//===- AliasAnalysis.cpp - Generic Alias Analysis Interface Implementation -==//
-//
+//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
//===----------------------------------------------------------------------===//
//
// This file implements the generic AliasAnalysis interface which is used as the
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Pass.h"
#include "llvm/BasicBlock.h"
-#include "llvm/iMemory.h"
+#include "llvm/Function.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Instructions.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Type.h"
#include "llvm/Target/TargetData.h"
using namespace llvm;
// Register the AliasAnalysis interface, providing a nice name to refer to.
-namespace {
- RegisterAnalysisGroup<AliasAnalysis> Z("Alias Analysis");
-}
+INITIALIZE_ANALYSIS_GROUP(AliasAnalysis, "Alias Analysis", NoAA)
+char AliasAnalysis::ID = 0;
//===----------------------------------------------------------------------===//
// Default chaining methods
//===----------------------------------------------------------------------===//
AliasAnalysis::AliasResult
-AliasAnalysis::alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
+AliasAnalysis::alias(const Location &LocA, const Location &LocB) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->alias(V1, V1Size, V2, V2Size);
+ return AA->alias(LocA, LocB);
}
-void AliasAnalysis::getMustAliases(Value *P, std::vector<Value*> &RetVals) {
+bool AliasAnalysis::pointsToConstantMemory(const Location &Loc,
+ bool OrLocal) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->getMustAliases(P, RetVals);
+ return AA->pointsToConstantMemory(Loc, OrLocal);
}
-bool AliasAnalysis::pointsToConstantMemory(const Value *P) {
+void AliasAnalysis::deleteValue(Value *V) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->pointsToConstantMemory(P);
+ AA->deleteValue(V);
}
-bool AliasAnalysis::doesNotAccessMemory(Function *F) {
+void AliasAnalysis::copyValue(Value *From, Value *To) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->doesNotAccessMemory(F);
+ AA->copyValue(From, To);
}
-bool AliasAnalysis::onlyReadsMemory(Function *F) {
+void AliasAnalysis::addEscapingUse(Use &U) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return doesNotAccessMemory(F) || AA->onlyReadsMemory(F);
+ AA->addEscapingUse(U);
}
-bool AliasAnalysis::hasNoModRefInfoForCalls() const {
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
+ const Location &Loc) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->hasNoModRefInfoForCalls();
+
+ ModRefBehavior MRB = getModRefBehavior(CS);
+ if (MRB == DoesNotAccessMemory)
+ return NoModRef;
+
+ ModRefResult Mask = ModRef;
+ if (onlyReadsMemory(MRB))
+ Mask = Ref;
+
+ if (onlyAccessesArgPointees(MRB)) {
+ bool doesAlias = false;
+ if (doesAccessArgPointees(MRB)) {
+ MDNode *CSTag = CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa);
+ for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ AI != AE; ++AI) {
+ const Value *Arg = *AI;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ Location CSLoc(Arg, UnknownSize, CSTag);
+ if (!isNoAlias(CSLoc, Loc)) {
+ doesAlias = true;
+ break;
+ }
+ }
+ }
+ if (!doesAlias)
+ return NoModRef;
+ }
+
+ // If Loc is a constant memory location, the call definitely could not
+ // modify the memory location.
+ if ((Mask & Mod) && pointsToConstantMemory(Loc))
+ Mask = ModRefResult(Mask & ~Mod);
+
+ // If this is the end of the chain, don't forward.
+ if (!AA) return Mask;
+
+ // Otherwise, fall back to the next AA in the chain. But we can merge
+ // in any mask we've managed to compute.
+ return ModRefResult(AA->getModRefInfo(CS, Loc) & Mask);
}
-void AliasAnalysis::deleteValue(Value *V) {
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- AA->deleteValue(V);
+
+ // If CS1 or CS2 are readnone, they don't interact.
+ ModRefBehavior CS1B = getModRefBehavior(CS1);
+ if (CS1B == DoesNotAccessMemory) return NoModRef;
+
+ ModRefBehavior CS2B = getModRefBehavior(CS2);
+ if (CS2B == DoesNotAccessMemory) return NoModRef;
+
+ // If they both only read from memory, there is no dependence.
+ if (onlyReadsMemory(CS1B) && onlyReadsMemory(CS2B))
+ return NoModRef;
+
+ AliasAnalysis::ModRefResult Mask = ModRef;
+
+ // If CS1 only reads memory, the only dependence on CS2 can be
+ // from CS1 reading memory written by CS2.
+ if (onlyReadsMemory(CS1B))
+ Mask = ModRefResult(Mask & Ref);
+
+ // If CS2 only access memory through arguments, accumulate the mod/ref
+ // information from CS1's references to the memory referenced by
+ // CS2's arguments.
+ if (onlyAccessesArgPointees(CS2B)) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ if (doesAccessArgPointees(CS2B)) {
+ MDNode *CS2Tag = CS2.getInstruction()->getMetadata(LLVMContext::MD_tbaa);
+ for (ImmutableCallSite::arg_iterator
+ I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
+ const Value *Arg = *I;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ Location CS2Loc(Arg, UnknownSize, CS2Tag);
+ R = ModRefResult((R | getModRefInfo(CS1, CS2Loc)) & Mask);
+ if (R == Mask)
+ break;
+ }
+ }
+ return R;
+ }
+
+ // If CS1 only accesses memory through arguments, check if CS2 references
+ // any of the memory referenced by CS1's arguments. If not, return NoModRef.
+ if (onlyAccessesArgPointees(CS1B)) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ if (doesAccessArgPointees(CS1B)) {
+ MDNode *CS1Tag = CS1.getInstruction()->getMetadata(LLVMContext::MD_tbaa);
+ for (ImmutableCallSite::arg_iterator
+ I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) {
+ const Value *Arg = *I;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ Location CS1Loc(Arg, UnknownSize, CS1Tag);
+ if (getModRefInfo(CS2, CS1Loc) != NoModRef) {
+ R = Mask;
+ break;
+ }
+ }
+ }
+ if (R == NoModRef)
+ return R;
+ }
+
+ // If this is the end of the chain, don't forward.
+ if (!AA) return Mask;
+
+ // Otherwise, fall back to the next AA in the chain. But we can merge
+ // in any mask we've managed to compute.
+ return ModRefResult(AA->getModRefInfo(CS1, CS2) & Mask);
}
-void AliasAnalysis::copyValue(Value *From, Value *To) {
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- AA->copyValue(From, To);
+
+ ModRefBehavior Min = UnknownModRefBehavior;
+
+ // Call back into the alias analysis with the other form of getModRefBehavior
+ // to see if it can give a better response.
+ if (const Function *F = CS.getCalledFunction())
+ Min = getModRefBehavior(F);
+
+ // If this is the end of the chain, don't forward.
+ if (!AA) return Min;
+
+ // Otherwise, fall back to the next AA in the chain. But we can merge
+ // in any result we've managed to compute.
+ return ModRefBehavior(AA->getModRefBehavior(CS) & Min);
}
-AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
- // FIXME: we can do better.
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(const Function *F) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->getModRefInfo(CS1, CS2);
+ return AA->getModRefBehavior(F);
}
-
//===----------------------------------------------------------------------===//
// AliasAnalysis non-virtual helper method implementation
//===----------------------------------------------------------------------===//
+AliasAnalysis::Location AliasAnalysis::getLocation(const LoadInst *LI) {
+ return Location(LI->getPointerOperand(),
+ getTypeStoreSize(LI->getType()),
+ LI->getMetadata(LLVMContext::MD_tbaa));
+}
+
+AliasAnalysis::Location AliasAnalysis::getLocation(const StoreInst *SI) {
+ return Location(SI->getPointerOperand(),
+ getTypeStoreSize(SI->getValueOperand()->getType()),
+ SI->getMetadata(LLVMContext::MD_tbaa));
+}
+
+AliasAnalysis::Location AliasAnalysis::getLocation(const VAArgInst *VI) {
+ return Location(VI->getPointerOperand(),
+ UnknownSize,
+ VI->getMetadata(LLVMContext::MD_tbaa));
+}
+
+AliasAnalysis::Location
+AliasAnalysis::getLocation(const AtomicCmpXchgInst *CXI) {
+ return Location(CXI->getPointerOperand(),
+ getTypeStoreSize(CXI->getCompareOperand()->getType()),
+ CXI->getMetadata(LLVMContext::MD_tbaa));
+}
+
+AliasAnalysis::Location
+AliasAnalysis::getLocation(const AtomicRMWInst *RMWI) {
+ return Location(RMWI->getPointerOperand(),
+ getTypeStoreSize(RMWI->getValOperand()->getType()),
+ RMWI->getMetadata(LLVMContext::MD_tbaa));
+}
+
+AliasAnalysis::Location
+AliasAnalysis::getLocationForSource(const MemTransferInst *MTI) {
+ uint64_t Size = UnknownSize;
+ if (ConstantInt *C = dyn_cast<ConstantInt>(MTI->getLength()))
+ Size = C->getValue().getZExtValue();
+
+ // memcpy/memmove can have TBAA tags. For memcpy, they apply
+ // to both the source and the destination.
+ MDNode *TBAATag = MTI->getMetadata(LLVMContext::MD_tbaa);
+
+ return Location(MTI->getRawSource(), Size, TBAATag);
+}
+
+AliasAnalysis::Location
+AliasAnalysis::getLocationForDest(const MemIntrinsic *MTI) {
+ uint64_t Size = UnknownSize;
+ if (ConstantInt *C = dyn_cast<ConstantInt>(MTI->getLength()))
+ Size = C->getValue().getZExtValue();
+
+ // memcpy/memmove can have TBAA tags. For memcpy, they apply
+ // to both the source and the destination.
+ MDNode *TBAATag = MTI->getMetadata(LLVMContext::MD_tbaa);
+
+ return Location(MTI->getRawDest(), Size, TBAATag);
+}
+
+
+
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(LoadInst *L, Value *P, unsigned Size) {
- return alias(L->getOperand(0), TD->getTypeSize(L->getType()),
- P, Size) ? Ref : NoModRef;
+AliasAnalysis::getModRefInfo(const LoadInst *L, const Location &Loc) {
+ // Be conservative in the face of volatile/atomic.
+ if (!L->isUnordered())
+ return ModRef;
+
+ // If the load address doesn't alias the given address, it doesn't read
+ // or write the specified memory.
+ if (!alias(getLocation(L), Loc))
+ return NoModRef;
+
+ // Otherwise, a load just reads.
+ return Ref;
}
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(StoreInst *S, Value *P, unsigned Size) {
- // If the stored address cannot alias the pointer in question, then the
- // pointer cannot be modified by the store.
- if (!alias(S->getOperand(1), TD->getTypeSize(S->getOperand(0)->getType()),
- P, Size))
+AliasAnalysis::getModRefInfo(const StoreInst *S, const Location &Loc) {
+ // Be conservative in the face of volatile/atomic.
+ if (!S->isUnordered())
+ return ModRef;
+
+ // If the store address cannot alias the pointer in question, then the
+ // specified memory cannot be modified by the store.
+ if (!alias(getLocation(S), Loc))
return NoModRef;
// If the pointer is a pointer to constant memory, then it could not have been
// modified by this store.
- return pointsToConstantMemory(P) ? NoModRef : Mod;
+ if (pointsToConstantMemory(Loc))
+ return NoModRef;
+
+ // Otherwise, a store just writes.
+ return Mod;
}
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
- ModRefResult Mask = ModRef;
- if (Function *F = CS.getCalledFunction())
- if (onlyReadsMemory(F)) {
- if (doesNotAccessMemory(F)) return NoModRef;
- Mask = Ref;
- }
+AliasAnalysis::getModRefInfo(const VAArgInst *V, const Location &Loc) {
+ // If the va_arg address cannot alias the pointer in question, then the
+ // specified memory cannot be accessed by the va_arg.
+ if (!alias(getLocation(V), Loc))
+ return NoModRef;
- if (!AA) return Mask;
+ // If the pointer is a pointer to constant memory, then it could not have been
+ // modified by this va_arg.
+ if (pointsToConstantMemory(Loc))
+ return NoModRef;
- // If P points to a constant memory location, the call definitely could not
- // modify the memory location.
- if ((Mask & Mod) && AA->pointsToConstantMemory(P))
- Mask = Ref;
+ // Otherwise, a va_arg reads and writes.
+ return ModRef;
+}
- return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(const AtomicCmpXchgInst *CX, const Location &Loc) {
+ // Acquire/Release cmpxchg has properties that matter for arbitrary addresses.
+ if (CX->getOrdering() > Monotonic)
+ return ModRef;
+
+ // If the cmpxchg address does not alias the location, it does not access it.
+ if (!alias(getLocation(CX), Loc))
+ return NoModRef;
+
+ return ModRef;
}
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(const AtomicRMWInst *RMW, const Location &Loc) {
+ // Acquire/Release atomicrmw has properties that matter for arbitrary addresses.
+ if (RMW->getOrdering() > Monotonic)
+ return ModRef;
+
+ // If the atomicrmw address does not alias the location, it does not access it.
+ if (!alias(getLocation(RMW), Loc))
+ return NoModRef;
+
+ return ModRef;
+}
+
+
// AliasAnalysis destructor: DO NOT move this to the header file for
// AliasAnalysis or else clients of the AliasAnalysis class may not depend on
// the AliasAnalysis.o file in the current .a file, causing alias analysis
//
AliasAnalysis::~AliasAnalysis() {}
-/// setTargetData - Subclasses must call this method to initialize the
+/// InitializeAliasAnalysis - Subclasses must call this method to initialize the
/// AliasAnalysis interface before any other methods are called.
///
void AliasAnalysis::InitializeAliasAnalysis(Pass *P) {
- TD = &P->getAnalysis<TargetData>();
+ TD = P->getAnalysisIfAvailable<TargetData>();
AA = &P->getAnalysis<AliasAnalysis>();
}
// getAnalysisUsage - All alias analysis implementations should invoke this
-// directly (using AliasAnalysis::getAnalysisUsage(AU)) to make sure that
-// TargetData is required by the pass.
+// directly (using AliasAnalysis::getAnalysisUsage(AU)).
void AliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<TargetData>(); // All AA's need TargetData.
AU.addRequired<AliasAnalysis>(); // All AA's chain
}
+/// getTypeStoreSize - Return the TargetData store size for the given type,
+/// if known, or a conservative value otherwise.
+///
+uint64_t AliasAnalysis::getTypeStoreSize(Type *Ty) {
+ return TD ? TD->getTypeStoreSize(Ty) : UnknownSize;
+}
+
/// canBasicBlockModify - Return true if it is possible for execution of the
/// specified basic block to modify the value pointed to by Ptr.
///
bool AliasAnalysis::canBasicBlockModify(const BasicBlock &BB,
- const Value *Ptr, unsigned Size) {
- return canInstructionRangeModify(BB.front(), BB.back(), Ptr, Size);
+ const Location &Loc) {
+ return canInstructionRangeModify(BB.front(), BB.back(), Loc);
}
/// canInstructionRangeModify - Return true if it is possible for the execution
///
bool AliasAnalysis::canInstructionRangeModify(const Instruction &I1,
const Instruction &I2,
- const Value *Ptr, unsigned Size) {
+ const Location &Loc) {
assert(I1.getParent() == I2.getParent() &&
"Instructions not in same basic block!");
- BasicBlock::iterator I = const_cast<Instruction*>(&I1);
- BasicBlock::iterator E = const_cast<Instruction*>(&I2);
+ BasicBlock::const_iterator I = &I1;
+ BasicBlock::const_iterator E = &I2;
++E; // Convert from inclusive to exclusive range.
for (; I != E; ++I) // Check every instruction in range
- if (getModRefInfo(I, const_cast<Value*>(Ptr), Size) & Mod)
+ if (getModRefInfo(I, Loc) & Mod)
return true;
return false;
}
-// Because of the way .a files work, we must force the BasicAA implementation to
-// be pulled in if the AliasAnalysis classes are pulled in. Otherwise we run
-// the risk of AliasAnalysis being used, but the default implementation not
-// being linked into the tool that uses it.
-//
-extern void llvm::BasicAAStub();
-static IncludeFile INCLUDE_BASICAA_CPP((void*)&BasicAAStub);
+/// isNoAliasCall - Return true if this pointer is returned by a noalias
+/// function.
+bool llvm::isNoAliasCall(const Value *V) {
+ if (isa<CallInst>(V) || isa<InvokeInst>(V))
+ return ImmutableCallSite(cast<Instruction>(V))
+ .paramHasAttr(0, Attribute::NoAlias);
+ return false;
+}
+
+/// isIdentifiedObject - Return true if this pointer refers to a distinct and
+/// identifiable object. This returns true for:
+/// Global Variables and Functions (but not Global Aliases)
+/// Allocas and Mallocs
+/// ByVal and NoAlias Arguments
+/// NoAlias returns
+///
+bool llvm::isIdentifiedObject(const Value *V) {
+ if (isa<AllocaInst>(V))
+ return true;
+ if (isa<GlobalValue>(V) && !isa<GlobalAlias>(V))
+ return true;
+ if (isNoAliasCall(V))
+ return true;
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->hasNoAliasAttr() || A->hasByValAttr();
+ return false;
+}
+
+/// isKnownNonNull - Return true if we know that the specified value is never
+/// null.
+bool llvm::isKnownNonNull(const Value *V) {
+ // Alloca never returns null, malloc might.
+ if (isa<AllocaInst>(V)) return true;
+
+ // A byval argument is never null.
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->hasByValAttr();
+
+ // Global values are not null unless extern weak.
+ if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
+ return !GV->hasExternalWeakLinkage();
+ return false;
+}
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