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/Passes.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/Analysis/AliasAnalysis.h"
20 #include "llvm/Analysis/CaptureTracking.h"
21 #include "llvm/Analysis/InstructionSimplify.h"
22 #include "llvm/Analysis/MemoryBuiltins.h"
23 #include "llvm/Analysis/ValueTracking.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/DerivedTypes.h"
27 #include "llvm/IR/Function.h"
28 #include "llvm/IR/GlobalAlias.h"
29 #include "llvm/IR/GlobalVariable.h"
30 #include "llvm/IR/Instructions.h"
31 #include "llvm/IR/IntrinsicInst.h"
32 #include "llvm/IR/LLVMContext.h"
33 #include "llvm/IR/Operator.h"
34 #include "llvm/Pass.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/GetElementPtrTypeIterator.h"
37 #include "llvm/Target/TargetLibraryInfo.h"
41 //===----------------------------------------------------------------------===//
43 //===----------------------------------------------------------------------===//
45 /// isNonEscapingLocalObject - Return true if the pointer is to a function-local
46 /// object that never escapes from the function.
47 static bool isNonEscapingLocalObject(const Value *V) {
48 // If this is a local allocation, check to see if it escapes.
49 if (isa<AllocaInst>(V) || isNoAliasCall(V))
50 // Set StoreCaptures to True so that we can assume in our callers that the
51 // pointer is not the result of a load instruction. Currently
52 // PointerMayBeCaptured doesn't have any special analysis for the
53 // StoreCaptures=false case; if it did, our callers could be refined to be
55 return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
57 // If this is an argument that corresponds to a byval or noalias argument,
58 // then it has not escaped before entering the function. Check if it escapes
59 // inside the function.
60 if (const Argument *A = dyn_cast<Argument>(V))
61 if (A->hasByValAttr() || A->hasNoAliasAttr())
62 // Note even if the argument is marked nocapture we still need to check
63 // for copies made inside the function. The nocapture attribute only
64 // specifies that there are no copies made that outlive the function.
65 return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
70 /// isEscapeSource - Return true if the pointer is one which would have
71 /// been considered an escape by isNonEscapingLocalObject.
72 static bool isEscapeSource(const Value *V) {
73 if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
76 // The load case works because isNonEscapingLocalObject considers all
77 // stores to be escapes (it passes true for the StoreCaptures argument
78 // to PointerMayBeCaptured).
85 /// getObjectSize - Return the size of the object specified by V, or
86 /// UnknownSize if unknown.
87 static uint64_t getObjectSize(const Value *V, const DataLayout &TD,
88 const TargetLibraryInfo &TLI,
89 bool RoundToAlign = false) {
91 if (getObjectSize(V, Size, &TD, &TLI, RoundToAlign))
93 return AliasAnalysis::UnknownSize;
96 /// isObjectSmallerThan - Return true if we can prove that the object specified
97 /// by V is smaller than Size.
98 static bool isObjectSmallerThan(const Value *V, uint64_t Size,
100 const TargetLibraryInfo &TLI) {
101 // Note that the meanings of the "object" are slightly different in the
102 // following contexts:
103 // c1: llvm::getObjectSize()
104 // c2: llvm.objectsize() intrinsic
105 // c3: isObjectSmallerThan()
106 // c1 and c2 share the same meaning; however, the meaning of "object" in c3
107 // refers to the "entire object".
109 // Consider this example:
110 // char *p = (char*)malloc(100)
113 // In the context of c1 and c2, the "object" pointed by q refers to the
114 // stretch of memory of q[0:19]. So, getObjectSize(q) should return 20.
116 // However, in the context of c3, the "object" refers to the chunk of memory
117 // being allocated. So, the "object" has 100 bytes, and q points to the middle
118 // the "object". In case q is passed to isObjectSmallerThan() as the 1st
119 // parameter, before the llvm::getObjectSize() is called to get the size of
120 // entire object, we should:
121 // - either rewind the pointer q to the base-address of the object in
122 // question (in this case rewind to p), or
123 // - just give up. It is up to caller to make sure the pointer is pointing
124 // to the base address the object.
126 // We go for 2nd option for simplicity.
127 if (!isIdentifiedObject(V))
130 // This function needs to use the aligned object size because we allow
131 // reads a bit past the end given sufficient alignment.
132 uint64_t ObjectSize = getObjectSize(V, TD, TLI, /*RoundToAlign*/true);
134 return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize < Size;
137 /// isObjectSize - Return true if we can prove that the object specified
138 /// by V has size Size.
139 static bool isObjectSize(const Value *V, uint64_t Size,
140 const DataLayout &TD, const TargetLibraryInfo &TLI) {
141 uint64_t ObjectSize = getObjectSize(V, TD, TLI);
142 return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize == Size;
145 /// isIdentifiedFunctionLocal - Return true if V is umabigously identified
146 /// at the function-level. Different IdentifiedFunctionLocals can't alias.
147 /// Further, an IdentifiedFunctionLocal can not alias with any function
148 /// arguments other than itself, which is not neccessarily true for
149 /// IdentifiedObjects.
150 static bool isIdentifiedFunctionLocal(const Value *V)
152 return isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasArgument(V);
156 //===----------------------------------------------------------------------===//
157 // GetElementPtr Instruction Decomposition and Analysis
158 //===----------------------------------------------------------------------===//
167 struct VariableGEPIndex {
169 ExtensionKind Extension;
172 bool operator==(const VariableGEPIndex &Other) const {
173 return V == Other.V && Extension == Other.Extension &&
174 Scale == Other.Scale;
177 bool operator!=(const VariableGEPIndex &Other) const {
178 return !operator==(Other);
184 /// GetLinearExpression - Analyze the specified value as a linear expression:
185 /// "A*V + B", where A and B are constant integers. Return the scale and offset
186 /// values as APInts and return V as a Value*, and return whether we looked
187 /// through any sign or zero extends. The incoming Value is known to have
188 /// IntegerType and it may already be sign or zero extended.
190 /// Note that this looks through extends, so the high bits may not be
191 /// represented in the result.
192 static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
193 ExtensionKind &Extension,
194 const DataLayout &TD, unsigned Depth) {
195 assert(V->getType()->isIntegerTy() && "Not an integer value");
197 // Limit our recursion depth.
204 if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
205 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
206 switch (BOp->getOpcode()) {
208 case Instruction::Or:
209 // X|C == X+C if all the bits in C are unset in X. Otherwise we can't
211 if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), &TD))
214 case Instruction::Add:
215 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
217 Offset += RHSC->getValue();
219 case Instruction::Mul:
220 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
222 Offset *= RHSC->getValue();
223 Scale *= RHSC->getValue();
225 case Instruction::Shl:
226 V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
228 Offset <<= RHSC->getValue().getLimitedValue();
229 Scale <<= RHSC->getValue().getLimitedValue();
235 // Since GEP indices are sign extended anyway, we don't care about the high
236 // bits of a sign or zero extended value - just scales and offsets. The
237 // extensions have to be consistent though.
238 if ((isa<SExtInst>(V) && Extension != EK_ZeroExt) ||
239 (isa<ZExtInst>(V) && Extension != EK_SignExt)) {
240 Value *CastOp = cast<CastInst>(V)->getOperand(0);
241 unsigned OldWidth = Scale.getBitWidth();
242 unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
243 Scale = Scale.trunc(SmallWidth);
244 Offset = Offset.trunc(SmallWidth);
245 Extension = isa<SExtInst>(V) ? EK_SignExt : EK_ZeroExt;
247 Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension,
249 Scale = Scale.zext(OldWidth);
250 Offset = Offset.zext(OldWidth);
260 /// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
261 /// into a base pointer with a constant offset and a number of scaled symbolic
264 /// The scaled symbolic offsets (represented by pairs of a Value* and a scale in
265 /// the VarIndices vector) are Value*'s that are known to be scaled by the
266 /// specified amount, but which may have other unrepresented high bits. As such,
267 /// the gep cannot necessarily be reconstructed from its decomposed form.
269 /// When DataLayout is around, this function is capable of analyzing everything
270 /// that GetUnderlyingObject can look through. When not, it just looks
271 /// through pointer casts.
274 DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
275 SmallVectorImpl<VariableGEPIndex> &VarIndices,
276 const DataLayout *TD) {
277 // Limit recursion depth to limit compile time in crazy cases.
278 unsigned MaxLookup = 6;
282 // See if this is a bitcast or GEP.
283 const Operator *Op = dyn_cast<Operator>(V);
285 // The only non-operator case we can handle are GlobalAliases.
286 if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
287 if (!GA->mayBeOverridden()) {
288 V = GA->getAliasee();
295 if (Op->getOpcode() == Instruction::BitCast) {
296 V = Op->getOperand(0);
300 const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
302 // If it's not a GEP, hand it off to SimplifyInstruction to see if it
303 // can come up with something. This matches what GetUnderlyingObject does.
304 if (const Instruction *I = dyn_cast<Instruction>(V))
305 // TODO: Get a DominatorTree and use it here.
306 if (const Value *Simplified =
307 SimplifyInstruction(const_cast<Instruction *>(I), TD)) {
315 // Don't attempt to analyze GEPs over unsized objects.
316 if (!cast<PointerType>(GEPOp->getOperand(0)->getType())
317 ->getElementType()->isSized())
320 // If we are lacking DataLayout information, we can't compute the offets of
321 // elements computed by GEPs. However, we can handle bitcast equivalent
324 if (!GEPOp->hasAllZeroIndices())
326 V = GEPOp->getOperand(0);
330 // Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
331 gep_type_iterator GTI = gep_type_begin(GEPOp);
332 for (User::const_op_iterator I = GEPOp->op_begin()+1,
333 E = GEPOp->op_end(); I != E; ++I) {
335 // Compute the (potentially symbolic) offset in bytes for this index.
336 if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
337 // For a struct, add the member offset.
338 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
339 if (FieldNo == 0) continue;
341 BaseOffs += TD->getStructLayout(STy)->getElementOffset(FieldNo);
345 // For an array/pointer, add the element offset, explicitly scaled.
346 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
347 if (CIdx->isZero()) continue;
348 BaseOffs += TD->getTypeAllocSize(*GTI)*CIdx->getSExtValue();
352 uint64_t Scale = TD->getTypeAllocSize(*GTI);
353 ExtensionKind Extension = EK_NotExtended;
355 // If the integer type is smaller than the pointer size, it is implicitly
356 // sign extended to pointer size.
357 unsigned Width = cast<IntegerType>(Index->getType())->getBitWidth();
358 if (TD->getPointerSizeInBits() > Width)
359 Extension = EK_SignExt;
361 // Use GetLinearExpression to decompose the index into a C1*V+C2 form.
362 APInt IndexScale(Width, 0), IndexOffset(Width, 0);
363 Index = GetLinearExpression(Index, IndexScale, IndexOffset, Extension,
366 // The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale.
367 // This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.
368 BaseOffs += IndexOffset.getSExtValue()*Scale;
369 Scale *= IndexScale.getSExtValue();
372 // If we already had an occurrence of this index variable, merge this
373 // scale into it. For example, we want to handle:
374 // A[x][x] -> x*16 + x*4 -> x*20
375 // This also ensures that 'x' only appears in the index list once.
376 for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
377 if (VarIndices[i].V == Index &&
378 VarIndices[i].Extension == Extension) {
379 Scale += VarIndices[i].Scale;
380 VarIndices.erase(VarIndices.begin()+i);
385 // Make sure that we have a scale that makes sense for this target's
387 if (unsigned ShiftBits = 64-TD->getPointerSizeInBits()) {
389 Scale = (int64_t)Scale >> ShiftBits;
393 VariableGEPIndex Entry = {Index, Extension,
394 static_cast<int64_t>(Scale)};
395 VarIndices.push_back(Entry);
399 // Analyze the base pointer next.
400 V = GEPOp->getOperand(0);
401 } while (--MaxLookup);
403 // If the chain of expressions is too deep, just return early.
407 /// GetIndexDifference - Dest and Src are the variable indices from two
408 /// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
409 /// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
410 /// difference between the two pointers.
411 static void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
412 const SmallVectorImpl<VariableGEPIndex> &Src) {
413 if (Src.empty()) return;
415 for (unsigned i = 0, e = Src.size(); i != e; ++i) {
416 const Value *V = Src[i].V;
417 ExtensionKind Extension = Src[i].Extension;
418 int64_t Scale = Src[i].Scale;
420 // Find V in Dest. This is N^2, but pointer indices almost never have more
421 // than a few variable indexes.
422 for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
423 if (Dest[j].V != V || Dest[j].Extension != Extension) continue;
425 // If we found it, subtract off Scale V's from the entry in Dest. If it
426 // goes to zero, remove the entry.
427 if (Dest[j].Scale != Scale)
428 Dest[j].Scale -= Scale;
430 Dest.erase(Dest.begin()+j);
435 // If we didn't consume this entry, add it to the end of the Dest list.
437 VariableGEPIndex Entry = { V, Extension, -Scale };
438 Dest.push_back(Entry);
443 //===----------------------------------------------------------------------===//
444 // BasicAliasAnalysis Pass
445 //===----------------------------------------------------------------------===//
448 static const Function *getParent(const Value *V) {
449 if (const Instruction *inst = dyn_cast<Instruction>(V))
450 return inst->getParent()->getParent();
452 if (const Argument *arg = dyn_cast<Argument>(V))
453 return arg->getParent();
458 static bool notDifferentParent(const Value *O1, const Value *O2) {
460 const Function *F1 = getParent(O1);
461 const Function *F2 = getParent(O2);
463 return !F1 || !F2 || F1 == F2;
468 /// BasicAliasAnalysis - This is the primary alias analysis implementation.
469 struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
470 static char ID; // Class identification, replacement for typeinfo
471 BasicAliasAnalysis() : ImmutablePass(ID) {
472 initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry());
475 virtual void initializePass() {
476 InitializeAliasAnalysis(this);
479 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
480 AU.addRequired<AliasAnalysis>();
481 AU.addRequired<TargetLibraryInfo>();
484 virtual AliasResult alias(const Location &LocA,
485 const Location &LocB) {
486 assert(AliasCache.empty() && "AliasCache must be cleared after use!");
487 assert(notDifferentParent(LocA.Ptr, LocB.Ptr) &&
488 "BasicAliasAnalysis doesn't support interprocedural queries.");
489 AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.TBAATag,
490 LocB.Ptr, LocB.Size, LocB.TBAATag);
491 // AliasCache rarely has more than 1 or 2 elements, always use
492 // shrink_and_clear so it quickly returns to the inline capacity of the
493 // SmallDenseMap if it ever grows larger.
494 // FIXME: This should really be shrink_to_inline_capacity_and_clear().
495 AliasCache.shrink_and_clear();
499 virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
500 const Location &Loc);
502 virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
503 ImmutableCallSite CS2) {
504 // The AliasAnalysis base class has some smarts, lets use them.
505 return AliasAnalysis::getModRefInfo(CS1, CS2);
508 /// pointsToConstantMemory - Chase pointers until we find a (constant
510 virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
512 /// getModRefBehavior - Return the behavior when calling the given
514 virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
516 /// getModRefBehavior - Return the behavior when calling the given function.
517 /// For use when the call site is not known.
518 virtual ModRefBehavior getModRefBehavior(const Function *F);
520 /// getAdjustedAnalysisPointer - This method is used when a pass implements
521 /// an analysis interface through multiple inheritance. If needed, it
522 /// should override this to adjust the this pointer as needed for the
523 /// specified pass info.
524 virtual void *getAdjustedAnalysisPointer(const void *ID) {
525 if (ID == &AliasAnalysis::ID)
526 return (AliasAnalysis*)this;
531 // AliasCache - Track alias queries to guard against recursion.
532 typedef std::pair<Location, Location> LocPair;
533 typedef SmallDenseMap<LocPair, AliasResult, 8> AliasCacheTy;
534 AliasCacheTy AliasCache;
536 // Visited - Track instructions visited by pointsToConstantMemory.
537 SmallPtrSet<const Value*, 16> Visited;
539 // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP
540 // instruction against another.
541 AliasResult aliasGEP(const GEPOperator *V1, uint64_t V1Size,
542 const MDNode *V1TBAAInfo,
543 const Value *V2, uint64_t V2Size,
544 const MDNode *V2TBAAInfo,
545 const Value *UnderlyingV1, const Value *UnderlyingV2);
547 // aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI
548 // instruction against another.
549 AliasResult aliasPHI(const PHINode *PN, uint64_t PNSize,
550 const MDNode *PNTBAAInfo,
551 const Value *V2, uint64_t V2Size,
552 const MDNode *V2TBAAInfo);
554 /// aliasSelect - Disambiguate a Select instruction against another value.
555 AliasResult aliasSelect(const SelectInst *SI, uint64_t SISize,
556 const MDNode *SITBAAInfo,
557 const Value *V2, uint64_t V2Size,
558 const MDNode *V2TBAAInfo);
560 AliasResult aliasCheck(const Value *V1, uint64_t V1Size,
561 const MDNode *V1TBAATag,
562 const Value *V2, uint64_t V2Size,
563 const MDNode *V2TBAATag);
565 } // End of anonymous namespace
567 // Register this pass...
568 char BasicAliasAnalysis::ID = 0;
569 INITIALIZE_AG_PASS_BEGIN(BasicAliasAnalysis, AliasAnalysis, "basicaa",
570 "Basic Alias Analysis (stateless AA impl)",
572 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
573 INITIALIZE_AG_PASS_END(BasicAliasAnalysis, AliasAnalysis, "basicaa",
574 "Basic Alias Analysis (stateless AA impl)",
578 ImmutablePass *llvm::createBasicAliasAnalysisPass() {
579 return new BasicAliasAnalysis();
582 /// pointsToConstantMemory - Returns whether the given pointer value
583 /// points to memory that is local to the function, with global constants being
584 /// considered local to all functions.
586 BasicAliasAnalysis::pointsToConstantMemory(const Location &Loc, bool OrLocal) {
587 assert(Visited.empty() && "Visited must be cleared after use!");
589 unsigned MaxLookup = 8;
590 SmallVector<const Value *, 16> Worklist;
591 Worklist.push_back(Loc.Ptr);
593 const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), TD);
594 if (!Visited.insert(V)) {
596 return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
599 // An alloca instruction defines local memory.
600 if (OrLocal && isa<AllocaInst>(V))
603 // A global constant counts as local memory for our purposes.
604 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
605 // Note: this doesn't require GV to be "ODR" because it isn't legal for a
606 // global to be marked constant in some modules and non-constant in
607 // others. GV may even be a declaration, not a definition.
608 if (!GV->isConstant()) {
610 return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
615 // If both select values point to local memory, then so does the select.
616 if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
617 Worklist.push_back(SI->getTrueValue());
618 Worklist.push_back(SI->getFalseValue());
622 // If all values incoming to a phi node point to local memory, then so does
624 if (const PHINode *PN = dyn_cast<PHINode>(V)) {
625 // Don't bother inspecting phi nodes with many operands.
626 if (PN->getNumIncomingValues() > MaxLookup) {
628 return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
630 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
631 Worklist.push_back(PN->getIncomingValue(i));
635 // Otherwise be conservative.
637 return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
639 } while (!Worklist.empty() && --MaxLookup);
642 return Worklist.empty();
645 /// getModRefBehavior - Return the behavior when calling the given call site.
646 AliasAnalysis::ModRefBehavior
647 BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
648 if (CS.doesNotAccessMemory())
649 // Can't do better than this.
650 return DoesNotAccessMemory;
652 ModRefBehavior Min = UnknownModRefBehavior;
654 // If the callsite knows it only reads memory, don't return worse
656 if (CS.onlyReadsMemory())
657 Min = OnlyReadsMemory;
659 // The AliasAnalysis base class has some smarts, lets use them.
660 return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
663 /// getModRefBehavior - Return the behavior when calling the given function.
664 /// For use when the call site is not known.
665 AliasAnalysis::ModRefBehavior
666 BasicAliasAnalysis::getModRefBehavior(const Function *F) {
667 // If the function declares it doesn't access memory, we can't do better.
668 if (F->doesNotAccessMemory())
669 return DoesNotAccessMemory;
671 // For intrinsics, we can check the table.
672 if (unsigned iid = F->getIntrinsicID()) {
673 #define GET_INTRINSIC_MODREF_BEHAVIOR
674 #include "llvm/IR/Intrinsics.gen"
675 #undef GET_INTRINSIC_MODREF_BEHAVIOR
678 ModRefBehavior Min = UnknownModRefBehavior;
680 // If the function declares it only reads memory, go with that.
681 if (F->onlyReadsMemory())
682 Min = OnlyReadsMemory;
684 // Otherwise be conservative.
685 return ModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min);
688 /// getModRefInfo - Check to see if the specified callsite can clobber the
689 /// specified memory object. Since we only look at local properties of this
690 /// function, we really can't say much about this query. We do, however, use
691 /// simple "address taken" analysis on local objects.
692 AliasAnalysis::ModRefResult
693 BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
694 const Location &Loc) {
695 assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
696 "AliasAnalysis query involving multiple functions!");
698 const Value *Object = GetUnderlyingObject(Loc.Ptr, TD);
700 // If this is a tail call and Loc.Ptr points to a stack location, we know that
701 // the tail call cannot access or modify the local stack.
702 // We cannot exclude byval arguments here; these belong to the caller of
703 // the current function not to the current function, and a tail callee
704 // may reference them.
705 if (isa<AllocaInst>(Object))
706 if (const CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
707 if (CI->isTailCall())
710 // If the pointer is to a locally allocated object that does not escape,
711 // then the call can not mod/ref the pointer unless the call takes the pointer
712 // as an argument, and itself doesn't capture it.
713 if (!isa<Constant>(Object) && CS.getInstruction() != Object &&
714 isNonEscapingLocalObject(Object)) {
715 bool PassedAsArg = false;
717 for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
718 CI != CE; ++CI, ++ArgNo) {
719 // Only look at the no-capture or byval pointer arguments. If this
720 // pointer were passed to arguments that were neither of these, then it
721 // couldn't be no-capture.
722 if (!(*CI)->getType()->isPointerTy() ||
723 (!CS.doesNotCapture(ArgNo) && !CS.isByValArgument(ArgNo)))
726 // If this is a no-capture pointer argument, see if we can tell that it
727 // is impossible to alias the pointer we're checking. If not, we have to
728 // assume that the call could touch the pointer, even though it doesn't
730 if (!isNoAlias(Location(*CI), Location(Object))) {
740 const TargetLibraryInfo &TLI = getAnalysis<TargetLibraryInfo>();
741 ModRefResult Min = ModRef;
743 // Finally, handle specific knowledge of intrinsics.
744 const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
746 switch (II->getIntrinsicID()) {
748 case Intrinsic::memcpy:
749 case Intrinsic::memmove: {
750 uint64_t Len = UnknownSize;
751 if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
752 Len = LenCI->getZExtValue();
753 Value *Dest = II->getArgOperand(0);
754 Value *Src = II->getArgOperand(1);
755 // If it can't overlap the source dest, then it doesn't modref the loc.
756 if (isNoAlias(Location(Dest, Len), Loc)) {
757 if (isNoAlias(Location(Src, Len), Loc))
759 // If it can't overlap the dest, then worst case it reads the loc.
761 } else if (isNoAlias(Location(Src, Len), Loc)) {
762 // If it can't overlap the source, then worst case it mutates the loc.
767 case Intrinsic::memset:
768 // Since memset is 'accesses arguments' only, the AliasAnalysis base class
769 // will handle it for the variable length case.
770 if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2))) {
771 uint64_t Len = LenCI->getZExtValue();
772 Value *Dest = II->getArgOperand(0);
773 if (isNoAlias(Location(Dest, Len), Loc))
776 // We know that memset doesn't load anything.
779 case Intrinsic::lifetime_start:
780 case Intrinsic::lifetime_end:
781 case Intrinsic::invariant_start: {
783 cast<ConstantInt>(II->getArgOperand(0))->getZExtValue();
784 if (isNoAlias(Location(II->getArgOperand(1),
786 II->getMetadata(LLVMContext::MD_tbaa)),
791 case Intrinsic::invariant_end: {
793 cast<ConstantInt>(II->getArgOperand(1))->getZExtValue();
794 if (isNoAlias(Location(II->getArgOperand(2),
796 II->getMetadata(LLVMContext::MD_tbaa)),
801 case Intrinsic::arm_neon_vld1: {
802 // LLVM's vld1 and vst1 intrinsics currently only support a single
805 TD ? TD->getTypeStoreSize(II->getType()) : UnknownSize;
806 if (isNoAlias(Location(II->getArgOperand(0), Size,
807 II->getMetadata(LLVMContext::MD_tbaa)),
812 case Intrinsic::arm_neon_vst1: {
814 TD ? TD->getTypeStoreSize(II->getArgOperand(1)->getType()) : UnknownSize;
815 if (isNoAlias(Location(II->getArgOperand(0), Size,
816 II->getMetadata(LLVMContext::MD_tbaa)),
823 // We can bound the aliasing properties of memset_pattern16 just as we can
824 // for memcpy/memset. This is particularly important because the
825 // LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
826 // whenever possible.
827 else if (TLI.has(LibFunc::memset_pattern16) &&
828 CS.getCalledFunction() &&
829 CS.getCalledFunction()->getName() == "memset_pattern16") {
830 const Function *MS = CS.getCalledFunction();
831 FunctionType *MemsetType = MS->getFunctionType();
832 if (!MemsetType->isVarArg() && MemsetType->getNumParams() == 3 &&
833 isa<PointerType>(MemsetType->getParamType(0)) &&
834 isa<PointerType>(MemsetType->getParamType(1)) &&
835 isa<IntegerType>(MemsetType->getParamType(2))) {
836 uint64_t Len = UnknownSize;
837 if (const ConstantInt *LenCI = dyn_cast<ConstantInt>(CS.getArgument(2)))
838 Len = LenCI->getZExtValue();
839 const Value *Dest = CS.getArgument(0);
840 const Value *Src = CS.getArgument(1);
841 // If it can't overlap the source dest, then it doesn't modref the loc.
842 if (isNoAlias(Location(Dest, Len), Loc)) {
843 // Always reads 16 bytes of the source.
844 if (isNoAlias(Location(Src, 16), Loc))
846 // If it can't overlap the dest, then worst case it reads the loc.
848 // Always reads 16 bytes of the source.
849 } else if (isNoAlias(Location(Src, 16), Loc)) {
850 // If it can't overlap the source, then worst case it mutates the loc.
856 // The AliasAnalysis base class has some smarts, lets use them.
857 return ModRefResult(AliasAnalysis::getModRefInfo(CS, Loc) & Min);
860 static bool areVarIndicesEqual(SmallVectorImpl<VariableGEPIndex> &Indices1,
861 SmallVectorImpl<VariableGEPIndex> &Indices2) {
862 unsigned Size1 = Indices1.size();
863 unsigned Size2 = Indices2.size();
868 for (unsigned I = 0; I != Size1; ++I)
869 if (Indices1[I] != Indices2[I])
875 /// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
876 /// against another pointer. We know that V1 is a GEP, but we don't know
877 /// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, TD),
878 /// UnderlyingV2 is the same for V2.
880 AliasAnalysis::AliasResult
881 BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
882 const MDNode *V1TBAAInfo,
883 const Value *V2, uint64_t V2Size,
884 const MDNode *V2TBAAInfo,
885 const Value *UnderlyingV1,
886 const Value *UnderlyingV2) {
887 int64_t GEP1BaseOffset;
888 SmallVector<VariableGEPIndex, 4> GEP1VariableIndices;
890 // If we have two gep instructions with must-alias or not-alias'ing base
891 // pointers, figure out if the indexes to the GEP tell us anything about the
893 if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
894 // Do the base pointers alias?
895 AliasResult BaseAlias = aliasCheck(UnderlyingV1, UnknownSize, 0,
896 UnderlyingV2, UnknownSize, 0);
898 // Check for geps of non-aliasing underlying pointers where the offsets are
900 if ((BaseAlias == MayAlias) && V1Size == V2Size) {
901 // Do the base pointers alias assuming type and size.
902 AliasResult PreciseBaseAlias = aliasCheck(UnderlyingV1, V1Size,
903 V1TBAAInfo, UnderlyingV2,
905 if (PreciseBaseAlias == NoAlias) {
906 // See if the computed offset from the common pointer tells us about the
907 // relation of the resulting pointer.
908 int64_t GEP2BaseOffset;
909 SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
910 const Value *GEP2BasePtr =
911 DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
912 const Value *GEP1BasePtr =
913 DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
914 // DecomposeGEPExpression and GetUnderlyingObject should return the
915 // same result except when DecomposeGEPExpression has no DataLayout.
916 if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
918 "DecomposeGEPExpression and GetUnderlyingObject disagree!");
922 if (GEP1BaseOffset == GEP2BaseOffset &&
923 areVarIndicesEqual(GEP1VariableIndices, GEP2VariableIndices))
925 GEP1VariableIndices.clear();
929 // If we get a No or May, then return it immediately, no amount of analysis
930 // will improve this situation.
931 if (BaseAlias != MustAlias) return BaseAlias;
933 // Otherwise, we have a MustAlias. Since the base pointers alias each other
934 // exactly, see if the computed offset from the common pointer tells us
935 // about the relation of the resulting pointer.
936 const Value *GEP1BasePtr =
937 DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
939 int64_t GEP2BaseOffset;
940 SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
941 const Value *GEP2BasePtr =
942 DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
944 // DecomposeGEPExpression and GetUnderlyingObject should return the
945 // same result except when DecomposeGEPExpression has no DataLayout.
946 if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
948 "DecomposeGEPExpression and GetUnderlyingObject disagree!");
952 // Subtract the GEP2 pointer from the GEP1 pointer to find out their
953 // symbolic difference.
954 GEP1BaseOffset -= GEP2BaseOffset;
955 GetIndexDifference(GEP1VariableIndices, GEP2VariableIndices);
958 // Check to see if these two pointers are related by the getelementptr
959 // instruction. If one pointer is a GEP with a non-zero index of the other
960 // pointer, we know they cannot alias.
962 // If both accesses are unknown size, we can't do anything useful here.
963 if (V1Size == UnknownSize && V2Size == UnknownSize)
966 AliasResult R = aliasCheck(UnderlyingV1, UnknownSize, 0,
967 V2, V2Size, V2TBAAInfo);
969 // If V2 may alias GEP base pointer, conservatively returns MayAlias.
970 // If V2 is known not to alias GEP base pointer, then the two values
971 // cannot alias per GEP semantics: "A pointer value formed from a
972 // getelementptr instruction is associated with the addresses associated
973 // with the first operand of the getelementptr".
976 const Value *GEP1BasePtr =
977 DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
979 // DecomposeGEPExpression and GetUnderlyingObject should return the
980 // same result except when DecomposeGEPExpression has no DataLayout.
981 if (GEP1BasePtr != UnderlyingV1) {
983 "DecomposeGEPExpression and GetUnderlyingObject disagree!");
988 // In the two GEP Case, if there is no difference in the offsets of the
989 // computed pointers, the resultant pointers are a must alias. This
990 // hapens when we have two lexically identical GEP's (for example).
992 // In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
993 // must aliases the GEP, the end result is a must alias also.
994 if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty())
997 // If there is a constant difference between the pointers, but the difference
998 // is less than the size of the associated memory object, then we know
999 // that the objects are partially overlapping. If the difference is
1000 // greater, we know they do not overlap.
1001 if (GEP1BaseOffset != 0 && GEP1VariableIndices.empty()) {
1002 if (GEP1BaseOffset >= 0) {
1003 if (V2Size != UnknownSize) {
1004 if ((uint64_t)GEP1BaseOffset < V2Size)
1005 return PartialAlias;
1009 if (V1Size != UnknownSize) {
1010 if (-(uint64_t)GEP1BaseOffset < V1Size)
1011 return PartialAlias;
1017 // Try to distinguish something like &A[i][1] against &A[42][0].
1018 // Grab the least significant bit set in any of the scales.
1019 if (!GEP1VariableIndices.empty()) {
1020 uint64_t Modulo = 0;
1021 for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i)
1022 Modulo |= (uint64_t)GEP1VariableIndices[i].Scale;
1023 Modulo = Modulo ^ (Modulo & (Modulo - 1));
1025 // We can compute the difference between the two addresses
1026 // mod Modulo. Check whether that difference guarantees that the
1027 // two locations do not alias.
1028 uint64_t ModOffset = (uint64_t)GEP1BaseOffset & (Modulo - 1);
1029 if (V1Size != UnknownSize && V2Size != UnknownSize &&
1030 ModOffset >= V2Size && V1Size <= Modulo - ModOffset)
1034 // Statically, we can see that the base objects are the same, but the
1035 // pointers have dynamic offsets which we can't resolve. And none of our
1036 // little tricks above worked.
1038 // TODO: Returning PartialAlias instead of MayAlias is a mild hack; the
1039 // practical effect of this is protecting TBAA in the case of dynamic
1040 // indices into arrays of unions or malloc'd memory.
1041 return PartialAlias;
1044 static AliasAnalysis::AliasResult
1045 MergeAliasResults(AliasAnalysis::AliasResult A, AliasAnalysis::AliasResult B) {
1046 // If the results agree, take it.
1049 // A mix of PartialAlias and MustAlias is PartialAlias.
1050 if ((A == AliasAnalysis::PartialAlias && B == AliasAnalysis::MustAlias) ||
1051 (B == AliasAnalysis::PartialAlias && A == AliasAnalysis::MustAlias))
1052 return AliasAnalysis::PartialAlias;
1053 // Otherwise, we don't know anything.
1054 return AliasAnalysis::MayAlias;
1057 /// aliasSelect - Provide a bunch of ad-hoc rules to disambiguate a Select
1058 /// instruction against another.
1059 AliasAnalysis::AliasResult
1060 BasicAliasAnalysis::aliasSelect(const SelectInst *SI, uint64_t SISize,
1061 const MDNode *SITBAAInfo,
1062 const Value *V2, uint64_t V2Size,
1063 const MDNode *V2TBAAInfo) {
1064 // If the values are Selects with the same condition, we can do a more precise
1065 // check: just check for aliases between the values on corresponding arms.
1066 if (const SelectInst *SI2 = dyn_cast<SelectInst>(V2))
1067 if (SI->getCondition() == SI2->getCondition()) {
1069 aliasCheck(SI->getTrueValue(), SISize, SITBAAInfo,
1070 SI2->getTrueValue(), V2Size, V2TBAAInfo);
1071 if (Alias == MayAlias)
1073 AliasResult ThisAlias =
1074 aliasCheck(SI->getFalseValue(), SISize, SITBAAInfo,
1075 SI2->getFalseValue(), V2Size, V2TBAAInfo);
1076 return MergeAliasResults(ThisAlias, Alias);
1079 // If both arms of the Select node NoAlias or MustAlias V2, then returns
1080 // NoAlias / MustAlias. Otherwise, returns MayAlias.
1082 aliasCheck(V2, V2Size, V2TBAAInfo, SI->getTrueValue(), SISize, SITBAAInfo);
1083 if (Alias == MayAlias)
1086 AliasResult ThisAlias =
1087 aliasCheck(V2, V2Size, V2TBAAInfo, SI->getFalseValue(), SISize, SITBAAInfo);
1088 return MergeAliasResults(ThisAlias, Alias);
1091 // aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI instruction
1093 AliasAnalysis::AliasResult
1094 BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
1095 const MDNode *PNTBAAInfo,
1096 const Value *V2, uint64_t V2Size,
1097 const MDNode *V2TBAAInfo) {
1098 // If the values are PHIs in the same block, we can do a more precise
1099 // as well as efficient check: just check for aliases between the values
1100 // on corresponding edges.
1101 if (const PHINode *PN2 = dyn_cast<PHINode>(V2))
1102 if (PN2->getParent() == PN->getParent()) {
1103 LocPair Locs(Location(PN, PNSize, PNTBAAInfo),
1104 Location(V2, V2Size, V2TBAAInfo));
1106 std::swap(Locs.first, Locs.second);
1107 // Analyse the PHIs' inputs under the assumption that the PHIs are
1109 // If the PHIs are May/MustAlias there must be (recursively) an input
1110 // operand from outside the PHIs' cycle that is MayAlias/MustAlias or
1111 // there must be an operation on the PHIs within the PHIs' value cycle
1112 // that causes a MayAlias.
1113 // Pretend the phis do not alias.
1114 AliasResult Alias = NoAlias;
1115 assert(AliasCache.count(Locs) &&
1116 "There must exist an entry for the phi node");
1117 AliasResult OrigAliasResult = AliasCache[Locs];
1118 AliasCache[Locs] = NoAlias;
1120 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1121 AliasResult ThisAlias =
1122 aliasCheck(PN->getIncomingValue(i), PNSize, PNTBAAInfo,
1123 PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
1124 V2Size, V2TBAAInfo);
1125 Alias = MergeAliasResults(ThisAlias, Alias);
1126 if (Alias == MayAlias)
1130 // Reset if speculation failed.
1131 if (Alias != NoAlias)
1132 AliasCache[Locs] = OrigAliasResult;
1137 SmallPtrSet<Value*, 4> UniqueSrc;
1138 SmallVector<Value*, 4> V1Srcs;
1139 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1140 Value *PV1 = PN->getIncomingValue(i);
1141 if (isa<PHINode>(PV1))
1142 // If any of the source itself is a PHI, return MayAlias conservatively
1143 // to avoid compile time explosion. The worst possible case is if both
1144 // sides are PHI nodes. In which case, this is O(m x n) time where 'm'
1145 // and 'n' are the number of PHI sources.
1147 if (UniqueSrc.insert(PV1))
1148 V1Srcs.push_back(PV1);
1151 AliasResult Alias = aliasCheck(V2, V2Size, V2TBAAInfo,
1152 V1Srcs[0], PNSize, PNTBAAInfo);
1153 // Early exit if the check of the first PHI source against V2 is MayAlias.
1154 // Other results are not possible.
1155 if (Alias == MayAlias)
1158 // If all sources of the PHI node NoAlias or MustAlias V2, then returns
1159 // NoAlias / MustAlias. Otherwise, returns MayAlias.
1160 for (unsigned i = 1, e = V1Srcs.size(); i != e; ++i) {
1161 Value *V = V1Srcs[i];
1163 AliasResult ThisAlias = aliasCheck(V2, V2Size, V2TBAAInfo,
1164 V, PNSize, PNTBAAInfo);
1165 Alias = MergeAliasResults(ThisAlias, Alias);
1166 if (Alias == MayAlias)
1173 // aliasCheck - Provide a bunch of ad-hoc rules to disambiguate in common cases,
1174 // such as array references.
1176 AliasAnalysis::AliasResult
1177 BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size,
1178 const MDNode *V1TBAAInfo,
1179 const Value *V2, uint64_t V2Size,
1180 const MDNode *V2TBAAInfo) {
1181 // If either of the memory references is empty, it doesn't matter what the
1182 // pointer values are.
1183 if (V1Size == 0 || V2Size == 0)
1186 // Strip off any casts if they exist.
1187 V1 = V1->stripPointerCasts();
1188 V2 = V2->stripPointerCasts();
1190 // Are we checking for alias of the same value?
1191 if (V1 == V2) return MustAlias;
1193 if (!V1->getType()->isPointerTy() || !V2->getType()->isPointerTy())
1194 return NoAlias; // Scalars cannot alias each other
1196 // Figure out what objects these things are pointing to if we can.
1197 const Value *O1 = GetUnderlyingObject(V1, TD);
1198 const Value *O2 = GetUnderlyingObject(V2, TD);
1200 // Null values in the default address space don't point to any object, so they
1201 // don't alias any other pointer.
1202 if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O1))
1203 if (CPN->getType()->getAddressSpace() == 0)
1205 if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O2))
1206 if (CPN->getType()->getAddressSpace() == 0)
1210 // If V1/V2 point to two different objects we know that we have no alias.
1211 if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
1214 // Constant pointers can't alias with non-const isIdentifiedObject objects.
1215 if ((isa<Constant>(O1) && isIdentifiedObject(O2) && !isa<Constant>(O2)) ||
1216 (isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
1219 // Function arguments can't alias with things that are known to be
1220 // unambigously identified at the function level.
1221 if ((isa<Argument>(O1) && isIdentifiedFunctionLocal(O2)) ||
1222 (isa<Argument>(O2) && isIdentifiedFunctionLocal(O1)))
1225 // Most objects can't alias null.
1226 if ((isa<ConstantPointerNull>(O2) && isKnownNonNull(O1)) ||
1227 (isa<ConstantPointerNull>(O1) && isKnownNonNull(O2)))
1230 // If one pointer is the result of a call/invoke or load and the other is a
1231 // non-escaping local object within the same function, then we know the
1232 // object couldn't escape to a point where the call could return it.
1234 // Note that if the pointers are in different functions, there are a
1235 // variety of complications. A call with a nocapture argument may still
1236 // temporary store the nocapture argument's value in a temporary memory
1237 // location if that memory location doesn't escape. Or it may pass a
1238 // nocapture value to other functions as long as they don't capture it.
1239 if (isEscapeSource(O1) && isNonEscapingLocalObject(O2))
1241 if (isEscapeSource(O2) && isNonEscapingLocalObject(O1))
1245 // If the size of one access is larger than the entire object on the other
1246 // side, then we know such behavior is undefined and can assume no alias.
1248 if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD, *TLI)) ||
1249 (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD, *TLI)))
1252 // Check the cache before climbing up use-def chains. This also terminates
1253 // otherwise infinitely recursive queries.
1254 LocPair Locs(Location(V1, V1Size, V1TBAAInfo),
1255 Location(V2, V2Size, V2TBAAInfo));
1257 std::swap(Locs.first, Locs.second);
1258 std::pair<AliasCacheTy::iterator, bool> Pair =
1259 AliasCache.insert(std::make_pair(Locs, MayAlias));
1261 return Pair.first->second;
1263 // FIXME: This isn't aggressively handling alias(GEP, PHI) for example: if the
1264 // GEP can't simplify, we don't even look at the PHI cases.
1265 if (!isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
1267 std::swap(V1Size, V2Size);
1269 std::swap(V1TBAAInfo, V2TBAAInfo);
1271 if (const GEPOperator *GV1 = dyn_cast<GEPOperator>(V1)) {
1272 AliasResult Result = aliasGEP(GV1, V1Size, V1TBAAInfo, V2, V2Size, V2TBAAInfo, O1, O2);
1273 if (Result != MayAlias) return AliasCache[Locs] = Result;
1276 if (isa<PHINode>(V2) && !isa<PHINode>(V1)) {
1278 std::swap(V1Size, V2Size);
1279 std::swap(V1TBAAInfo, V2TBAAInfo);
1281 if (const PHINode *PN = dyn_cast<PHINode>(V1)) {
1282 AliasResult Result = aliasPHI(PN, V1Size, V1TBAAInfo,
1283 V2, V2Size, V2TBAAInfo);
1284 if (Result != MayAlias) return AliasCache[Locs] = Result;
1287 if (isa<SelectInst>(V2) && !isa<SelectInst>(V1)) {
1289 std::swap(V1Size, V2Size);
1290 std::swap(V1TBAAInfo, V2TBAAInfo);
1292 if (const SelectInst *S1 = dyn_cast<SelectInst>(V1)) {
1293 AliasResult Result = aliasSelect(S1, V1Size, V1TBAAInfo,
1294 V2, V2Size, V2TBAAInfo);
1295 if (Result != MayAlias) return AliasCache[Locs] = Result;
1298 // If both pointers are pointing into the same object and one of them
1299 // accesses is accessing the entire object, then the accesses must
1300 // overlap in some way.
1302 if ((V1Size != UnknownSize && isObjectSize(O1, V1Size, *TD, *TLI)) ||
1303 (V2Size != UnknownSize && isObjectSize(O2, V2Size, *TD, *TLI)))
1304 return AliasCache[Locs] = PartialAlias;
1306 AliasResult Result =
1307 AliasAnalysis::alias(Location(V1, V1Size, V1TBAAInfo),
1308 Location(V2, V2Size, V2TBAAInfo));
1309 return AliasCache[Locs] = Result;