//===----------------------------------------------------------------------===//
#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);
}
-void AliasAnalysis::deleteValue(Value *V) {
+ModRefInfo AliasAnalysis::getArgModRefInfo(ImmutableCallSite CS,
+ unsigned ArgIdx) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- AA->deleteValue(V);
+ return AA->getArgModRefInfo(CS, ArgIdx);
}
-void AliasAnalysis::copyValue(Value *From, Value *To) {
+ModRefInfo 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) != MRI_NoModRef)
+ return MRI_ModRef;
+ }
+ return MRI_NoModRef;
+}
+
+ModRefInfo AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
+ const MemoryLocation &Loc) {
assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
- AA->copyValue(From, To);
+
+ auto MRB = getModRefBehavior(CS);
+ if (MRB == FMRB_DoesNotAccessMemory)
+ return MRI_NoModRef;
+
+ ModRefInfo Mask = MRI_ModRef;
+ if (onlyReadsMemory(MRB))
+ Mask = MRI_Ref;
+
+ if (onlyAccessesArgPointees(MRB)) {
+ bool doesAlias = false;
+ ModRefInfo AllArgsMask = MRI_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)) {
+ ModRefInfo ArgMask = getArgModRefInfo(CS, ArgIdx);
+ doesAlias = true;
+ AllArgsMask = ModRefInfo(AllArgsMask | ArgMask);
+ }
+ }
+ }
+ if (!doesAlias)
+ return MRI_NoModRef;
+ Mask = ModRefInfo(Mask & AllArgsMask);
+ }
+
+ // If Loc is a constant memory location, the call definitely could not
+ // modify the memory location.
+ if ((Mask & MRI_Mod) && pointsToConstantMemory(Loc))
+ Mask = ModRefInfo(Mask & ~MRI_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 ModRefInfo(AA->getModRefInfo(CS, Loc) & Mask);
}
-AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
+ModRefInfo AliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
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.
+ auto CS1B = getModRefBehavior(CS1);
+ if (CS1B == FMRB_DoesNotAccessMemory)
+ return MRI_NoModRef;
+
+ auto CS2B = getModRefBehavior(CS2);
+ if (CS2B == FMRB_DoesNotAccessMemory)
+ return MRI_NoModRef;
+
+ // If they both only read from memory, there is no dependence.
+ if (onlyReadsMemory(CS1B) && onlyReadsMemory(CS2B))
+ return MRI_NoModRef;
+
+ ModRefInfo Mask = MRI_ModRef;
+
+ // If CS1 only reads memory, the only dependence on CS2 can be
+ // from CS1 reading memory written by CS2.
+ if (onlyReadsMemory(CS1B))
+ Mask = ModRefInfo(Mask & MRI_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)) {
+ ModRefInfo R = MRI_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.
+ ModRefInfo ArgMask = getArgModRefInfo(CS2, CS2ArgIdx);
+ if (ArgMask == MRI_Mod)
+ ArgMask = MRI_ModRef;
+ else if (ArgMask == MRI_Ref)
+ ArgMask = MRI_Mod;
+
+ R = ModRefInfo((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)) {
+ ModRefInfo R = MRI_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.
+ ModRefInfo ArgMask = getArgModRefInfo(CS1, CS1ArgIdx);
+ ModRefInfo ArgR = getModRefInfo(CS2, CS1ArgLoc);
+ if (((ArgMask & MRI_Mod) != MRI_NoModRef &&
+ (ArgR & MRI_ModRef) != MRI_NoModRef) ||
+ ((ArgMask & MRI_Ref) != MRI_NoModRef &&
+ (ArgR & MRI_Mod) != MRI_NoModRef))
+ R = ModRefInfo((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 ModRefInfo(AA->getModRefInfo(CS1, CS2) & Mask);
}
+FunctionModRefBehavior AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+
+ auto Min = FMRB_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 FunctionModRefBehavior(AA->getModRefBehavior(CS) & Min);
+}
+
+FunctionModRefBehavior 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) {
+ModRefInfo AliasAnalysis::getModRefInfo(const LoadInst *L,
+ const MemoryLocation &Loc) {
+ // Be conservative in the face of volatile/atomic.
+ if (!L->isUnordered())
+ return MRI_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;
-
- // Be conservative in the face of volatile.
- if (L->isVolatile())
- return ModRef;
+ if (Loc.Ptr && !alias(MemoryLocation::get(L), Loc))
+ return MRI_NoModRef;
// Otherwise, a load just reads.
- return Ref;
+ return MRI_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())
- 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;
+ModRefInfo AliasAnalysis::getModRefInfo(const StoreInst *S,
+ const MemoryLocation &Loc) {
+ // Be conservative in the face of volatile/atomic.
+ if (!S->isUnordered())
+ return MRI_ModRef;
+
+ 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 MRI_NoModRef;
+
+ // If the pointer is a pointer to constant memory, then it could not have
+ // been modified by this store.
+ if (pointsToConstantMemory(Loc))
+ return MRI_NoModRef;
+ }
// Otherwise, a store just writes.
- return Mod;
+ return MRI_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;
-}
+ModRefInfo 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 MRI_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 MRI_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 MRI_ModRef;
}
-AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
- const Value *P, unsigned Size) {
- ModRefBehavior MRB = getModRefBehavior(CS);
- if (MRB == DoesNotAccessMemory)
- 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;
- }
+ModRefInfo AliasAnalysis::getModRefInfo(const AtomicCmpXchgInst *CX,
+ const MemoryLocation &Loc) {
+ // Acquire/Release cmpxchg has properties that matter for arbitrary addresses.
+ if (CX->getSuccessOrdering() > Monotonic)
+ return MRI_ModRef;
- if (!doesAlias)
- return NoModRef;
- }
+ // If the cmpxchg address does not alias the location, it does not access it.
+ if (Loc.Ptr && !alias(MemoryLocation::get(CX), Loc))
+ return MRI_NoModRef;
- if (!AA) return Mask;
+ return MRI_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);
+ModRefInfo AliasAnalysis::getModRefInfo(const AtomicRMWInst *RMW,
+ const MemoryLocation &Loc) {
+ // Acquire/Release atomicrmw has properties that matter for arbitrary addresses.
+ if (RMW->getOrdering() > Monotonic)
+ return MRI_ModRef;
+
+ // If the atomicrmw address does not alias the location, it does not access it.
+ if (Loc.Ptr && !alias(MemoryLocation::get(RMW), Loc))
+ return MRI_NoModRef;
+
+ return MRI_ModRef;
+}
- return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
+/// \brief Return information about whether a particular call site modifies
+/// or reads the specified memory location \p MemLoc before instruction \p I
+/// in a BasicBlock. A ordered basic block \p OBB can be used to speed up
+/// instruction-ordering queries inside the BasicBlock containing \p I.
+/// 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.
+ModRefInfo AliasAnalysis::callCapturesBefore(const Instruction *I,
+ const MemoryLocation &MemLoc,
+ DominatorTree *DT,
+ OrderedBasicBlock *OBB) {
+ if (!DT)
+ return MRI_ModRef;
+
+ const Value *Object = GetUnderlyingObject(MemLoc.Ptr, *DL);
+ if (!isIdentifiedObject(Object) || isa<GlobalValue>(Object) ||
+ isa<Constant>(Object))
+ return MRI_ModRef;
+
+ ImmutableCallSite CS(I);
+ if (!CS.getInstruction() || CS.getInstruction() == Object)
+ return MRI_ModRef;
+
+ if (llvm::PointerMayBeCapturedBefore(Object, /* ReturnCaptures */ true,
+ /* StoreCaptures */ true, I, DT,
+ /* include Object */ true,
+ /* OrderedBasicBlock */ OBB))
+ return MRI_ModRef;
+
+ unsigned ArgNo = 0;
+ ModRefInfo R = MRI_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 = MRI_Ref;
+ continue;
+ }
+ return MRI_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,
-/// 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
-/// 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, MRI_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 ModRefInfo 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;
}
/// 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);
+ if (auto CS = ImmutableCallSite(V))
+ return CS.paramHasAttr(0, Attribute::NoAlias);
+ 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;
}
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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