//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Type.h"
#include "llvm/Pass.h"
-#include "llvm/BasicBlock.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"
+#include "llvm/Target/TargetLibraryInfo.h"
using namespace llvm;
// Register the AliasAnalysis interface, providing a nice name to refer to.
AA->copyValue(From, To);
}
+void AliasAnalysis::addEscapingUse(Use &U) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ AA->addEscapingUse(U);
+}
+
+
AliasAnalysis::ModRefResult
AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
const Location &Loc) {
if (onlyReadsMemory(MRB))
Mask = Ref;
- if (MRB == AccessesArguments ||
- MRB == AccessesArgumentsReadonly) {
+ if (onlyAccessesArgPointees(MRB)) {
bool doesAlias = false;
- for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
- AI != AE; ++AI)
- if (!isNoAlias(Location(*AI), Loc)) {
- doesAlias = true;
- break;
+ 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 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 || CS2B == AccessesArgumentsReadonly) {
+ if (onlyAccessesArgPointees(CS2B)) {
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;
+ 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 (CS1B == AccessesArguments || CS1B == AccessesArgumentsReadonly) {
+ if (onlyAccessesArgPointees(CS1B)) {
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 (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;
}
// 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);
+ return ModRefBehavior(AA->getModRefBehavior(CS) & Min);
}
AliasAnalysis::ModRefBehavior
// 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(const LoadInst *L, const Location &Loc) {
- // Be conservative in the face of volatile.
- if (L->isVolatile())
+ // 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(Location(L->getOperand(0),
- getTypeStoreSize(L->getType()),
- L->getMetadata(LLVMContext::MD_tbaa)),
- Loc))
+ if (!alias(getLocation(L), Loc))
return NoModRef;
// Otherwise, a load just reads.
AliasAnalysis::ModRefResult
AliasAnalysis::getModRefInfo(const StoreInst *S, const Location &Loc) {
- // Be conservative in the face of volatile.
- if (S->isVolatile())
+ // 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(Location(S->getOperand(1),
- getTypeStoreSize(S->getOperand(0)->getType()),
- S->getMetadata(LLVMContext::MD_tbaa)),
- Loc))
+ if (!alias(getLocation(S), Loc))
return NoModRef;
// If the pointer is a pointer to constant memory, then it could not have been
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(Location(V->getOperand(0),
- UnknownSize,
- V->getMetadata(LLVMContext::MD_tbaa)),
- Loc))
+ if (!alias(getLocation(V), Loc))
return NoModRef;
// If the pointer is a pointer to constant memory, then it could not have been
return ModRef;
}
+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;
+}
+
+namespace {
+ /// Only find pointer captures which happen before the given instruction. Uses
+ /// the dominator tree to determine whether one instruction is before another.
+ /// Only support the case where the Value is defined in the same basic block
+ /// as the given instruction and the use.
+ struct CapturesBefore : public CaptureTracker {
+ CapturesBefore(const Instruction *I, DominatorTree *DT)
+ : BeforeHere(I), DT(DT), Captured(false) {}
+
+ void tooManyUses() { Captured = true; }
+
+ bool shouldExplore(Use *U) {
+ Instruction *I = cast<Instruction>(U->getUser());
+ BasicBlock *BB = I->getParent();
+ // We explore this usage only if the usage can reach "BeforeHere".
+ // If use is not reachable from entry, there is no need to explore.
+ if (BeforeHere != I && !DT->isReachableFromEntry(BB))
+ return false;
+ // If the value is defined in the same basic block as use and BeforeHere,
+ // there is no need to explore the use if BeforeHere dominates use.
+ // Check whether there is a path from I to BeforeHere.
+ if (BeforeHere != I && DT->dominates(BeforeHere, I) &&
+ !isPotentiallyReachable(I, BeforeHere, DT))
+ return false;
+ return true;
+ }
+
+ bool captured(Use *U) {
+ Instruction *I = cast<Instruction>(U->getUser());
+ BasicBlock *BB = I->getParent();
+ // Same logic as in shouldExplore.
+ if (BeforeHere != I && !DT->isReachableFromEntry(BB))
+ return false;
+ if (BeforeHere != I && DT->dominates(BeforeHere, I) &&
+ !isPotentiallyReachable(I, BeforeHere, DT))
+ return false;
+ Captured = true;
+ return true;
+ }
+
+ const Instruction *BeforeHere;
+ DominatorTree *DT;
+
+ bool Captured;
+ };
+}
+
+// FIXME: this is really just shoring-up a deficiency in alias analysis.
+// BasicAA isn't willing to spend linear time determining whether an alloca
+// was captured before or after this particular call, while we are. However,
+// with a smarter AA in place, this test is just wasting compile time.
+AliasAnalysis::ModRefResult
+AliasAnalysis::callCapturesBefore(const Instruction *I,
+ const AliasAnalysis::Location &MemLoc,
+ DominatorTree *DT) {
+ if (!DT || !DL) return AliasAnalysis::ModRef;
+
+ const Value *Object = GetUnderlyingObject(MemLoc.Ptr, DL);
+ if (!isIdentifiedObject(Object) || isa<GlobalValue>(Object) ||
+ isa<Constant>(Object))
+ return AliasAnalysis::ModRef;
+
+ ImmutableCallSite CS(I);
+ if (!CS.getInstruction() || CS.getInstruction() == Object)
+ return AliasAnalysis::ModRef;
+
+ CapturesBefore CB(I, DT);
+ llvm::PointerMayBeCaptured(Object, &CB);
+ if (CB.Captured)
+ return AliasAnalysis::ModRef;
+
+ unsigned ArgNo = 0;
+ AliasAnalysis::ModRefResult R = AliasAnalysis::NoModRef;
+ for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
+ CI != CE; ++CI, ++ArgNo) {
+ // Only look at the no-capture or byval pointer arguments. If this
+ // pointer were passed to arguments that were neither of these, then it
+ // couldn't be no-capture.
+ if (!(*CI)->getType()->isPointerTy() ||
+ (!CS.doesNotCapture(ArgNo) && !CS.isByValArgument(ArgNo)))
+ continue;
+
+ // If this is a no-capture pointer argument, see if we can tell that it
+ // is impossible to alias the pointer we're checking. If not, we have to
+ // assume that the call could touch the pointer, even though it doesn't
+ // escape.
+ if (isNoAlias(AliasAnalysis::Location(*CI),
+ AliasAnalysis::Location(Object)))
+ continue;
+ if (CS.doesNotAccessMemory(ArgNo))
+ continue;
+ if (CS.onlyReadsMemory(ArgNo)) {
+ R = AliasAnalysis::Ref;
+ continue;
+ }
+ return AliasAnalysis::ModRef;
+ }
+ return R;
+}
+
// 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 interface before any other methods are called.
///
void AliasAnalysis::InitializeAliasAnalysis(Pass *P) {
- TD = P->getAnalysisIfAvailable<TargetData>();
+ DataLayoutPass *DLP = P->getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : 0;
+ TLI = P->getAnalysisIfAvailable<TargetLibraryInfo>();
AA = &P->getAnalysis<AliasAnalysis>();
}
AU.addRequired<AliasAnalysis>(); // All AA's chain
}
-/// getTypeStoreSize - Return the TargetData store size for the given type,
+/// getTypeStoreSize - Return the DataLayout store size for the given type,
/// if known, or a conservative value otherwise.
///
-uint64_t AliasAnalysis::getTypeStoreSize(const Type *Ty) {
- return TD ? TD->getTypeStoreSize(Ty) : UnknownSize;
+uint64_t AliasAnalysis::getTypeStoreSize(Type *Ty) {
+ return DL ? DL->getTypeStoreSize(Ty) : UnknownSize;
}
/// canBasicBlockModify - Return true if it is possible for execution of the
return false;
}
+/// isNoAliasArgument - Return true if this is an argument with the noalias
+/// attribute.
+bool llvm::isNoAliasArgument(const Value *V)
+{
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->hasNoAliasAttr();
+ 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)
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