//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/TargetLibraryInfo.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/Type.h"
-#include "llvm/Target/TargetData.h"
using namespace llvm;
// Register the AliasAnalysis interface, providing a nice name to refer to.
-static 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) {
+AliasResult AliasAnalysis::alias(const MemoryLocation &LocA,
+ const MemoryLocation &LocB) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->alias(V1, V1Size, V2, V2Size);
+ return AA->alias(LocA, LocB);
}
-bool AliasAnalysis::pointsToConstantMemory(const Value *P) {
+bool AliasAnalysis::pointsToConstantMemory(const MemoryLocation &Loc,
+ bool OrLocal) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->pointsToConstantMemory(P);
+ return AA->pointsToConstantMemory(Loc, OrLocal);
+}
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getArgModRefInfo(ImmutableCallSite CS, unsigned ArgIdx) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->getArgModRefInfo(CS, ArgIdx);
}
void AliasAnalysis::deleteValue(Value *V) {
AA->deleteValue(V);
}
-void AliasAnalysis::copyValue(Value *From, Value *To) {
+void AliasAnalysis::addEscapingUse(Use &U) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ AA->addEscapingUse(U);
+}
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(Instruction *I, ImmutableCallSite Call) {
+ // We may have two calls
+ if (auto CS = ImmutableCallSite(I)) {
+ // Check if the two calls modify the same memory
+ return getModRefInfo(Call, CS);
+ } else {
+ // Otherwise, check if the call modifies or references the
+ // location this memory access defines. The best we can say
+ // is that if the call references what this instruction
+ // defines, it must be clobbered by this location.
+ const MemoryLocation DefLoc = MemoryLocation::get(I);
+ if (getModRefInfo(Call, DefLoc) != AliasAnalysis::NoModRef)
+ return AliasAnalysis::ModRef;
+ }
+ return AliasAnalysis::NoModRef;
+}
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- AA->copyValue(From, To);
+
+ ModRefBehavior MRB = getModRefBehavior(CS);
+ if (MRB == DoesNotAccessMemory)
+ return NoModRef;
+
+ ModRefResult Mask = ModRef;
+ if (onlyReadsMemory(MRB))
+ Mask = Ref;
+
+ if (onlyAccessesArgPointees(MRB)) {
+ bool doesAlias = false;
+ ModRefResult AllArgsMask = NoModRef;
+ if (doesAccessArgPointees(MRB)) {
+ for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ AI != AE; ++AI) {
+ const Value *Arg = *AI;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ unsigned ArgIdx = std::distance(CS.arg_begin(), AI);
+ MemoryLocation ArgLoc =
+ MemoryLocation::getForArgument(CS, ArgIdx, *TLI);
+ if (!isNoAlias(ArgLoc, Loc)) {
+ ModRefResult ArgMask = getArgModRefInfo(CS, ArgIdx);
+ doesAlias = true;
+ AllArgsMask = ModRefResult(AllArgsMask | ArgMask);
+ }
+ }
+ }
+ if (!doesAlias)
+ return NoModRef;
+ Mask = ModRefResult(Mask & AllArgsMask);
+ }
+
+ // 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);
}
AliasAnalysis::ModRefResult
AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
- // FIXME: we can do better.
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- return AA->getModRefInfo(CS1, CS2);
+
+ // 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)) {
+ for (ImmutableCallSite::arg_iterator
+ I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
+ const Value *Arg = *I;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ unsigned CS2ArgIdx = std::distance(CS2.arg_begin(), I);
+ auto CS2ArgLoc = MemoryLocation::getForArgument(CS2, CS2ArgIdx, *TLI);
+
+ // ArgMask indicates what CS2 might do to CS2ArgLoc, and the dependence of
+ // CS1 on that location is the inverse.
+ ModRefResult ArgMask = getArgModRefInfo(CS2, CS2ArgIdx);
+ if (ArgMask == Mod)
+ ArgMask = ModRef;
+ else if (ArgMask == Ref)
+ ArgMask = Mod;
+
+ R = ModRefResult((R | (getModRefInfo(CS1, CS2ArgLoc) & ArgMask)) & 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)) {
+ for (ImmutableCallSite::arg_iterator
+ I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) {
+ const Value *Arg = *I;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ unsigned CS1ArgIdx = std::distance(CS1.arg_begin(), I);
+ auto CS1ArgLoc = MemoryLocation::getForArgument(CS1, CS1ArgIdx, *TLI);
+
+ // ArgMask indicates what CS1 might do to CS1ArgLoc; if CS1 might Mod
+ // CS1ArgLoc, then we care about either a Mod or a Ref by CS2. If CS1
+ // might Ref, then we care only about a Mod by CS2.
+ ModRefResult ArgMask = getArgModRefInfo(CS1, CS1ArgIdx);
+ ModRefResult ArgR = getModRefInfo(CS2, CS1ArgLoc);
+ if (((ArgMask & Mod) != NoModRef && (ArgR & ModRef) != NoModRef) ||
+ ((ArgMask & Ref) != NoModRef && (ArgR & Mod) != NoModRef))
+ R = ModRefResult((R | ArgMask) & Mask);
+
+ if (R == Mask)
+ break;
+ }
+ }
+ 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);
}
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+
+ 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::ModRefBehavior
+AliasAnalysis::getModRefBehavior(const Function *F) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->getModRefBehavior(F);
+}
//===----------------------------------------------------------------------===//
// AliasAnalysis non-virtual helper method implementation
//===----------------------------------------------------------------------===//
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(const LoadInst *L, const Value *P, unsigned Size) {
+AliasAnalysis::getModRefInfo(const LoadInst *L, const MemoryLocation &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(L->getOperand(0), getTypeStoreSize(L->getType()), P, Size))
+ if (Loc.Ptr && !alias(MemoryLocation::get(L), Loc))
return NoModRef;
- // Be conservative in the face of volatile.
- if (L->isVolatile())
- return ModRef;
-
// Otherwise, a load just reads.
return Ref;
}
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(const StoreInst *S, const 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),
- getTypeStoreSize(S->getOperand(0)->getType()), P, Size))
- return NoModRef;
-
- // Be conservative in the face of volatile.
- if (S->isVolatile())
+AliasAnalysis::getModRefInfo(const StoreInst *S, const MemoryLocation &Loc) {
+ // Be conservative in the face of volatile/atomic.
+ if (!S->isUnordered())
return ModRef;
- // If the pointer is a pointer to constant memory, then it could not have been
- // modified by this store.
- if (pointsToConstantMemory(P))
- return NoModRef;
+ if (Loc.Ptr) {
+ // If the store address cannot alias the pointer in question, then the
+ // specified memory cannot be modified by the store.
+ if (!alias(MemoryLocation::get(S), Loc))
+ return NoModRef;
+
+ // If the pointer is a pointer to constant memory, then it could not have
+ // been modified by this store.
+ if (pointsToConstantMemory(Loc))
+ return NoModRef;
+
+ }
// Otherwise, a store just writes.
return Mod;
}
-AliasAnalysis::ModRefBehavior
-AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
- if (CS.doesNotAccessMemory())
- // Can't do better than this.
- return DoesNotAccessMemory;
- ModRefBehavior MRB = getModRefBehavior(CS.getCalledFunction());
- if (MRB != DoesNotAccessMemory && CS.onlyReadsMemory())
- return OnlyReadsMemory;
- return MRB;
-}
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(const VAArgInst *V, const MemoryLocation &Loc) {
-AliasAnalysis::ModRefBehavior
-AliasAnalysis::getModRefBehavior(const Function *F) {
- if (F) {
- if (F->doesNotAccessMemory())
- // Can't do better than this.
- return DoesNotAccessMemory;
- if (F->onlyReadsMemory())
- return OnlyReadsMemory;
- if (unsigned id = F->getIntrinsicID())
- return getIntrinsicModRefBehavior(id);
+ if (Loc.Ptr) {
+ // If the va_arg address cannot alias the pointer in question, then the
+ // specified memory cannot be accessed by the va_arg.
+ if (!alias(MemoryLocation::get(V), Loc))
+ return NoModRef;
+
+ // 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;
}
- return UnknownModRefBehavior;
-}
-AliasAnalysis::ModRefBehavior
-AliasAnalysis::getIntrinsicModRefBehavior(unsigned iid) {
-#define GET_INTRINSIC_MODREF_BEHAVIOR
-#include "llvm/Intrinsics.gen"
-#undef GET_INTRINSIC_MODREF_BEHAVIOR
+ // Otherwise, a va_arg reads and writes.
+ return ModRef;
}
AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
- const Value *P, unsigned Size) {
- ModRefBehavior MRB = getModRefBehavior(CS);
- if (MRB == DoesNotAccessMemory)
+AliasAnalysis::getModRefInfo(const AtomicCmpXchgInst *CX,
+ const MemoryLocation &Loc) {
+ // Acquire/Release cmpxchg has properties that matter for arbitrary addresses.
+ if (CX->getSuccessOrdering() > Monotonic)
+ return ModRef;
+
+ // If the cmpxchg address does not alias the location, it does not access it.
+ if (Loc.Ptr && !alias(MemoryLocation::get(CX), Loc))
return NoModRef;
-
- 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;
- }
+ return ModRef;
+}
- if (!AA) return Mask;
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(const AtomicRMWInst *RMW,
+ const MemoryLocation &Loc) {
+ // Acquire/Release atomicrmw has properties that matter for arbitrary addresses.
+ if (RMW->getOrdering() > Monotonic)
+ return ModRef;
- // If P points to a constant memory location, the call definitely could not
- // modify the memory location.
- if ((Mask & Mod) && AA->pointsToConstantMemory(P))
- Mask = ModRefResult(Mask & ~Mod);
+ // If the atomicrmw address does not alias the location, it does not access it.
+ if (Loc.Ptr && !alias(MemoryLocation::get(RMW), Loc))
+ return NoModRef;
- return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
+ return ModRef;
+}
+
+// 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 MemoryLocation &MemLoc, DominatorTree *DT) {
+ if (!DT)
+ 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;
+
+ if (llvm::PointerMayBeCapturedBefore(Object, /* ReturnCaptures */ true,
+ /* StoreCaptures */ true, I, DT,
+ /* include Object */ true))
+ 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(MemoryLocation(*CI), MemoryLocation(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
/// InitializeAliasAnalysis - Subclasses must call this method to initialize the
/// AliasAnalysis interface before any other methods are called.
///
-void AliasAnalysis::InitializeAliasAnalysis(Pass *P) {
- TD = P->getAnalysisIfAvailable<TargetData>();
+void AliasAnalysis::InitializeAliasAnalysis(Pass *P, const DataLayout *NewDL) {
+ DL = NewDL;
+ auto *TLIP = P->getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
+ TLI = TLIP ? &TLIP->getTLI() : nullptr;
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.
///
-unsigned AliasAnalysis::getTypeStoreSize(const Type *Ty) {
- return TD ? TD->getTypeStoreSize(Ty) : ~0u;
+uint64_t AliasAnalysis::getTypeStoreSize(Type *Ty) {
+ return DL ? DL->getTypeStoreSize(Ty) : MemoryLocation::UnknownSize;
}
/// canBasicBlockModify - Return true if it is possible for execution of the
-/// specified basic block to modify the value pointed to by Ptr.
+/// specified basic block to modify the location Loc.
///
bool AliasAnalysis::canBasicBlockModify(const BasicBlock &BB,
- const Value *Ptr, unsigned Size) {
- return canInstructionRangeModify(BB.front(), BB.back(), Ptr, Size);
+ const MemoryLocation &Loc) {
+ return canInstructionRangeModRef(BB.front(), BB.back(), Loc, Mod);
}
-/// canInstructionRangeModify - Return true if it is possible for the execution
-/// of the specified instructions to modify the value pointed to by Ptr. The
-/// instructions to consider are all of the instructions in the range of [I1,I2]
-/// INCLUSIVE. I1 and I2 must be in the same basic block.
-///
-bool AliasAnalysis::canInstructionRangeModify(const Instruction &I1,
+/// canInstructionRangeModRef - Return true if it is possible for the
+/// execution of the specified instructions to mod\ref (according to the
+/// mode) the location Loc. The instructions to consider are all
+/// of the instructions in the range of [I1,I2] INCLUSIVE.
+/// I1 and I2 must be in the same basic block.
+bool AliasAnalysis::canInstructionRangeModRef(const Instruction &I1,
const Instruction &I2,
- const Value *Ptr, unsigned Size) {
+ const MemoryLocation &Loc,
+ const ModRefResult Mode) {
assert(I1.getParent() == I2.getParent() &&
"Instructions not in same basic block!");
BasicBlock::const_iterator I = &I1;
++E; // Convert from inclusive to exclusive range.
for (; I != E; ++I) // Check every instruction in range
- if (getModRefInfo(I, Ptr, Size) & Mod)
+ if (getModRefInfo(I, Loc) & Mode)
return true;
return false;
}
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)
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.
-DEFINING_FILE_FOR(AliasAnalysis)
+/// isIdentifiedFunctionLocal - Return true if V is umabigously identified
+/// at the function-level. Different IdentifiedFunctionLocals can't alias.
+/// Further, an IdentifiedFunctionLocal can not alias with any function
+/// arguments other than itself, which is not necessarily true for
+/// IdentifiedObjects.
+bool llvm::isIdentifiedFunctionLocal(const Value *V)
+{
+ return isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasArgument(V);
+}
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