//===- 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/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");
+static RegisterAnalysisGroup<AliasAnalysis> Z("Alias Analysis");
+char AliasAnalysis::ID = 0;
+
+//===----------------------------------------------------------------------===//
+// Default chaining methods
+//===----------------------------------------------------------------------===//
+
+AliasAnalysis::AliasResult
+AliasAnalysis::alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->alias(V1, V1Size, V2, V2Size);
}
-AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(LoadInst *L, Value *P, unsigned Size) {
- return alias(L->getOperand(0), TD->getTypeSize(L->getType()),
- P, Size) ? Ref : NoModRef;
+bool AliasAnalysis::pointsToConstantMemory(const Value *P) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->pointsToConstantMemory(P);
+}
+
+void AliasAnalysis::deleteValue(Value *V) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ AA->deleteValue(V);
+}
+
+void AliasAnalysis::copyValue(Value *From, Value *To) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ AA->copyValue(From, To);
}
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(ImmutableCallSite CS,
+ const Value *P, unsigned Size) {
+ // Don't assert AA because BasicAA calls us in order to make use of the
+ // logic here.
+
+ ModRefBehavior MRB = getModRefBehavior(CS);
+ if (MRB == DoesNotAccessMemory)
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;
+ ModRefResult Mask = ModRef;
+ if (MRB == OnlyReadsMemory)
+ Mask = Ref;
+ else if (MRB == AliasAnalysis::AccessesArguments) {
+ bool doesAlias = false;
+ for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ AI != AE; ++AI)
+ if (!isNoAlias(*AI, ~0U, P, Size)) {
+ doesAlias = true;
+ break;
+ }
+
+ if (!doesAlias)
+ return NoModRef;
+ }
+
+ // If P points to a constant memory location, the call definitely could not
+ // modify the memory location.
+ if ((Mask & Mod) && pointsToConstantMemory(P))
+ Mask = ModRefResult(Mask & ~Mod);
+
+ // If this is BasicAA, 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, P, Size) & Mask);
}
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
- if (Function *F = CS.getCalledFunction())
- if (onlyReadsMemory(F)) {
- if (doesNotAccessMemory(F)) return NoModRef;
- return Ref;
+AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
+ // Don't assert AA because BasicAA calls us in order to make use of the
+ // logic here.
+
+ // 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 (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
+ 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 (CS1B == OnlyReadsMemory)
+ 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 (CS2B == AccessesArguments) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ for (ImmutableCallSite::arg_iterator
+ I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
+ R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
+ if (R == Mask)
+ break;
}
+ return R;
+ }
- // If P points to a constant memory location, the call definitely could not
- // modify the memory location.
- return pointsToConstantMemory(P) ? Ref : ModRef;
+ // 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 (CS1B == AccessesArguments) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ for (ImmutableCallSite::arg_iterator
+ I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
+ if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
+ R = Mask;
+ break;
+ }
+ if (R == NoModRef)
+ return R;
+ }
+
+ // If this is BasicAA, 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);
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+ // Don't assert AA because BasicAA calls us in order to make use of the
+ // logic here.
+
+ 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 BasicAA, 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 std::min(AA->getModRefBehavior(CS), Min);
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(const Function *F) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->getModRefBehavior(F);
+}
+
+AliasAnalysis::DependenceResult
+AliasAnalysis::getDependence(const Instruction *First,
+ const Value *FirstPHITranslatedAddr,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ const Value *SecondPHITranslatedAddr,
+ DependenceQueryFlags SecondFlags) {
+ assert(AA && "AA didn't call InitializeAliasAnalyais in its run method!");
+ return AA->getDependence(First, FirstPHITranslatedAddr, FirstFlags,
+ Second, SecondPHITranslatedAddr, SecondFlags);
+}
+
+//===----------------------------------------------------------------------===//
+// AliasAnalysis non-virtual helper method implementation
+//===----------------------------------------------------------------------===//
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(const LoadInst *L, const Value *P, unsigned Size) {
+ // Be conservative in the face of volatile.
+ if (L->isVolatile())
+ return ModRef;
+
+ // If the load address doesn't alias the given address, it doesn't read
+ // or write the specified memory.
+ if (!alias(L->getOperand(0), getTypeStoreSize(L->getType()), P, Size))
+ return NoModRef;
+
+ // Otherwise, a load just reads.
+ return Ref;
+}
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(const StoreInst *S, const Value *P, unsigned Size) {
+ // Be conservative in the face of volatile.
+ if (S->isVolatile())
+ return ModRef;
+
+ // If the store address cannot alias the pointer in question, then the
+ // specified memory cannot be modified by the store.
+ if (!alias(S->getOperand(1),
+ getTypeStoreSize(S->getOperand(0)->getType()), P, Size))
+ return NoModRef;
+
+ // If the pointer is a pointer to constant memory, then it could not have been
+ // modified by this store.
+ if (pointsToConstantMemory(P))
+ return NoModRef;
+
+ // Otherwise, a store just writes.
+ return Mod;
}
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
- // FIXME: could probably do better.
+AliasAnalysis::getModRefInfo(const VAArgInst *V, const Value *P, unsigned Size) {
+ // If the va_arg address cannot alias the pointer in question, then the
+ // specified memory cannot be accessed by the va_arg.
+ if (!alias(V->getOperand(0), UnknownSize, P, Size))
+ return NoModRef;
+
+ // If the pointer is a pointer to constant memory, then it could not have been
+ // modified by this va_arg.
+ if (pointsToConstantMemory(P))
+ return NoModRef;
+
+ // Otherwise, a va_arg reads and writes.
return ModRef;
}
+AliasAnalysis::DependenceResult
+AliasAnalysis::getDependenceViaModRefInfo(const Instruction *First,
+ const Value *FirstPHITranslatedAddr,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ const Value *SecondPHITranslatedAddr,
+ DependenceQueryFlags SecondFlags) {
+ if (const LoadInst *L = dyn_cast<LoadInst>(First)) {
+ // Be over-conservative with volatile for now.
+ if (L->isVolatile())
+ return Unknown;
+
+ // If we don't have a phi-translated address, use the actual one.
+ if (!FirstPHITranslatedAddr)
+ FirstPHITranslatedAddr = L->getPointerOperand();
+
+ // Forward this query to getModRefInfo.
+ switch (getModRefInfo(Second,
+ FirstPHITranslatedAddr,
+ getTypeStoreSize(L->getType()))) {
+ case NoModRef:
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ case Ref:
+ // Second only reads from the memory read from by First. If it
+ // also writes to any other memory, be conservative.
+ if (Second->mayWriteToMemory())
+ return Unknown;
+
+ // If it's loading the same size from the same address, we can
+ // give a more precise result.
+ if (const LoadInst *SecondL = dyn_cast<LoadInst>(Second)) {
+ // If we don't have a phi-translated address, use the actual one.
+ if (!SecondPHITranslatedAddr)
+ SecondPHITranslatedAddr = SecondL->getPointerOperand();
+
+ unsigned LSize = getTypeStoreSize(L->getType());
+ unsigned SecondLSize = getTypeStoreSize(SecondL->getType());
+ if (alias(FirstPHITranslatedAddr, LSize,
+ SecondPHITranslatedAddr, SecondLSize) ==
+ MustAlias) {
+ // If the loads are the same size, it's ReadThenRead.
+ if (LSize == SecondLSize)
+ return ReadThenRead;
+
+ // If the second load is smaller, it's only ReadThenReadSome.
+ if (LSize > SecondLSize)
+ return ReadThenReadSome;
+ }
+ }
+
+ // Otherwise it's just two loads.
+ return Independent;
+
+ case Mod:
+ // Second only writes to the memory read from by First. If it
+ // also reads from any other memory, be conservative.
+ if (Second->mayReadFromMemory())
+ return Unknown;
+
+ // If it's storing the same size to the same address, we can
+ // give a more precise result.
+ if (const StoreInst *SecondS = dyn_cast<StoreInst>(Second)) {
+ // If we don't have a phi-translated address, use the actual one.
+ if (!SecondPHITranslatedAddr)
+ SecondPHITranslatedAddr = SecondS->getPointerOperand();
+
+ unsigned LSize = getTypeStoreSize(L->getType());
+ unsigned SecondSSize = getTypeStoreSize(SecondS->getType());
+ if (alias(FirstPHITranslatedAddr, LSize,
+ SecondPHITranslatedAddr, SecondSSize) ==
+ MustAlias) {
+ // If the load and the store are the same size, it's ReadThenWrite.
+ if (LSize == SecondSSize)
+ return ReadThenWrite;
+ }
+ }
+
+ // Otherwise we don't know if it could be writing to other memory.
+ return Unknown;
+
+ case ModRef:
+ // Second reads and writes to the memory read from by First.
+ // We don't have a way to express that.
+ return Unknown;
+ }
+
+ } else if (const StoreInst *S = dyn_cast<StoreInst>(First)) {
+ // Be over-conservative with volatile for now.
+ if (S->isVolatile())
+ return Unknown;
+
+ // If we don't have a phi-translated address, use the actual one.
+ if (!FirstPHITranslatedAddr)
+ FirstPHITranslatedAddr = S->getPointerOperand();
+
+ // Forward this query to getModRefInfo.
+ switch (getModRefInfo(Second,
+ FirstPHITranslatedAddr,
+ getTypeStoreSize(S->getValueOperand()->getType()))) {
+ case NoModRef:
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ case Ref:
+ // Second only reads from the memory written to by First. If it
+ // also writes to any other memory, be conservative.
+ if (Second->mayWriteToMemory())
+ return Unknown;
+
+ // If it's loading the same size from the same address, we can
+ // give a more precise result.
+ if (const LoadInst *SecondL = dyn_cast<LoadInst>(Second)) {
+ // If we don't have a phi-translated address, use the actual one.
+ if (!SecondPHITranslatedAddr)
+ SecondPHITranslatedAddr = SecondL->getPointerOperand();
+
+ unsigned SSize = getTypeStoreSize(S->getValueOperand()->getType());
+ unsigned SecondLSize = getTypeStoreSize(SecondL->getType());
+ if (alias(FirstPHITranslatedAddr, SSize,
+ SecondPHITranslatedAddr, SecondLSize) ==
+ MustAlias) {
+ // If the store and the load are the same size, it's WriteThenRead.
+ if (SSize == SecondLSize)
+ return WriteThenRead;
+
+ // If the load is smaller, it's only WriteThenReadSome.
+ if (SSize > SecondLSize)
+ return WriteThenReadSome;
+ }
+ }
+
+ // Otherwise we don't know if it could be reading from other memory.
+ return Unknown;
+
+ case Mod:
+ // Second only writes to the memory written to by First. If it
+ // also reads from any other memory, be conservative.
+ if (Second->mayReadFromMemory())
+ return Unknown;
+
+ // If it's storing the same size to the same address, we can
+ // give a more precise result.
+ if (const StoreInst *SecondS = dyn_cast<StoreInst>(Second)) {
+ // If we don't have a phi-translated address, use the actual one.
+ if (!SecondPHITranslatedAddr)
+ SecondPHITranslatedAddr = SecondS->getPointerOperand();
+
+ unsigned SSize = getTypeStoreSize(S->getValueOperand()->getType());
+ unsigned SecondSSize = getTypeStoreSize(SecondS->getType());
+ if (alias(FirstPHITranslatedAddr, SSize,
+ SecondPHITranslatedAddr, SecondSSize) ==
+ MustAlias) {
+ // If the stores are the same size, it's WriteThenWrite.
+ if (SSize == SecondSSize)
+ return WriteThenWrite;
+
+ // If the second store is larger, it's only WriteSomeThenWrite.
+ if (SSize < SecondSSize)
+ return WriteSomeThenWrite;
+ }
+ }
+
+ // Otherwise we don't know if it could be writing to other memory.
+ return Unknown;
+
+ case ModRef:
+ // Second reads and writes to the memory written to by First.
+ // We don't have a way to express that.
+ return Unknown;
+ }
+
+ } else if (const VAArgInst *V = dyn_cast<VAArgInst>(First)) {
+ // If we don't have a phi-translated address, use the actual one.
+ if (!FirstPHITranslatedAddr)
+ FirstPHITranslatedAddr = V->getPointerOperand();
+
+ // Forward this query to getModRefInfo.
+ if (getModRefInfo(Second, FirstPHITranslatedAddr, UnknownSize) == NoModRef)
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ } else if (ImmutableCallSite FirstCS = cast<Value>(First)) {
+ assert(!FirstPHITranslatedAddr &&
+ !SecondPHITranslatedAddr &&
+ "PHI translation with calls not supported yet!");
+
+ // If both instructions are calls/invokes we can use the two-callsite
+ // form of getModRefInfo.
+ if (ImmutableCallSite SecondCS = cast<Value>(Second))
+ // getModRefInfo's arguments are backwards from intuition.
+ switch (getModRefInfo(SecondCS, FirstCS)) {
+ case NoModRef:
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ case Ref:
+ // If they're both read-only, there's no dependence.
+ if (FirstCS.onlyReadsMemory() && SecondCS.onlyReadsMemory())
+ return Independent;
+
+ // Otherwise it's not obvious what we can do here.
+ return Unknown;
+
+ case Mod:
+ // It's not obvious what we can do here.
+ return Unknown;
+
+ case ModRef:
+ // I know, right?
+ return Unknown;
+ }
+ }
+
+ // For anything else, be conservative.
+ return Unknown;
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getIntrinsicModRefBehavior(unsigned iid) {
+#define GET_INTRINSIC_MODREF_BEHAVIOR
+#include "llvm/Intrinsics.gen"
+#undef GET_INTRINSIC_MODREF_BEHAVIOR
+}
// AliasAnalysis destructor: DO NOT move this to the header file for
// AliasAnalysis or else clients of the AliasAnalysis class may not depend on
//
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.
+///
+unsigned AliasAnalysis::getTypeStoreSize(const Type *Ty) {
+ return TD ? TD->getTypeStoreSize(Ty) : ~0u;
}
/// canBasicBlockModify - Return true if it is possible for execution of the
const Value *Ptr, unsigned Size) {
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, Ptr, Size) & Mod)
return true;
return false;
}
+/// 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;
+}
+
// 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);
-
-
-namespace {
- struct NoAA : public ImmutablePass, public AliasAnalysis {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AliasAnalysis::getAnalysisUsage(AU);
- }
-
- virtual void initializePass() {
- InitializeAliasAnalysis(this);
- }
- };
-
- // Register this pass...
- RegisterOpt<NoAA>
- X("no-aa", "No Alias Analysis (always returns 'may' alias)");
-
- // Declare that we implement the AliasAnalysis interface
- RegisterAnalysisGroup<AliasAnalysis, NoAA> Y;
-} // End of anonymous namespace
+DEFINING_FILE_FOR(AliasAnalysis)
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