctionModRefBehavior BasicAAResult::getModRefBehavior(ImmutableCallSite CS) {
585 if (CS.doesNotAccessMemory())
586 // Can't do better than this.
587 return FMRB_DoesNotAccessMemory;
589 FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
591 // If the callsite knows it only reads memory, don't return worse
593 if (CS.onlyReadsMemory())
594 Min = FMRB_OnlyReadsMemory;
595 else if (CS.doesNotReadMemory())
596 Min = FMRB_DoesNotReadMemory;
598 if (CS.onlyAccessesArgMemory())
599 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
601 // If CS has operand bundles then aliasing attributes from the function it
602 // calls do not directly apply to the CallSite. This can be made more
603 // precise in the future.
604 if (!CS.hasOperandBundles())
605 if (const Function *F = CS.getCalledFunction())
607 FunctionModRefBehavior(Min & getBestAAResults().getModRefBehavior(F));
612 /// Returns the behavior when calling the given function. For use when the call
613 /// site is not known.
614 FunctionModRefBehavior BasicAAResult::getModRefBehavior(const Function *F) {
615 // If the function declares it doesn't access memory, we can't do better.
616 if (F->doesNotAccessMemory())
617 return FMRB_DoesNotAccessMemory;
619 FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
621 // If the function declares it only reads memory, go with that.
622 if (F->onlyReadsMemory())
623 Min = FMRB_OnlyReadsMemory;
624 else if (F->doesNotReadMemory())
625 Min = FMRB_DoesNotReadMemory;
627 if (F->onlyAccessesArgMemory())
628 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
629 else if (F->onlyAccessesInaccessibleMemory())
630 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesInaccessibleMem);
631 else if (F->onlyAccessesInaccessibleMemOrArgMem())
632 Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesInaccessibleOrArgMem);
637 /// Returns true if this is a writeonly (i.e Mod only) parameter.
638 static bool isWriteOnlyParam(ImmutableCallSite CS, unsigned ArgIdx,
639 const TargetLibraryInfo &TLI) {
640 if (CS.paramHasAttr(ArgIdx, Attribute::WriteOnly))
643 // We can bound the aliasing properties of memset_pattern16 just as we can
644 // for memcpy/memset. This is particularly important because the
645 // LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
646 // whenever possible.
647 // FIXME Consider handling this in InferFunctionAttr.cpp together with other
650 if (CS.getCalledFunction() && TLI.getLibFunc(*CS.getCalledFunction(), F) &&
651 F == LibFunc_memset_pattern16 && TLI.has(F))
655 // TODO: memset_pattern4, memset_pattern8
656 // TODO: _chk variants
657 // TODO: strcmp, strcpy
662 ModRefInfo BasicAAResult::getArgModRefInfo(ImmutableCallSite CS,
665 // Checking for known builtin intrinsics and target library functions.
666 if (isWriteOnlyParam(CS, ArgIdx, TLI))
669 if (CS.paramHasAttr(ArgIdx, Attribute::ReadOnly))
672 if (CS.paramHasAttr(ArgIdx, Attribute::ReadNone))
675 return AAResultBase::getArgModRefInfo(CS, ArgIdx);
678 static bool isIntrinsicCall(ImmutableCallSite CS, Intrinsic::ID IID) {
679 const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
680 return II && II->getIntrinsicID() == IID;
684 static const Function *getParent(const Value *V) {
685 if (const Instruction *inst = dyn_cast<Instruction>(V))
686 return inst->getParent()->getParent();
688 if (const Argument *arg = dyn_cast<Argument>(V))
689 return arg->getParent();
694 static bool notDifferentParent(const Value *O1, const Value *O2) {
696 const Function *F1 = getParent(O1);
697 const Function *F2 = getParent(O2);
699 return !F1 || !F2 || F1 == F2;
703 AliasResult BasicAAResult::alias(const MemoryLocation &LocA,
704 const MemoryLocation &LocB) {
705 assert(notDifferentParent(LocA.Ptr, LocB.Ptr) &&
706 "BasicAliasAnalysis doesn't support interprocedural queries.");
708 // If we have a directly cached entry for these locations, we have recursed
709 // through this once, so just return the cached results. Notably, when this
710 // happens, we don't clear the cache.
711 auto CacheIt = AliasCache.find(LocPair(LocA, LocB));
712 if (CacheIt != AliasCache.end())
713 return CacheIt->second;
715 AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.AATags, LocB.Ptr,
716 LocB.Size, LocB.AATags);
717 // AliasCache rarely has more than 1 or 2 elements, always use
718 // shrink_and_clear so it quickly returns to the inline capacity of the
719 // SmallDenseMap if it ever grows larger.
720 // FIXME: This should really be shrink_to_inline_capacity_and_clear().
721 AliasCache.shrink_and_clear();
722 VisitedPhiBBs.clear();
726 /// Checks to see if the specified callsite can clobber the specified memory
729 /// Since we only look at local properties of this function, we really can't
730 /// say much about this query. We do, however, use simple "address taken"
731 /// analysis on local objects.
732 ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS,
733 const MemoryLocation &Loc) {
734 assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
735 "AliasAnalysis query involving multiple functions!");
737 const Value *Object = GetUnderlyingObject(Loc.Ptr, DL);
739 // If this is a tail call and Loc.Ptr points to a stack location, we know that
740 // the tail call cannot access or modify the local stack.
741 // We cannot exclude byval arguments here; these belong to the caller of
742 // the current function not to the current function, and a tail callee
743 // may reference them.
744 if (isa<AllocaInst>(Object))
745 if (const CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
746 if (CI->isTailCall())
749 // If the pointer is to a locally allocated object that does not escape,
750 // then the call can not mod/ref the pointer unless the call takes the pointer
751 // as an argument, and itself doesn't capture it.
752 if (!isa<Constant>(Object) && CS.getInstruction() != Object &&
753 isNonEscapingLocalObject(Object)) {
755 // Optimistically assume that call doesn't touch Object and check this
756 // assumption in the following loop.
757 ModRefInfo Result = MRI_NoModRef;
759 unsigned OperandNo = 0;
760 for (auto CI = CS.data_operands_begin(), CE = CS.data_operands_end();
761 CI != CE; ++CI, ++OperandNo) {
762 // Only look at the no-capture or byval pointer arguments. If this
763 // pointer were passed to arguments that were neither of these, then it
764 // couldn't be no-capture.
765 if (!(*CI)->getType()->isPointerTy() ||
766 (!CS.doesNotCapture(OperandNo) &&
767 OperandNo < CS.getNumArgOperands() && !CS.isByValArgument(OperandNo)))
770 // Call doesn't access memory through this operand, so we don't care
771 // if it aliases with Object.
772 if (CS.doesNotAccessMemory(OperandNo))
775 // If this is a no-capture pointer argument, see if we can tell that it
776 // is impossible to alias the pointer we're checking.
778 getBestAAResults().alias(MemoryLocation(*CI), MemoryLocation(Object));
780 // Operand doesnt alias 'Object', continue looking for other aliases
783 // Operand aliases 'Object', but call doesn't modify it. Strengthen
784 // initial assumption and keep looking in case if there are more aliases.
785 if (CS.onlyReadsMemory(OperandNo)) {
786 Result = static_cast<ModRefInfo>(Result | MRI_Ref);
789 // Operand aliases 'Object' but call only writes into it.
790 if (CS.doesNotReadMemory(OperandNo)) {
791 Result = static_cast<ModRefInfo>(Result | MRI_Mod);
794 // This operand aliases 'Object' and call reads and writes into it.
799 // Early return if we improved mod ref information
800 if (Result != MRI_ModRef)
804 // If the CallSite is to malloc or calloc, we can assume that it doesn't
805 // modify any IR visible value. This is only valid because we assume these
806 // routines do not read values visible in the IR. TODO: Consider special
807 // casing realloc and strdup routines which access only their arguments as
808 // well. Or alternatively, replace all of this with inaccessiblememonly once
809 // that's implemented fully.
810 auto *Inst = CS.getInstruction();
811 if (isMallocOrCallocLikeFn(Inst, &TLI)) {
812 // Be conservative if the accessed pointer may alias the allocation -
813 // fallback to the generic handling below.
814 if (getBestAAResults().alias(MemoryLocation(Inst), Loc) == NoAlias)
818 // The semantics of memcpy intrinsics forbid overlap between their respective
819 // operands, i.e., source and destination of any given memcpy must no-alias.
820 // If Loc must-aliases either one of these two locations, then it necessarily
821 // no-aliases the other.
822 if (auto *Inst = dyn_cast<MemCpyInst>(CS.getInstruction())) {
823 AliasResult SrcAA, DestAA;
825 if ((SrcAA = getBestAAResults().alias(MemoryLocation::getForSource(Inst),
827 // Loc is exactly the memcpy source thus disjoint from memcpy dest.
829 if ((DestAA = getBestAAResults().alias(MemoryLocation::getForDest(Inst),
831 // The converse case.
834 // It's also possible for Loc to alias both src and dest, or neither.
835 ModRefInfo rv = MRI_NoModRef;
836 if (SrcAA != NoAlias)
837 rv = static_cast<ModRefInfo>(rv | MRI_Ref);
838 if (DestAA != NoAlias)
839 rv = static_cast<ModRefInfo>(rv | MRI_Mod);
843 // While the assume intrinsic is marked as arbitrarily writing so that
844 // proper control dependencies will be maintained, it never aliases any
845 // particular memory location.
846 if (isIntrinsicCall(CS, Intrinsic::assume))
849 // Like assumes, guard intrinsics are also marked as arbitrarily writing so
850 // that proper control dependencies are maintained but they never mods any
851 // particular memory location.
853 // *Unlike* assumes, guard intrinsics are modeled as reading memory since the
854 // heap state at the point the guard is issued needs to be consistent in case
855 // the guard invokes the "deopt" continuation.
856 if (isIntrinsicCall(CS, Intrinsic::experimental_guard))
859 // Like assumes, invariant.start intrinsics were also marked as arbitrarily
860 // writing so that proper control dependencies are maintained but they never
861 // mod any particular memory location visible to the IR.
862 // *Unlike* assumes (which are now modeled as NoModRef), invariant.start
863 // intrinsic is now modeled as reading memory. This prevents hoisting the
864 // invariant.start intrinsic over stores. Consider:
867 // invariant_start(ptr)
871 // This cannot be transformed to:
874 // invariant_start(ptr)
879 // The transformation will cause the second store to be ignored (based on
880 // rules of invariant.start) and print 40, while the first program always
882 if (isIntrinsicCall(CS, Intrinsic::invariant_start))
885 // The AAResultBase base class has some smarts, lets use them.
886 return AAResultBase::getModRefInfo(CS, Loc);
889 ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS1,
890 ImmutableCallSite CS2) {
891 // While the assume intrinsic is marked as arbitrarily writing so that
892 // proper control dependencies will be maintained, it never aliases any
893 // particular memory location.
894 if (isIntrinsicCall(CS1, Intrinsic::assume) ||
895 isIntrinsicCall(CS2, Intrinsic::assume))
898 // Like assumes, guard intrinsics are also marked as arbitrarily writing so
899 // that proper control dependencies are maintained but they never mod any
900 // particular memory location.
902 // *Unlike* assumes, guard intrinsics are modeled as reading memory since the
903 // heap state at the point the guard is issued needs to be consistent in case
904 // the guard invokes the "deopt" continuation.
906 // NB! This function is *not* commutative, so we specical case two
907 // possibilities for guard intrinsics.
909 if (isIntrinsicCall(CS1, Intrinsic::experimental_guard))
910 return getModRefBehavior(CS2) & MRI_Mod ? MRI_Ref : MRI_NoModRef;
912 if (isIntrinsicCall(CS2, Intrinsic::experimental_guard))
913 return getModRefBehavior(CS1) & MRI_Mod ? MRI_Mod : MRI_NoModRef;
915 // The AAResultBase base class has some smarts, lets use them.
916 return AAResultBase::getModRefInfo(CS1, CS2);
919 /// Provide ad-hoc rules to disambiguate accesses through two GEP operators,
920 /// both having the exact same pointer operand.
921 static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
923 const GEPOperator *GEP2,
925 const DataLayout &DL) {
927 assert(GEP1->getPointerOperand()->stripPointerCasts() ==
928 GEP2->getPointerOperand()->stripPointerCasts() &&
929 GEP1->getPointerOperandType() == GEP2->getPointerOperandType() &&
930 "Expected GEPs with the same pointer operand");
932 // Try to determine whether GEP1 and GEP2 index through arrays, into structs,
933 // such that the struct field accesses provably cannot alias.
934 // We also need at least two indices (the pointer, and the struct field).
935 if (GEP1->getNumIndices() != GEP2->getNumIndices() ||
936 GEP1->getNumIndices() < 2)
939 // If we don't know the size of the accesses through both GEPs, we can't
940 // determine whether the struct fields accessed can't alias.
941 if (V1Size == MemoryLocation::UnknownSize ||
942 V2Size == MemoryLocation::UnknownSize)
946 dyn_cast<ConstantInt>(GEP1->getOperand(GEP1->getNumOperands() - 1));
948 dyn_cast<ConstantInt>(GEP2->getOperand(GEP2->getNumOperands() - 1));
950 // If the last (struct) indices are constants and are equal, the other indices
951 // might be also be dynamically equal, so the GEPs can alias.
952 if (C1 && C2 && C1->getSExtValue() == C2->getSExtValue())
955 // Find the last-indexed type of the GEP, i.e., the type you'd get if
956 // you stripped the last index.
957 // On the way, look at each indexed type. If there's something other
958 // than an array, different indices can lead to different final types.
959 SmallVector<Value *, 8> IntermediateIndices;
961 // Insert the first index; we don't need to check the type indexed
962 // through it as it only drops the pointer indirection.
963 assert(GEP1->getNumIndices() > 1 && "Not enough GEP indices to examine");
964 IntermediateIndices.push_back(GEP1->getOperand(1));
966 // Insert all the remaining indices but the last one.
967 // Also, check that they all index through arrays.
968 for (unsigned i = 1, e = GEP1->getNumIndices() - 1; i != e; ++i) {
969 if (!isa<ArrayType>(GetElementPtrInst::getIndexedType(
970 GEP1->getSourceElementType(), IntermediateIndices)))
972 IntermediateIndices.push_back(GEP1->getOperand(i + 1));
975 auto *Ty = GetElementPtrInst::getIndexedType(
976 GEP1->getSourceElementType(), IntermediateIndices);
977 StructType *LastIndexedStruct = dyn_cast<StructType>(Ty);
979 if (isa<SequentialType>(Ty)) {
981 // - both GEPs begin indexing from the exact same pointer;
982 // - the last indices in both GEPs are constants, indexing into a sequential
983 // type (array or pointer);
984 // - both GEPs only index through arrays prior to that.
986 // Because array indices greater than the number of elements are valid in
987 // GEPs, unless we know the intermediate indices are identical between
988 // GEP1 and GEP2 we cannot guarantee that the last indexed arrays don't
989 // partially overlap. We also need to check that the loaded size matches
990 // the element size, otherwise we could still have overlap.
991 const uint64_t ElementSize =
992 DL.getTypeStoreSize(cast<SequentialType>(Ty)->getElementType());
993 if (V1Size != ElementSize || V2Size != ElementSize)
996 for (unsigned i = 0, e = GEP1->getNumIndices() - 1; i != e; ++i)
997 if (GEP1->getOperand(i + 1) != GEP2->getOperand(i + 1))
1000 // Now we know that the array/pointer that GEP1 indexes into and that
1001 // that GEP2 indexes into must either precisely overlap or be disjoint.
1002 // Because they cannot partially overlap and because fields in an array
1003 // cannot overlap, if we can prove the final indices are different between
1004 // GEP1 and GEP2, we can conclude GEP1 and GEP2 don't alias.
1006 // If the last indices are constants, we've already checked they don't
1007 // equal each other so we can exit early.
1010 if (isKnownNonEqual(GEP1->getOperand(GEP1->getNumOperands() - 1),
1011 GEP2->getOperand(GEP2->getNumOperands() - 1),
1015 } else if (!LastIndexedStruct || !C1 || !C2) {
1020 // - both GEPs begin indexing from the exact same pointer;
1021 // - the last indices in both GEPs are constants, indexing into a struct;
1022 // - said indices are different, hence, the pointed-to fields are different;
1023 // - both GEPs only index through arrays prior to that.
1025 // This lets us determine that the struct that GEP1 indexes into and the
1026 // struct that GEP2 indexes into must either precisely overlap or be
1027 // completely disjoint. Because they cannot partially overlap, indexing into
1028 // different non-overlapping fields of the struct will never alias.
1030 // Therefore, the only remaining thing needed to show that both GEPs can't
1031 // alias is that the fields are not overlapping.
1032 const StructLayout *SL = DL.getStructLayout(LastIndexedStruct);
1033 const uint64_t StructSize = SL->getSizeInBytes();
1034 const uint64_t V1Off = SL->getElementOffset(C1->getZExtValue());
1035 const uint64_t V2Off = SL->getElementOffset(C2->getZExtValue());
1037 auto EltsDontOverlap = [StructSize](uint64_t V1Off, uint64_t V1Size,
1038 uint64_t V2Off, uint64_t V2Size) {
1039 return V1Off < V2Off && V1Off + V1Size <= V2Off &&
1040 ((V2Off + V2Size <= StructSize) ||
1041 (V2Off + V2Size - StructSize <= V1Off));
1044 if (EltsDontOverlap(V1Off, V1Size, V2Off, V2Size) ||
1045 EltsDontOverlap(V2Off, V2Size, V1Off, V1Size))
1051 // If a we have (a) a GEP and (b) a pointer based on an alloca, and the
1052 // beginning of the object the GEP points would have a negative offset with
1053 // repsect to the alloca, that means the GEP can not alias pointer (b).
1054 // Note that the pointer based on the alloca may not be a GEP. For
1055 // example, it may be the alloca itself.
1056 // The same applies if (b) is based on a GlobalVariable. Note that just being
1057 // based on isIdentifiedObject() is not enough - we need an identified object
1058 // that does not permit access to negative offsets. For example, a negative
1059 // offset from a noalias argument or call can be inbounds w.r.t the actual
1060 // underlying object.
1062 // For example, consider:
1064 // struct { int f0, int f1, ...} foo;
1066 // foo* random = bar(alloca);
1067 // int *f0 = &alloca.f0
1068 // int *f1 = &random->f1;
1070 // Which is lowered, approximately, to:
1072 // %alloca = alloca %struct.foo
1073 // %random = call %struct.foo* @random(%struct.foo* %alloca)
1074 // %f0 = getelementptr inbounds %struct, %struct.foo* %alloca, i32 0, i32 0
1075 // %f1 = getelementptr inbounds %struct, %struct.foo* %random, i32 0, i32 1
1077 // Assume %f1 and %f0 alias. Then %f1 would point into the object allocated
1078 // by %alloca. Since the %f1 GEP is inbounds, that means %random must also
1079 // point into the same object. But since %f0 points to the beginning of %alloca,
1080 // the highest %f1 can be is (%alloca + 3). This means %random can not be higher
1081 // than (%alloca - 1), and so is not inbounds, a contradiction.
1082 bool BasicAAResult::isGEPBaseAtNegativeOffset(const GEPOperator *GEPOp,
1083 const DecomposedGEP &DecompGEP, const DecomposedGEP &DecompObject,
1084 uint64_t ObjectAccessSize) {
1085 // If the object access size is unknown, or the GEP isn't inbounds, bail.
1086 if (ObjectAccessSize == MemoryLocation::UnknownSize || !GEPOp->isInBounds())
1089 // We need the object to be an alloca or a globalvariable, and want to know
1090 // the offset of the pointer from the object precisely, so no variable
1091 // indices are allowed.
1092 if (!(isa<AllocaInst>(DecompObject.Base) ||
1093 isa<GlobalVariable>(DecompObject.Base)) ||
1094 !DecompObject.VarIndices.empty())
1097 int64_t ObjectBaseOffset = DecompObject.StructOffset +
1098 DecompObject.OtherOffset;
1100 // If the GEP has no variable indices, we know the precise offset
1101 // from the base, then use it. If the GEP has variable indices, we're in
1102 // a bit more trouble: we can't count on the constant offsets that come
1103 // from non-struct sources, since these can be "rewound" by a negative
1104 // variable offset. So use only offsets that came from structs.
1105 int64_t GEPBaseOffset = DecompGEP.StructOffset;
1106 if (DecompGEP.VarIndices.empty())
1107 GEPBaseOffset += DecompGEP.OtherOffset;
1109 return (GEPBaseOffset >= ObjectBaseOffset + (int64_t)ObjectAccessSize);
1112 /// Provides a bunch of ad-hoc rules to disambiguate a GEP instruction against
1113 /// another pointer.
1115 /// We know that V1 is a GEP, but we don't know anything about V2.
1116 /// UnderlyingV1 is GetUnderlyingObject(GEP1, DL), UnderlyingV2 is the same for
1118 AliasResult BasicAAResult::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
1119 const AAMDNodes &V1AAInfo, const Value *V2,
1120 uint64_t V2Size, const AAMDNodes &V2AAInfo,
1121 const Value *UnderlyingV1,
1122 const Value *UnderlyingV2) {
1123 DecomposedGEP DecompGEP1, DecompGEP2;
1124 bool GEP1MaxLookupReached =
1125 DecomposeGEPExpression(GEP1, DecompGEP1, DL, &AC, DT);
1126 bool GEP2MaxLookupReached =
1127 DecomposeGEPExpression(V2, DecompGEP2, DL, &AC, DT);
1129 int64_t GEP1BaseOffset = DecompGEP1.StructOffset + DecompGEP1.OtherOffset;
1130 int64_t GEP2BaseOffset = DecompGEP2.StructOffset + DecompGEP2.OtherOffset;
1132 assert(DecompGEP1.Base == UnderlyingV1 && DecompGEP2.Base == UnderlyingV2 &&
1133 "DecomposeGEPExpression returned a result different from "
1134 "GetUnderlyingObject");
1136 // If the GEP's offset relative to its base is such that the base would
1137 // fall below the start of the object underlying V2, then the GEP and V2
1139 if (!GEP1MaxLookupReached && !GEP2MaxLookupReached &&
1140 isGEPBaseAtNegativeOffset(GEP1, DecompGEP1, DecompGEP2, V2Size))
1142 // If we have two gep instructions with must-alias or not-alias'ing base
1143 // pointers, figure out if the indexes to the GEP tell us anything about the
1145 if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
1146 // Check for the GEP base being at a negative offset, this time in the other
1148 if (!GEP1MaxLookupReached && !GEP2MaxLookupReached &&
1149 isGEPBaseAtNegativeOffset(GEP2, DecompGEP2, DecompGEP1, V1Size))
1151 // Do the base pointers alias?
1152 AliasResult BaseAlias =
1153 aliasCheck(UnderlyingV1, MemoryLocation::UnknownSize, AAMDNodes(),
1154 UnderlyingV2, MemoryLocation::UnknownSize, AAMDNodes());
1156 // Check for geps of non-aliasing underlying pointers where the offsets are
1158 if ((BaseAlias == MayAlias) && V1Size == V2Size) {
1159 // Do the base pointers alias assuming type and size.
1160 AliasResult PreciseBaseAlias = aliasCheck(UnderlyingV1, V1Size, V1AAInfo,
1161 UnderlyingV2, V2Size, V2AAInfo);
1162 if (PreciseBaseAlias == NoAlias) {
1163 // See if the computed offset from the common pointer tells us about the
1164 // relation of the resulting pointer.
1165 // If the max search depth is reached the result is undefined
1166 if (GEP2MaxLookupReached || GEP1MaxLookupReached)
1170 if (GEP1BaseOffset == GEP2BaseOffset &&
1171 DecompGEP1.VarIndices == DecompGEP2.VarIndices)
1176 // If we get a No or May, then return it immediately, no amount of analysis
1177 // will improve this situation.
1178 if (BaseAlias != MustAlias)
1181 // Otherwise, we have a MustAlias. Since the base pointers alias each other
1182 // exactly, see if the computed offset from the common pointer tells us
1183 // about the relation of the resulting pointer.
1184 // If we know the two GEPs are based off of the exact same pointer (and not
1185 // just the same underlying object), see if that tells us anything about
1186 // the resulting pointers.
1187 if (GEP1->getPointerOperand()->stripPointerCasts() ==
1188 GEP2->getPointerOperand()->stripPointerCasts() &&
1189 GEP1->getPointerOperandType() == GEP2->getPointerOperandType()) {
1190 AliasResult R = aliasSameBasePointerGEPs(GEP1, V1Size, GEP2, V2Size, DL);
1191 // If we couldn't find anything interesting, don't abandon just yet.
1196 // If the max search depth is reached, the result is undefined
1197 if (GEP2MaxLookupReached || GEP1MaxLookupReached)
1200 // Subtract the GEP2 pointer from the GEP1 pointer to find out their
1201 // symbolic difference.
1202 GEP1BaseOffset -= GEP2BaseOffset;
1203 GetIndexDifference(DecompGEP1.VarIndices, DecompGEP2.VarIndices);
1206 // Check to see if these two pointers are related by the getelementptr
1207 // instruction. If one pointer is a GEP with a non-zero index of the other
1208 // pointer, we know they cannot alias.
1210 // If both accesses are unknown size, we can't do anything useful here.
1211 if (V1Size == MemoryLocation::UnknownSize &&
1212 V2Size == MemoryLocation::UnknownSize)
1215 AliasResult R = aliasCheck(UnderlyingV1, MemoryLocation::UnknownSize,
1216 AAMDNodes(), V2, MemoryLocation::UnknownSize,
1217 V2AAInfo, nullptr, UnderlyingV2);
1219 // If V2 may alias GEP base pointer, conservatively returns MayAlias.
1220 // If V2 is known not to alias GEP base pointer, then the two values
1221 // cannot alias per GEP semantics: "Any memory access must be done through
1222 // a pointer value associated with an address range of the memory access,
1223 // otherwise the behavior is undefined.".
1226 // If the max search depth is reached the result is undefined
1227 if (GEP1MaxLookupReached)
1231 // In the two GEP Case, if there is no difference in the offsets of the
1232 // computed pointers, the resultant pointers are a must alias. This
1233 // happens when we have two lexically identical GEP's (for example).
1235 // In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
1236 // must aliases the GEP, the end result is a must alias also.
1237 if (GEP1BaseOffset == 0 && DecompGEP1.VarIndices.empty())
1240 // If there is a constant difference between the pointers, but the difference
1241 // is less than the size of the associated memory object, then we know
1242 // that the objects are partially overlapping. If the difference is
1243 // greater, we know they do not overlap.
1244 if (GEP1BaseOffset != 0 && DecompGEP1.VarIndices.empty()) {
1245 if (GEP1BaseOffset >= 0) {
1246 if (V2Size != MemoryLocation::UnknownSize) {
1247 if ((uint64_t)GEP1BaseOffset < V2Size)
1248 return PartialAlias;
1252 // We have the situation where:
1255 // ---------------->|
1256 // |-->V1Size |-------> V2Size
1258 // We need to know that V2Size is not unknown, otherwise we might have
1259 // stripped a gep with negative index ('gep <ptr>, -1, ...).
1260 if (V1Size != MemoryLocation::UnknownSize &&
1261 V2Size != MemoryLocation::UnknownSize) {
1262 if (-(uint64_t)GEP1BaseOffset < V1Size)
1263 return PartialAlias;
1269 if (!DecompGEP1.VarIndices.empty()) {
1270 uint64_t Modulo = 0;
1271 bool AllPositive = true;
1272 for (unsigned i = 0, e = DecompGEP1.VarIndices.size(); i != e; ++i) {
1274 // Try to distinguish something like &A[i][1] against &A[42][0].
1275 // Grab the least significant bit set in any of the scales. We
1276 // don't need std::abs here (even if the scale's negative) as we'll
1277 // be ^'ing Modulo with itself later.
1278 Modulo |= (uint64_t)DecompGEP1.VarIndices[i].Scale;
1281 // If the Value could change between cycles, then any reasoning about
1282 // the Value this cycle may not hold in the next cycle. We'll just
1283 // give up if we can't determine conditions that hold for every cycle:
1284 const Value *V = DecompGEP1.VarIndices[i].V;
1286 bool SignKnownZero, SignKnownOne;
1287 ComputeSignBit(const_cast<Value *>(V), SignKnownZero, SignKnownOne, DL,
1288 0, &AC, nullptr, DT);
1290 // Zero-extension widens the variable, and so forces the sign
1292 bool IsZExt = DecompGEP1.VarIndices[i].ZExtBits > 0 || isa<ZExtInst>(V);
1293 SignKnownZero |= IsZExt;
1294 SignKnownOne &= !IsZExt;
1296 // If the variable begins with a zero then we know it's
1297 // positive, regardless of whether the value is signed or
1299 int64_t Scale = DecompGEP1.VarIndices[i].Scale;
1301 (SignKnownZero && Scale >= 0) || (SignKnownOne && Scale < 0);
1305 Modulo = Modulo ^ (Modulo & (Modulo - 1));
1307 // We can compute the difference between the two addresses
1308 // mod Modulo. Check whether that difference guarantees that the
1309 // two locations do not alias.
1310 uint64_t ModOffset = (uint64_t)GEP1BaseOffset & (Modulo - 1);
1311 if (V1Size != MemoryLocation::UnknownSize &&
1312 V2Size != MemoryLocation::UnknownSize && ModOffset >= V2Size &&
1313 V1Size <= Modulo - ModOffset)
1316 // If we know all the variables are positive, then GEP1 >= GEP1BasePtr.
1317 // If GEP1BasePtr > V2 (GEP1BaseOffset > 0) then we know the pointers
1318 // don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
1319 if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t)GEP1BaseOffset)
1322 if (constantOffsetHeuristic(DecompGEP1.VarIndices, V1Size, V2Size,
1323 GEP1BaseOffset, &AC, DT))
1327 // Statically, we can see that the base objects are the same, but the
1328 // pointers have dynamic offsets which we can't resolve. And none of our
1329 // little tricks above worked.
1331 // TODO: Returning PartialAlias instead of MayAlias is a mild hack; the
1332 // practical effect of this is protecting TBAA in the case of dynamic
1333 // indices into arrays of unions or malloc'd memory.
1334 return PartialAlias;
1337 static AliasResult MergeAliasResults(AliasResult A, AliasResult B) {
1338 // If the results agree, take it.
1341 // A mix of PartialAlias and MustAlias is PartialAlias.
1342 if ((A == PartialAlias && B == MustAlias) ||
1343 (B == PartialAlias && A == MustAlias))
1344 return PartialAlias;
1345 // Otherwise, we don't know anything.
1349 /// Provides a bunch of ad-hoc rules to disambiguate a Select instruction
1350 /// against another.
1351 AliasResult BasicAAResult::aliasSelect(const SelectInst *SI, uint64_t SISize,
1352 const AAMDNodes &SIAAInfo,
1353 const Value *V2, uint64_t V2Size,
1354 const AAMDNodes &V2AAInfo,
1355 const Value *UnderV2) {
1356 // If the values are Selects with the same condition, we can do a more precise
1357 // check: just check for aliases between the values on corresponding arms.
1358 if (const SelectInst *SI2 = dyn_cast<SelectInst>(V2))
1359 if (SI->getCondition() == SI2->getCondition()) {
1360 AliasResult Alias = aliasCheck(SI->getTrueValue(), SISize, SIAAInfo,
1361 SI2->getTrueValue(), V2Size, V2AAInfo);
1362 if (Alias == MayAlias)
1364 AliasResult ThisAlias =
1365 aliasCheck(SI->getFalseValue(), SISize, SIAAInfo,
1366 SI2->getFalseValue(), V2Size, V2AAInfo);
1367 return MergeAliasResults(ThisAlias, Alias);
1370 // If both arms of the Select node NoAlias or MustAlias V2, then returns
1371 // NoAlias / MustAlias. Otherwise, returns MayAlias.
1373 aliasCheck(V2, V2Size, V2AAInfo, SI->getTrueValue(),
1374 SISize, SIAAInfo, UnderV2);
1375 if (Alias == MayAlias)
1378 AliasResult ThisAlias =
1379 aliasCheck(V2, V2Size, V2AAInfo, SI->getFalseValue(), SISize, SIAAInfo,
1381 return MergeAliasResults(ThisAlias, Alias);
1384 /// Provide a bunch of ad-hoc rules to disambiguate a PHI instruction against
1386 AliasResult BasicAAResult::aliasPHI(const PHINode *PN, uint64_t PNSize,
1387 const AAMDNodes &PNAAInfo, const Value *V2,
1388 uint64_t V2Size, const AAMDNodes &V2AAInfo,
1389 const Value *UnderV2) {
1390 // Track phi nodes we have visited. We use this information when we determine
1391 // value equivalence.
1392 VisitedPhiBBs.insert(PN->getParent());
1394 // If the values are PHIs in the same block, we can do a more precise
1395 // as well as efficient check: just check for aliases between the values
1396 // on corresponding edges.
1397 if (const PHINode *PN2 = dyn_cast<PHINode>(V2))
1398 if (PN2->getParent() == PN->getParent()) {
1399 LocPair Locs(MemoryLocation(PN, PNSize, PNAAInfo),
1400 MemoryLocation(V2, V2Size, V2AAInfo));
1402 std::swap(Locs.first, Locs.second);
1403 // Analyse the PHIs' inputs under the assumption that the PHIs are
1405 // If the PHIs are May/MustAlias there must be (recursively) an input
1406 // operand from outside the PHIs' cycle that is MayAlias/MustAlias or
1407 // there must be an operation on the PHIs within the PHIs' value cycle
1408 // that causes a MayAlias.
1409 // Pretend the phis do not alias.
1410 AliasResult Alias = NoAlias;
1411 assert(AliasCache.count(Locs) &&
1412 "There must exist an entry for the phi node");
1413 AliasResult OrigAliasResult = AliasCache[Locs];
1414 AliasCache[Locs] = NoAlias;
1416 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1417 AliasResult ThisAlias =
1418 aliasCheck(PN->getIncomingValue(i), PNSize, PNAAInfo,
1419 PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
1421 Alias = MergeAliasResults(ThisAlias, Alias);
1422 if (Alias == MayAlias)
1426 // Reset if speculation failed.
1427 if (Alias != NoAlias)
1428 AliasCache[Locs] = OrigAliasResult;
1433 SmallPtrSet<Value *, 4> UniqueSrc;
1434 SmallVector<Value *, 4> V1Srcs;
1435 bool isRecursive = false;
1436 for (Value *PV1 : PN->incoming_values()) {
1437 if (isa<PHINode>(PV1))
1438 // If any of the source itself is a PHI, return MayAlias conservatively
1439 // to avoid compile time explosion. The worst possible case is if both
1440 // sides are PHI nodes. In which case, this is O(m x n) time where 'm'
1441 // and 'n' are the number of PHI sources.
1444 if (EnableRecPhiAnalysis)
1445 if (GEPOperator *PV1GEP = dyn_cast<GEPOperator>(PV1)) {
1446 // Check whether the incoming value is a GEP that advances the pointer
1447 // result of this PHI node (e.g. in a loop). If this is the case, we
1448 // would recurse and always get a MayAlias. Handle this case specially
1450 if (PV1GEP->getPointerOperand() == PN && PV1GEP->getNumIndices() == 1 &&
1451 isa<ConstantInt>(PV1GEP->idx_begin())) {
1457 if (UniqueSrc.insert(PV1).second)
1458 V1Srcs.push_back(PV1);
1461 // If this PHI node is recursive, set the size of the accessed memory to
1462 // unknown to represent all the possible values the GEP could advance the
1465 PNSize = MemoryLocation::UnknownSize;
1468 aliasCheck(V2, V2Size, V2AAInfo, V1Srcs[0],
1469 PNSize, PNAAInfo, UnderV2);
1471 // Early exit if the check of the first PHI source against V2 is MayAlias.
1472 // Other results are not possible.
1473 if (Alias == MayAlias)
1476 // If all sources of the PHI node NoAlias or MustAlias V2, then returns
1477 // NoAlias / MustAlias. Otherwise, returns MayAlias.
1478 for (unsigned i = 1, e = V1Srcs.size(); i != e; ++i) {
1479 Value *V = V1Srcs[i];
1481 AliasResult ThisAlias =
1482 aliasCheck(V2, V2Size, V2AAInfo, V, PNSize, PNAAInfo, UnderV2);
1483 Alias = MergeAliasResults(ThisAlias, Alias);
1484 if (Alias == MayAlias)
1491 /// Provides a bunch of ad-hoc rules to disambiguate in common cases, such as
1492 /// array references.
1493 AliasResult BasicAAResult::aliasCheck(const Value *V1, uint64_t V1Size,
1494 AAMDNodes V1AAInfo, const Value *V2,
1495 uint64_t V2Size, AAMDNodes V2AAInfo,
1496 const Value *O1, const Value *O2) {
1497 // If either of the memory references is empty, it doesn't matter what the
1498 // pointer values are.
1499 if (V1Size == 0 || V2Size == 0)
1502 // Strip off any casts if they exist.
1503 V1 = V1->stripPointerCasts();
1504 V2 = V2->stripPointerCasts();
1506 // If V1 or V2 is undef, the result is NoAlias because we can always pick a
1507 // value for undef that aliases nothing in the program.
1508 if (isa<UndefValue>(V1) || isa<UndefValue>(V2))
1511 // Are we checking for alias of the same value?
1512 // Because we look 'through' phi nodes, we could look at "Value" pointers from
1513 // different iterations. We must therefore make sure that this is not the
1514 // case. The function isValueEqualInPotentialCycles ensures that this cannot
1515 // happen by looking at the visited phi nodes and making sure they cannot
1517 if (isValueEqualInPotentialCycles(V1, V2))
1520 if (!V1->getType()->isPointerTy() || !V2->getType()->isPointerTy())
1521 return NoAlias; // Scalars cannot alias each other
1523 // Figure out what objects these things are pointing to if we can.
1525 O1 = GetUnderlyingObject(V1, DL, MaxLookupSearchDepth);
1528 O2 = GetUnderlyingObject(V2, DL, MaxLookupSearchDepth);
1530 // Null values in the default address space don't point to any object, so they
1531 // don't alias any other pointer.
1532 if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O1))
1533 if (CPN->getType()->getAddressSpace() == 0)
1535 if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O2))
1536 if (CPN->getType()->getAddressSpace() == 0)
1540 // If V1/V2 point to two different objects, we know that we have no alias.
1541 if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
1544 // Constant pointers can't alias with non-const isIdentifiedObject objects.
1545 if ((isa<Constant>(O1) && isIdentifiedObject(O2) && !isa<Constant>(O2)) ||
1546 (isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
1549 // Function arguments can't alias with things that are known to be
1550 // unambigously identified at the function level.
1551 if ((isa<Argument>(O1) && isIdentifiedFunctionLocal(O2)) ||
1552 (isa<Argument>(O2) && isIdentifiedFunctionLocal(O1)))
1555 // Most objects can't alias null.
1556 if ((isa<ConstantPointerNull>(O2) && isKnownNonNull(O1)) ||
1557 (isa<ConstantPointerNull>(O1) && isKnownNonNull(O2)))
1560 // If one pointer is the result of a call/invoke or load and the other is a
1561 // non-escaping local object within the same function, then we know the
1562 // object couldn't escape to a point where the call could return it.
1564 // Note that if the pointers are in different functions, there are a
1565 // variety of complications. A call with a nocapture argument may still
1566 // temporary store the nocapture argument's value in a temporary memory
1567 // location if that memory location doesn't escape. Or it may pass a
1568 // nocapture value to other functions as long as they don't capture it.
1569 if (isEscapeSource(O1) && isNonEscapingLocalObject(O2))
1571 if (isEscapeSource(O2) && isNonEscapingLocalObject(O1))
1575 // If the size of one access is larger than the entire object on the other
1576 // side, then we know such behavior is undefined and can assume no alias.
1577 if ((V1Size != MemoryLocation::UnknownSize &&
1578 isObjectSmallerThan(O2, V1Size, DL, TLI)) ||
1579 (V2Size != MemoryLocation::UnknownSize &&
1580 isObjectSmallerThan(O1, V2Size, DL, TLI)))
1583 // Check the cache before climbing up use-def chains. This also terminates
1584 // otherwise infinitely recursive queries.
1585 LocPair Locs(MemoryLocation(V1, V1Size, V1AAInfo),
1586 MemoryLocation(V2, V2Size, V2AAInfo));
1588 std::swap(Locs.first, Locs.second);
1589 std::pair<AliasCacheTy::iterator, bool> Pair =
1590 AliasCache.insert(std::make_pair(Locs, MayAlias));
1592 return Pair.first->second;
1594 // FIXME: This isn't aggressively handling alias(GEP, PHI) for example: if the
1595 // GEP can't simplify, we don't even look at the PHI cases.
1596 if (!isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
1598 std::swap(V1Size, V2Size);
1600 std::swap(V1AAInfo, V2AAInfo);
1602 if (const GEPOperator *GV1 = dyn_cast<GEPOperator>(V1)) {
1603 AliasResult Result =
1604 aliasGEP(GV1, V1Size, V1AAInfo, V2, V2Size, V2AAInfo, O1, O2);
1605 if (Result != MayAlias)
1606 return AliasCache[Locs] = Result;
1609 if (isa<PHINode>(V2) && !isa<PHINode>(V1)) {
1612 std::swap(V1Size, V2Size);
1613 std::swap(V1AAInfo, V2AAInfo);
1615 if (const PHINode *PN = dyn_cast<PHINode>(V1)) {
1616 AliasResult Result = aliasPHI(PN, V1Size, V1AAInfo,
1617 V2, V2Size, V2AAInfo, O2);
1618 if (Result != MayAlias)
1619 return AliasCache[Locs] = Result;
1622 if (isa<SelectInst>(V2) && !isa<SelectInst>(V1)) {
1625 std::swap(V1Size, V2Size);
1626 std::swap(V1AAInfo, V2AAInfo);
1628 if (const SelectInst *S1 = dyn_cast<SelectInst>(V1)) {
1629 AliasResult Result =
1630 aliasSelect(S1, V1Size, V1AAInfo, V2, V2Size, V2AAInfo, O2);
1631 if (Result != MayAlias)
1632 return AliasCache[Locs] = Result;
1635 // If both pointers are pointing into the same object and one of them
1636 // accesses the entire object, then the accesses must overlap in some way.
1638 if ((V1Size != MemoryLocation::UnknownSize &&
1639 isObjectSize(O1, V1Size, DL, TLI)) ||
1640 (V2Size != MemoryLocation::UnknownSize &&
1641 isObjectSize(O2, V2Size, DL, TLI)))
1642 return AliasCache[Locs] = PartialAlias;
1644 // Recurse back into the best AA results we have, potentially with refined
1645 // memory locations. We have already ensured that BasicAA has a MayAlias
1646 // cache result for these, so any recursion back into BasicAA won't loop.
1647 AliasResult Result = getBestAAResults().alias(Locs.first, Locs.second);
1648 return AliasCache[Locs] = Result;
1651 /// Check whether two Values can be considered equivalent.
1653 /// In addition to pointer equivalence of \p V1 and \p V2 this checks whether
1654 /// they can not be part of a cycle in the value graph by looking at all
1655 /// visited phi nodes an making sure that the phis cannot reach the value. We
1656 /// have to do this because we are looking through phi nodes (That is we say
1657 /// noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
1658 bool BasicAAResult::isValueEqualInPotentialCycles(const Value *V,
1663 const Instruction *Inst = dyn_cast<Instruction>(V);
1667 if (VisitedPhiBBs.empty())
1670 if (VisitedPhiBBs.size() > MaxNumPhiBBsValueReachabilityCheck)
1673 // Make sure that the visited phis cannot reach the Value. This ensures that
1674 // the Values cannot come from different iterations of a potential cycle the
1675 // phi nodes could be involved in.
1676 for (auto *P : VisitedPhiBBs)
1677 if (isPotentiallyReachable(&P->front(), Inst, DT, LI))
1683 /// Computes the symbolic difference between two de-composed GEPs.
1685 /// Dest and Src are the variable indices from two decomposed GetElementPtr
1686 /// instructions GEP1 and GEP2 which have common base pointers.
1687 void BasicAAResult::GetIndexDifference(
1688 SmallVectorImpl<VariableGEPIndex> &Dest,
1689 const SmallVectorImpl<VariableGEPIndex> &Src) {
1693 for (unsigned i = 0, e = Src.size(); i != e; ++i) {
1694 const Value *V = Src[i].V;
1695 unsigned ZExtBits = Src[i].ZExtBits, SExtBits = Src[i].SExtBits;
1696 int64_t Scale = Src[i].Scale;
1698 // Find V in Dest. This is N^2, but pointer indices almost never have more
1699 // than a few variable indexes.
1700 for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
1701 if (!isValueEqualInPotentialCycles(Dest[j].V, V) ||
1702 Dest[j].ZExtBits != ZExtBits || Dest[j].SExtBits != SExtBits)
1705 // If we found it, subtract off Scale V's from the entry in Dest. If it
1706 // goes to zero, remove the entry.
1707 if (Dest[j].Scale != Scale)
1708 Dest[j].Scale -= Scale;
1710 Dest.erase(Dest.begin() + j);
1715 // If we didn't consume this entry, add it to the end of the Dest list.
1717 VariableGEPIndex Entry = {V, ZExtBits, SExtBits, -Scale};
1718 Dest.push_back(Entry);
1723 bool BasicAAResult::constantOffsetHeuristic(
1724 const SmallVectorImpl<VariableGEPIndex> &VarIndices, uint64_t V1Size,
1725 uint64_t V2Size, int64_t BaseOffset, AssumptionCache *AC,
1726 DominatorTree *DT) {
1727 if (VarIndices.size() != 2 || V1Size == MemoryLocation::UnknownSize ||
1728 V2Size == MemoryLocation::UnknownSize)
1731 const VariableGEPIndex &Var0 = VarIndices[0], &Var1 = VarIndices[1];
1733 if (Var0.ZExtBits != Var1.ZExtBits || Var0.SExtBits != Var1.SExtBits ||
1734 Var0.Scale != -Var1.Scale)
1737 unsigned Width = Var1.V->getType()->getIntegerBitWidth();
1739 // We'll strip off the Extensions of Var0 and Var1 and do another round
1740 // of GetLinearExpression decomposition. In the example above, if Var0
1741 // is zext(%x + 1) we should get V1 == %x and V1Offset == 1.
1743 APInt V0Scale(Width, 0), V0Offset(Width, 0), V1Scale(Width, 0),
1745 bool NSW = true, NUW = true;
1746 unsigned V0ZExtBits = 0, V0SExtBits = 0, V1ZExtBits = 0, V1SExtBits = 0;
1747 const Value *V0 = GetLinearExpression(Var0.V, V0Scale, V0Offset, V0ZExtBits,
1748 V0SExtBits, DL, 0, AC, DT, NSW, NUW);
1751 const Value *V1 = GetLinearExpression(Var1.V, V1Scale, V1Offset, V1ZExtBits,
1752 V1SExtBits, DL, 0, AC, DT, NSW, NUW);
1754 if (V0Scale != V1Scale || V0ZExtBits != V1ZExtBits ||
1755 V0SExtBits != V1SExtBits || !isValueEqualInPotentialCycles(V0, V1))
1758 // We have a hit - Var0 and Var1 only differ by a constant offset!
1760 // If we've been sext'ed then zext'd the maximum difference between Var0 and
1761 // Var1 is possible to calculate, but we're just interested in the absolute
1762 // minimum difference between the two. The minimum distance may occur due to
1763 // wrapping; consider "add i3 %i, 5": if %i == 7 then 7 + 5 mod 8 == 4, and so
1764 // the minimum distance between %i and %i + 5 is 3.
1765 APInt MinDiff = V0Offset - V1Offset, Wrapped = -MinDiff;
1766 MinDiff = APIntOps::umin(MinDiff, Wrapped);
1767 uint64_t MinDiffBytes = MinDiff.getZExtValue() * std::abs(Var0.Scale);
1769 // We can't definitely say whether GEP1 is before or after V2 due to wrapping
1770 // arithmetic (i.e. for some values of GEP1 and V2 GEP1 < V2, and for other
1771 // values GEP1 > V2). We'll therefore only declare NoAlias if both V1Size and
1772 // V2Size can fit in the MinDiffBytes gap.
1773 return V1Size + std::abs(BaseOffset) <= MinDiffBytes &&
1774 V2Size + std::abs(BaseOffset) <= MinDiffBytes;
1777 //===----------------------------------------------------------------------===//
1778 // BasicAliasAnalysis Pass
1779 //===----------------------------------------------------------------------===//
1781 AnalysisKey BasicAA::Key;
1783 BasicAAResult BasicAA::run(Function &F, FunctionAnalysisManager &AM) {
1784 return BasicAAResult(F.getParent()->getDataLayout(),
1785 AM.getResult<TargetLibraryAnalysis>(F),
1786 AM.getResult<AssumptionAnalysis>(F),
1787 &AM.getResult<DominatorTreeAnalysis>(F),
1788 AM.getCachedResult<LoopAnalysis>(F));
1791 BasicAAWrapperPass::BasicAAWrapperPass() : FunctionPass(ID) {
1792 initializeBasicAAWrapperPassPass(*PassRegistry::getPassRegistry());
1795 char BasicAAWrapperPass::ID = 0;
1796 void BasicAAWrapperPass::anchor() {}
1798 INITIALIZE_PASS_BEGIN(BasicAAWrapperPass, "basicaa",
1799 "Basic Alias Analysis (stateless AA impl)", true, true)
1800 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
1801 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1802 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
1803 INITIALIZE_PASS_END(BasicAAWrapperPass, "basicaa",
1804 "Basic Alias Analysis (stateless AA impl)", true, true)
1806 FunctionPass *llvm::createBasicAAWrapperPass() {
1807 return new BasicAAWrapperPass();
1810 bool BasicAAWrapperPass::runOnFunction(Function &F) {
1811 auto &ACT = getAnalysis<AssumptionCacheTracker>();
1812 auto &TLIWP = getAnalysis<TargetLibraryInfoWrapperPass>();
1813 auto &DTWP = getAnalysis<DominatorTreeWrapperPass>();
1814 auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
1816 Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), TLIWP.getTLI(),
1817 ACT.getAssumptionCache(F), &DTWP.getDomTree(),
1818 LIWP ? &LIWP->getLoopInfo() : nullptr));
1823 void BasicAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
1824 AU.setPreservesAll();
1825 AU.addRequired<AssumptionCacheTracker>();
1826 AU.addRequired<DominatorTreeWrapperPass>();
1827 AU.addRequired<TargetLibraryInfoWrapperPass>();
1830 BasicAAResult llvm::createLegacyPMBasicAAResult(Pass &P, Function &F) {
1831 return BasicAAResult(
1832 F.getParent()->getDataLayout(),
1833 P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
1834 P.getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F));