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Diffstat (limited to 'contrib/llvm-project/llvm/lib/Analysis/AliasAnalysis.cpp')
| -rw-r--r-- | contrib/llvm-project/llvm/lib/Analysis/AliasAnalysis.cpp | 948 |
1 files changed, 948 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Analysis/AliasAnalysis.cpp b/contrib/llvm-project/llvm/lib/Analysis/AliasAnalysis.cpp new file mode 100644 index 000000000000..9e24f6b87bdb --- /dev/null +++ b/contrib/llvm-project/llvm/lib/Analysis/AliasAnalysis.cpp @@ -0,0 +1,948 @@ +//==- AliasAnalysis.cpp - Generic Alias Analysis Interface Implementation --==// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements the generic AliasAnalysis interface which is used as the +// common interface used by all clients and implementations of alias analysis. +// +// This file also implements the default version of the AliasAnalysis interface +// that is to be used when no other implementation is specified. This does some +// simple tests that detect obvious cases: two different global pointers cannot +// alias, a global cannot alias a malloc, two different mallocs cannot alias, +// etc. +// +// This alias analysis implementation really isn't very good for anything, but +// it is very fast, and makes a nice clean default implementation. Because it +// handles lots of little corner cases, other, more complex, alias analysis +// implementations may choose to rely on this pass to resolve these simple and +// easy cases. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/BasicAliasAnalysis.h" +#include "llvm/Analysis/CaptureTracking.h" +#include "llvm/Analysis/GlobalsModRef.h" +#include "llvm/Analysis/MemoryLocation.h" +#include "llvm/Analysis/ObjCARCAliasAnalysis.h" +#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h" +#include "llvm/Analysis/ScopedNoAliasAA.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/TypeBasedAliasAnalysis.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/Argument.h" +#include "llvm/IR/Attributes.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/Instruction.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/Type.h" +#include "llvm/IR/Value.h" +#include "llvm/InitializePasses.h" +#include "llvm/Pass.h" +#include "llvm/Support/AtomicOrdering.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/CommandLine.h" +#include <algorithm> +#include <cassert> +#include <functional> +#include <iterator> + +#define DEBUG_TYPE "aa" + +using namespace llvm; + +STATISTIC(NumNoAlias, "Number of NoAlias results"); +STATISTIC(NumMayAlias, "Number of MayAlias results"); +STATISTIC(NumMustAlias, "Number of MustAlias results"); + +namespace llvm { +/// Allow disabling BasicAA from the AA results. This is particularly useful +/// when testing to isolate a single AA implementation. +cl::opt<bool> DisableBasicAA("disable-basic-aa", cl::Hidden, cl::init(false)); +} // namespace llvm + +#ifndef NDEBUG +/// Print a trace of alias analysis queries and their results. +static cl::opt<bool> EnableAATrace("aa-trace", cl::Hidden, cl::init(false)); +#else +static const bool EnableAATrace = false; +#endif + +AAResults::AAResults(AAResults &&Arg) + : TLI(Arg.TLI), AAs(std::move(Arg.AAs)), AADeps(std::move(Arg.AADeps)) {} + +AAResults::~AAResults() {} + +bool AAResults::invalidate(Function &F, const PreservedAnalyses &PA, + FunctionAnalysisManager::Invalidator &Inv) { + // AAResults preserves the AAManager by default, due to the stateless nature + // of AliasAnalysis. There is no need to check whether it has been preserved + // explicitly. Check if any module dependency was invalidated and caused the + // AAManager to be invalidated. Invalidate ourselves in that case. + auto PAC = PA.getChecker<AAManager>(); + if (!PAC.preservedWhenStateless()) + return true; + + // Check if any of the function dependencies were invalidated, and invalidate + // ourselves in that case. + for (AnalysisKey *ID : AADeps) + if (Inv.invalidate(ID, F, PA)) + return true; + + // Everything we depend on is still fine, so are we. Nothing to invalidate. + return false; +} + +//===----------------------------------------------------------------------===// +// Default chaining methods +//===----------------------------------------------------------------------===// + +AliasResult AAResults::alias(const MemoryLocation &LocA, + const MemoryLocation &LocB) { + SimpleAAQueryInfo AAQIP(*this); + return alias(LocA, LocB, AAQIP, nullptr); +} + +AliasResult AAResults::alias(const MemoryLocation &LocA, + const MemoryLocation &LocB, AAQueryInfo &AAQI, + const Instruction *CtxI) { + AliasResult Result = AliasResult::MayAlias; + + if (EnableAATrace) { + for (unsigned I = 0; I < AAQI.Depth; ++I) + dbgs() << " "; + dbgs() << "Start " << *LocA.Ptr << " @ " << LocA.Size << ", " + << *LocB.Ptr << " @ " << LocB.Size << "\n"; + } + + AAQI.Depth++; + for (const auto &AA : AAs) { + Result = AA->alias(LocA, LocB, AAQI, CtxI); + if (Result != AliasResult::MayAlias) + break; + } + AAQI.Depth--; + + if (EnableAATrace) { + for (unsigned I = 0; I < AAQI.Depth; ++I) + dbgs() << " "; + dbgs() << "End " << *LocA.Ptr << " @ " << LocA.Size << ", " + << *LocB.Ptr << " @ " << LocB.Size << " = " << Result << "\n"; + } + + if (AAQI.Depth == 0) { + if (Result == AliasResult::NoAlias) + ++NumNoAlias; + else if (Result == AliasResult::MustAlias) + ++NumMustAlias; + else + ++NumMayAlias; + } + return Result; +} + +ModRefInfo AAResults::getModRefInfoMask(const MemoryLocation &Loc, + bool IgnoreLocals) { + SimpleAAQueryInfo AAQIP(*this); + return getModRefInfoMask(Loc, AAQIP, IgnoreLocals); +} + +ModRefInfo AAResults::getModRefInfoMask(const MemoryLocation &Loc, + AAQueryInfo &AAQI, bool IgnoreLocals) { + ModRefInfo Result = ModRefInfo::ModRef; + + for (const auto &AA : AAs) { + Result &= AA->getModRefInfoMask(Loc, AAQI, IgnoreLocals); + + // Early-exit the moment we reach the bottom of the lattice. + if (isNoModRef(Result)) + return ModRefInfo::NoModRef; + } + + return Result; +} + +ModRefInfo AAResults::getArgModRefInfo(const CallBase *Call, unsigned ArgIdx) { + ModRefInfo Result = ModRefInfo::ModRef; + + for (const auto &AA : AAs) { + Result &= AA->getArgModRefInfo(Call, ArgIdx); + + // Early-exit the moment we reach the bottom of the lattice. + if (isNoModRef(Result)) + return ModRefInfo::NoModRef; + } + + return Result; +} + +ModRefInfo AAResults::getModRefInfo(const Instruction *I, + const CallBase *Call2) { + SimpleAAQueryInfo AAQIP(*this); + return getModRefInfo(I, Call2, AAQIP); +} + +ModRefInfo AAResults::getModRefInfo(const Instruction *I, const CallBase *Call2, + AAQueryInfo &AAQI) { + // We may have two calls. + if (const auto *Call1 = dyn_cast<CallBase>(I)) { + // Check if the two calls modify the same memory. + return getModRefInfo(Call1, Call2, AAQI); + } + // If this is a fence, just return ModRef. + if (I->isFenceLike()) + return ModRefInfo::ModRef; + // 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); + ModRefInfo MR = getModRefInfo(Call2, DefLoc, AAQI); + if (isModOrRefSet(MR)) + return ModRefInfo::ModRef; + return ModRefInfo::NoModRef; +} + +ModRefInfo AAResults::getModRefInfo(const CallBase *Call, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + ModRefInfo Result = ModRefInfo::ModRef; + + for (const auto &AA : AAs) { + Result &= AA->getModRefInfo(Call, Loc, AAQI); + + // Early-exit the moment we reach the bottom of the lattice. + if (isNoModRef(Result)) + return ModRefInfo::NoModRef; + } + + // Try to refine the mod-ref info further using other API entry points to the + // aggregate set of AA results. + + // We can completely ignore inaccessible memory here, because MemoryLocations + // can only reference accessible memory. + auto ME = getMemoryEffects(Call, AAQI) + .getWithoutLoc(MemoryEffects::InaccessibleMem); + if (ME.doesNotAccessMemory()) + return ModRefInfo::NoModRef; + + ModRefInfo ArgMR = ME.getModRef(MemoryEffects::ArgMem); + ModRefInfo OtherMR = ME.getWithoutLoc(MemoryEffects::ArgMem).getModRef(); + if ((ArgMR | OtherMR) != OtherMR) { + // Refine the modref info for argument memory. We only bother to do this + // if ArgMR is not a subset of OtherMR, otherwise this won't have an impact + // on the final result. + ModRefInfo AllArgsMask = ModRefInfo::NoModRef; + for (const auto &I : llvm::enumerate(Call->args())) { + const Value *Arg = I.value(); + if (!Arg->getType()->isPointerTy()) + continue; + unsigned ArgIdx = I.index(); + MemoryLocation ArgLoc = MemoryLocation::getForArgument(Call, ArgIdx, TLI); + AliasResult ArgAlias = alias(ArgLoc, Loc, AAQI, Call); + if (ArgAlias != AliasResult::NoAlias) + AllArgsMask |= getArgModRefInfo(Call, ArgIdx); + } + ArgMR &= AllArgsMask; + } + + Result &= ArgMR | OtherMR; + + // Apply the ModRef mask. This ensures that if Loc is a constant memory + // location, we take into account the fact that the call definitely could not + // modify the memory location. + if (!isNoModRef(Result)) + Result &= getModRefInfoMask(Loc); + + return Result; +} + +ModRefInfo AAResults::getModRefInfo(const CallBase *Call1, + const CallBase *Call2, AAQueryInfo &AAQI) { + ModRefInfo Result = ModRefInfo::ModRef; + + for (const auto &AA : AAs) { + Result &= AA->getModRefInfo(Call1, Call2, AAQI); + + // Early-exit the moment we reach the bottom of the lattice. + if (isNoModRef(Result)) + return ModRefInfo::NoModRef; + } + + // Try to refine the mod-ref info further using other API entry points to the + // aggregate set of AA results. + + // If Call1 or Call2 are readnone, they don't interact. + auto Call1B = getMemoryEffects(Call1, AAQI); + if (Call1B.doesNotAccessMemory()) + return ModRefInfo::NoModRef; + + auto Call2B = getMemoryEffects(Call2, AAQI); + if (Call2B.doesNotAccessMemory()) + return ModRefInfo::NoModRef; + + // If they both only read from memory, there is no dependence. + if (Call1B.onlyReadsMemory() && Call2B.onlyReadsMemory()) + return ModRefInfo::NoModRef; + + // If Call1 only reads memory, the only dependence on Call2 can be + // from Call1 reading memory written by Call2. + if (Call1B.onlyReadsMemory()) + Result &= ModRefInfo::Ref; + else if (Call1B.onlyWritesMemory()) + Result &= ModRefInfo::Mod; + + // If Call2 only access memory through arguments, accumulate the mod/ref + // information from Call1's references to the memory referenced by + // Call2's arguments. + if (Call2B.onlyAccessesArgPointees()) { + if (!Call2B.doesAccessArgPointees()) + return ModRefInfo::NoModRef; + ModRefInfo R = ModRefInfo::NoModRef; + for (auto I = Call2->arg_begin(), E = Call2->arg_end(); I != E; ++I) { + const Value *Arg = *I; + if (!Arg->getType()->isPointerTy()) + continue; + unsigned Call2ArgIdx = std::distance(Call2->arg_begin(), I); + auto Call2ArgLoc = + MemoryLocation::getForArgument(Call2, Call2ArgIdx, TLI); + + // ArgModRefC2 indicates what Call2 might do to Call2ArgLoc, and the + // dependence of Call1 on that location is the inverse: + // - If Call2 modifies location, dependence exists if Call1 reads or + // writes. + // - If Call2 only reads location, dependence exists if Call1 writes. + ModRefInfo ArgModRefC2 = getArgModRefInfo(Call2, Call2ArgIdx); + ModRefInfo ArgMask = ModRefInfo::NoModRef; + if (isModSet(ArgModRefC2)) + ArgMask = ModRefInfo::ModRef; + else if (isRefSet(ArgModRefC2)) + ArgMask = ModRefInfo::Mod; + + // ModRefC1 indicates what Call1 might do to Call2ArgLoc, and we use + // above ArgMask to update dependence info. + ArgMask &= getModRefInfo(Call1, Call2ArgLoc, AAQI); + + R = (R | ArgMask) & Result; + if (R == Result) + break; + } + + return R; + } + + // If Call1 only accesses memory through arguments, check if Call2 references + // any of the memory referenced by Call1's arguments. If not, return NoModRef. + if (Call1B.onlyAccessesArgPointees()) { + if (!Call1B.doesAccessArgPointees()) + return ModRefInfo::NoModRef; + ModRefInfo R = ModRefInfo::NoModRef; + for (auto I = Call1->arg_begin(), E = Call1->arg_end(); I != E; ++I) { + const Value *Arg = *I; + if (!Arg->getType()->isPointerTy()) + continue; + unsigned Call1ArgIdx = std::distance(Call1->arg_begin(), I); + auto Call1ArgLoc = + MemoryLocation::getForArgument(Call1, Call1ArgIdx, TLI); + + // ArgModRefC1 indicates what Call1 might do to Call1ArgLoc; if Call1 + // might Mod Call1ArgLoc, then we care about either a Mod or a Ref by + // Call2. If Call1 might Ref, then we care only about a Mod by Call2. + ModRefInfo ArgModRefC1 = getArgModRefInfo(Call1, Call1ArgIdx); + ModRefInfo ModRefC2 = getModRefInfo(Call2, Call1ArgLoc, AAQI); + if ((isModSet(ArgModRefC1) && isModOrRefSet(ModRefC2)) || + (isRefSet(ArgModRefC1) && isModSet(ModRefC2))) + R = (R | ArgModRefC1) & Result; + + if (R == Result) + break; + } + + return R; + } + + return Result; +} + +MemoryEffects AAResults::getMemoryEffects(const CallBase *Call, + AAQueryInfo &AAQI) { + MemoryEffects Result = MemoryEffects::unknown(); + + for (const auto &AA : AAs) { + Result &= AA->getMemoryEffects(Call, AAQI); + + // Early-exit the moment we reach the bottom of the lattice. + if (Result.doesNotAccessMemory()) + return Result; + } + + return Result; +} + +MemoryEffects AAResults::getMemoryEffects(const CallBase *Call) { + SimpleAAQueryInfo AAQI(*this); + return getMemoryEffects(Call, AAQI); +} + +MemoryEffects AAResults::getMemoryEffects(const Function *F) { + MemoryEffects Result = MemoryEffects::unknown(); + + for (const auto &AA : AAs) { + Result &= AA->getMemoryEffects(F); + + // Early-exit the moment we reach the bottom of the lattice. + if (Result.doesNotAccessMemory()) + return Result; + } + + return Result; +} + +raw_ostream &llvm::operator<<(raw_ostream &OS, AliasResult AR) { + switch (AR) { + case AliasResult::NoAlias: + OS << "NoAlias"; + break; + case AliasResult::MustAlias: + OS << "MustAlias"; + break; + case AliasResult::MayAlias: + OS << "MayAlias"; + break; + case AliasResult::PartialAlias: + OS << "PartialAlias"; + if (AR.hasOffset()) + OS << " (off " << AR.getOffset() << ")"; + break; + } + return OS; +} + +raw_ostream &llvm::operator<<(raw_ostream &OS, ModRefInfo MR) { + switch (MR) { + case ModRefInfo::NoModRef: + OS << "NoModRef"; + break; + case ModRefInfo::Ref: + OS << "Ref"; + break; + case ModRefInfo::Mod: + OS << "Mod"; + break; + case ModRefInfo::ModRef: + OS << "ModRef"; + break; + } + return OS; +} + +raw_ostream &llvm::operator<<(raw_ostream &OS, MemoryEffects ME) { + for (MemoryEffects::Location Loc : MemoryEffects::locations()) { + switch (Loc) { + case MemoryEffects::ArgMem: + OS << "ArgMem: "; + break; + case MemoryEffects::InaccessibleMem: + OS << "InaccessibleMem: "; + break; + case MemoryEffects::Other: + OS << "Other: "; + break; + } + OS << ME.getModRef(Loc) << ", "; + } + return OS; +} + +//===----------------------------------------------------------------------===// +// Helper method implementation +//===----------------------------------------------------------------------===// + +ModRefInfo AAResults::getModRefInfo(const LoadInst *L, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + // Be conservative in the face of atomic. + if (isStrongerThan(L->getOrdering(), AtomicOrdering::Unordered)) + return ModRefInfo::ModRef; + + // If the load address doesn't alias the given address, it doesn't read + // or write the specified memory. + if (Loc.Ptr) { + AliasResult AR = alias(MemoryLocation::get(L), Loc, AAQI, L); + if (AR == AliasResult::NoAlias) + return ModRefInfo::NoModRef; + } + // Otherwise, a load just reads. + return ModRefInfo::Ref; +} + +ModRefInfo AAResults::getModRefInfo(const StoreInst *S, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + // Be conservative in the face of atomic. + if (isStrongerThan(S->getOrdering(), AtomicOrdering::Unordered)) + return ModRefInfo::ModRef; + + if (Loc.Ptr) { + AliasResult AR = alias(MemoryLocation::get(S), Loc, AAQI, S); + // If the store address cannot alias the pointer in question, then the + // specified memory cannot be modified by the store. + if (AR == AliasResult::NoAlias) + return ModRefInfo::NoModRef; + + // Examine the ModRef mask. If Mod isn't present, then return NoModRef. + // This ensures that if Loc is a constant memory location, we take into + // account the fact that the store definitely could not modify the memory + // location. + if (!isModSet(getModRefInfoMask(Loc))) + return ModRefInfo::NoModRef; + } + + // Otherwise, a store just writes. + return ModRefInfo::Mod; +} + +ModRefInfo AAResults::getModRefInfo(const FenceInst *S, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + // All we know about a fence instruction is what we get from the ModRef + // mask: if Loc is a constant memory location, the fence definitely could + // not modify it. + if (Loc.Ptr) + return getModRefInfoMask(Loc); + return ModRefInfo::ModRef; +} + +ModRefInfo AAResults::getModRefInfo(const VAArgInst *V, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + if (Loc.Ptr) { + AliasResult AR = alias(MemoryLocation::get(V), Loc, AAQI, V); + // If the va_arg address cannot alias the pointer in question, then the + // specified memory cannot be accessed by the va_arg. + if (AR == AliasResult::NoAlias) + return ModRefInfo::NoModRef; + + // If the pointer is a pointer to invariant memory, then it could not have + // been modified by this va_arg. + return getModRefInfoMask(Loc, AAQI); + } + + // Otherwise, a va_arg reads and writes. + return ModRefInfo::ModRef; +} + +ModRefInfo AAResults::getModRefInfo(const CatchPadInst *CatchPad, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + if (Loc.Ptr) { + // If the pointer is a pointer to invariant memory, + // then it could not have been modified by this catchpad. + return getModRefInfoMask(Loc, AAQI); + } + + // Otherwise, a catchpad reads and writes. + return ModRefInfo::ModRef; +} + +ModRefInfo AAResults::getModRefInfo(const CatchReturnInst *CatchRet, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + if (Loc.Ptr) { + // If the pointer is a pointer to invariant memory, + // then it could not have been modified by this catchpad. + return getModRefInfoMask(Loc, AAQI); + } + + // Otherwise, a catchret reads and writes. + return ModRefInfo::ModRef; +} + +ModRefInfo AAResults::getModRefInfo(const AtomicCmpXchgInst *CX, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + // Acquire/Release cmpxchg has properties that matter for arbitrary addresses. + if (isStrongerThanMonotonic(CX->getSuccessOrdering())) + return ModRefInfo::ModRef; + + if (Loc.Ptr) { + AliasResult AR = alias(MemoryLocation::get(CX), Loc, AAQI, CX); + // If the cmpxchg address does not alias the location, it does not access + // it. + if (AR == AliasResult::NoAlias) + return ModRefInfo::NoModRef; + } + + return ModRefInfo::ModRef; +} + +ModRefInfo AAResults::getModRefInfo(const AtomicRMWInst *RMW, + const MemoryLocation &Loc, + AAQueryInfo &AAQI) { + // Acquire/Release atomicrmw has properties that matter for arbitrary addresses. + if (isStrongerThanMonotonic(RMW->getOrdering())) + return ModRefInfo::ModRef; + + if (Loc.Ptr) { + AliasResult AR = alias(MemoryLocation::get(RMW), Loc, AAQI, RMW); + // If the atomicrmw address does not alias the location, it does not access + // it. + if (AR == AliasResult::NoAlias) + return ModRefInfo::NoModRef; + } + + return ModRefInfo::ModRef; +} + +ModRefInfo AAResults::getModRefInfo(const Instruction *I, + const std::optional<MemoryLocation> &OptLoc, + AAQueryInfo &AAQIP) { + if (OptLoc == std::nullopt) { + if (const auto *Call = dyn_cast<CallBase>(I)) + return getMemoryEffects(Call, AAQIP).getModRef(); + } + + const MemoryLocation &Loc = OptLoc.value_or(MemoryLocation()); + + switch (I->getOpcode()) { + case Instruction::VAArg: + return getModRefInfo((const VAArgInst *)I, Loc, AAQIP); + case Instruction::Load: + return getModRefInfo((const LoadInst *)I, Loc, AAQIP); + case Instruction::Store: + return getModRefInfo((const StoreInst *)I, Loc, AAQIP); + case Instruction::Fence: + return getModRefInfo((const FenceInst *)I, Loc, AAQIP); + case Instruction::AtomicCmpXchg: + return getModRefInfo((const AtomicCmpXchgInst *)I, Loc, AAQIP); + case Instruction::AtomicRMW: + return getModRefInfo((const AtomicRMWInst *)I, Loc, AAQIP); + case Instruction::Call: + case Instruction::CallBr: + case Instruction::Invoke: + return getModRefInfo((const CallBase *)I, Loc, AAQIP); + case Instruction::CatchPad: + return getModRefInfo((const CatchPadInst *)I, Loc, AAQIP); + case Instruction::CatchRet: + return getModRefInfo((const CatchReturnInst *)I, Loc, AAQIP); + default: + assert(!I->mayReadOrWriteMemory() && + "Unhandled memory access instruction!"); + return ModRefInfo::NoModRef; + } +} + +/// Return information about whether a particular call site modifies +/// or reads the specified memory location \p MemLoc before instruction \p I +/// in a BasicBlock. +/// 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 AAResults::callCapturesBefore(const Instruction *I, + const MemoryLocation &MemLoc, + DominatorTree *DT, + AAQueryInfo &AAQI) { + if (!DT) + return ModRefInfo::ModRef; + + const Value *Object = getUnderlyingObject(MemLoc.Ptr); + if (!isIdentifiedFunctionLocal(Object)) + return ModRefInfo::ModRef; + + const auto *Call = dyn_cast<CallBase>(I); + if (!Call || Call == Object) + return ModRefInfo::ModRef; + + if (PointerMayBeCapturedBefore(Object, /* ReturnCaptures */ true, + /* StoreCaptures */ true, I, DT, + /* include Object */ true)) + return ModRefInfo::ModRef; + + unsigned ArgNo = 0; + ModRefInfo R = ModRefInfo::NoModRef; + // Set flag only if no May found and all operands processed. + for (auto CI = Call->data_operands_begin(), CE = Call->data_operands_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() || + (!Call->doesNotCapture(ArgNo) && ArgNo < Call->arg_size() && + !Call->isByValArgument(ArgNo))) + continue; + + AliasResult AR = + alias(MemoryLocation::getBeforeOrAfter(*CI), + MemoryLocation::getBeforeOrAfter(Object), AAQI, Call); + // 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 (AR == AliasResult::NoAlias) + continue; + if (Call->doesNotAccessMemory(ArgNo)) + continue; + if (Call->onlyReadsMemory(ArgNo)) { + R = ModRefInfo::Ref; + continue; + } + return ModRefInfo::ModRef; + } + return R; +} + +/// canBasicBlockModify - Return true if it is possible for execution of the +/// specified basic block to modify the location Loc. +/// +bool AAResults::canBasicBlockModify(const BasicBlock &BB, + const MemoryLocation &Loc) { + return canInstructionRangeModRef(BB.front(), BB.back(), Loc, ModRefInfo::Mod); +} + +/// 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 AAResults::canInstructionRangeModRef(const Instruction &I1, + const Instruction &I2, + const MemoryLocation &Loc, + const ModRefInfo Mode) { + assert(I1.getParent() == I2.getParent() && + "Instructions not in same basic block!"); + BasicBlock::const_iterator I = I1.getIterator(); + BasicBlock::const_iterator E = I2.getIterator(); + ++E; // Convert from inclusive to exclusive range. + + for (; I != E; ++I) // Check every instruction in range + if (isModOrRefSet(getModRefInfo(&*I, Loc) & Mode)) + return true; + return false; +} + +// Provide a definition for the root virtual destructor. +AAResults::Concept::~Concept() = default; + +// Provide a definition for the static object used to identify passes. +AnalysisKey AAManager::Key; + +ExternalAAWrapperPass::ExternalAAWrapperPass() : ImmutablePass(ID) { + initializeExternalAAWrapperPassPass(*PassRegistry::getPassRegistry()); +} + +ExternalAAWrapperPass::ExternalAAWrapperPass(CallbackT CB) + : ImmutablePass(ID), CB(std::move(CB)) { + initializeExternalAAWrapperPassPass(*PassRegistry::getPassRegistry()); +} + +char ExternalAAWrapperPass::ID = 0; + +INITIALIZE_PASS(ExternalAAWrapperPass, "external-aa", "External Alias Analysis", + false, true) + +ImmutablePass * +llvm::createExternalAAWrapperPass(ExternalAAWrapperPass::CallbackT Callback) { + return new ExternalAAWrapperPass(std::move(Callback)); +} + +AAResultsWrapperPass::AAResultsWrapperPass() : FunctionPass(ID) { + initializeAAResultsWrapperPassPass(*PassRegistry::getPassRegistry()); +} + +char AAResultsWrapperPass::ID = 0; + +INITIALIZE_PASS_BEGIN(AAResultsWrapperPass, "aa", + "Function Alias Analysis Results", false, true) +INITIALIZE_PASS_DEPENDENCY(BasicAAWrapperPass) +INITIALIZE_PASS_DEPENDENCY(ExternalAAWrapperPass) +INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass) +INITIALIZE_PASS_DEPENDENCY(SCEVAAWrapperPass) +INITIALIZE_PASS_DEPENDENCY(ScopedNoAliasAAWrapperPass) +INITIALIZE_PASS_DEPENDENCY(TypeBasedAAWrapperPass) +INITIALIZE_PASS_END(AAResultsWrapperPass, "aa", + "Function Alias Analysis Results", false, true) + +FunctionPass *llvm::createAAResultsWrapperPass() { + return new AAResultsWrapperPass(); +} + +/// Run the wrapper pass to rebuild an aggregation over known AA passes. +/// +/// This is the legacy pass manager's interface to the new-style AA results +/// aggregation object. Because this is somewhat shoe-horned into the legacy +/// pass manager, we hard code all the specific alias analyses available into +/// it. While the particular set enabled is configured via commandline flags, +/// adding a new alias analysis to LLVM will require adding support for it to +/// this list. +bool AAResultsWrapperPass::runOnFunction(Function &F) { + // NB! This *must* be reset before adding new AA results to the new + // AAResults object because in the legacy pass manager, each instance + // of these will refer to the *same* immutable analyses, registering and + // unregistering themselves with them. We need to carefully tear down the + // previous object first, in this case replacing it with an empty one, before + // registering new results. + AAR.reset( + new AAResults(getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F))); + + // BasicAA is always available for function analyses. Also, we add it first + // so that it can trump TBAA results when it proves MustAlias. + // FIXME: TBAA should have an explicit mode to support this and then we + // should reconsider the ordering here. + if (!DisableBasicAA) + AAR->addAAResult(getAnalysis<BasicAAWrapperPass>().getResult()); + + // Populate the results with the currently available AAs. + if (auto *WrapperPass = getAnalysisIfAvailable<ScopedNoAliasAAWrapperPass>()) + AAR->addAAResult(WrapperPass->getResult()); + if (auto *WrapperPass = getAnalysisIfAvailable<TypeBasedAAWrapperPass>()) + AAR->addAAResult(WrapperPass->getResult()); + if (auto *WrapperPass = getAnalysisIfAvailable<GlobalsAAWrapperPass>()) + AAR->addAAResult(WrapperPass->getResult()); + if (auto *WrapperPass = getAnalysisIfAvailable<SCEVAAWrapperPass>()) + AAR->addAAResult(WrapperPass->getResult()); + + // If available, run an external AA providing callback over the results as + // well. + if (auto *WrapperPass = getAnalysisIfAvailable<ExternalAAWrapperPass>()) + if (WrapperPass->CB) + WrapperPass->CB(*this, F, *AAR); + + // Analyses don't mutate the IR, so return false. + return false; +} + +void AAResultsWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesAll(); + AU.addRequiredTransitive<BasicAAWrapperPass>(); + AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>(); + + // We also need to mark all the alias analysis passes we will potentially + // probe in runOnFunction as used here to ensure the legacy pass manager + // preserves them. This hard coding of lists of alias analyses is specific to + // the legacy pass manager. + AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>(); + AU.addUsedIfAvailable<TypeBasedAAWrapperPass>(); + AU.addUsedIfAvailable<GlobalsAAWrapperPass>(); + AU.addUsedIfAvailable<SCEVAAWrapperPass>(); + AU.addUsedIfAvailable<ExternalAAWrapperPass>(); +} + +AAManager::Result AAManager::run(Function &F, FunctionAnalysisManager &AM) { + Result R(AM.getResult<TargetLibraryAnalysis>(F)); + for (auto &Getter : ResultGetters) + (*Getter)(F, AM, R); + return R; +} + +AAResults llvm::createLegacyPMAAResults(Pass &P, Function &F, + BasicAAResult &BAR) { + AAResults AAR(P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F)); + + // Add in our explicitly constructed BasicAA results. + if (!DisableBasicAA) + AAR.addAAResult(BAR); + + // Populate the results with the other currently available AAs. + if (auto *WrapperPass = + P.getAnalysisIfAvailable<ScopedNoAliasAAWrapperPass>()) + AAR.addAAResult(WrapperPass->getResult()); + if (auto *WrapperPass = P.getAnalysisIfAvailable<TypeBasedAAWrapperPass>()) + AAR.addAAResult(WrapperPass->getResult()); + if (auto *WrapperPass = P.getAnalysisIfAvailable<GlobalsAAWrapperPass>()) + AAR.addAAResult(WrapperPass->getResult()); + if (auto *WrapperPass = P.getAnalysisIfAvailable<ExternalAAWrapperPass>()) + if (WrapperPass->CB) + WrapperPass->CB(P, F, AAR); + + return AAR; +} + +bool llvm::isNoAliasCall(const Value *V) { + if (const auto *Call = dyn_cast<CallBase>(V)) + return Call->hasRetAttr(Attribute::NoAlias); + return false; +} + +static bool isNoAliasOrByValArgument(const Value *V) { + if (const Argument *A = dyn_cast<Argument>(V)) + return A->hasNoAliasAttr() || A->hasByValAttr(); + return false; +} + +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 (isNoAliasOrByValArgument(V)) + return true; + return false; +} + +bool llvm::isIdentifiedFunctionLocal(const Value *V) { + return isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasOrByValArgument(V); +} + +bool llvm::isEscapeSource(const Value *V) { + if (auto *CB = dyn_cast<CallBase>(V)) + return !isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(CB, + true); + + // The load case works because isNonEscapingLocalObject considers all + // stores to be escapes (it passes true for the StoreCaptures argument + // to PointerMayBeCaptured). + if (isa<LoadInst>(V)) + return true; + + // The inttoptr case works because isNonEscapingLocalObject considers all + // means of converting or equating a pointer to an int (ptrtoint, ptr store + // which could be followed by an integer load, ptr<->int compare) as + // escaping, and objects located at well-known addresses via platform-specific + // means cannot be considered non-escaping local objects. + if (isa<IntToPtrInst>(V)) + return true; + + return false; +} + +bool llvm::isNotVisibleOnUnwind(const Value *Object, + bool &RequiresNoCaptureBeforeUnwind) { + RequiresNoCaptureBeforeUnwind = false; + + // Alloca goes out of scope on unwind. + if (isa<AllocaInst>(Object)) + return true; + + // Byval goes out of scope on unwind. + if (auto *A = dyn_cast<Argument>(Object)) + return A->hasByValAttr(); + + // A noalias return is not accessible from any other code. If the pointer + // does not escape prior to the unwind, then the caller cannot access the + // memory either. + if (isNoAliasCall(Object)) { + RequiresNoCaptureBeforeUnwind = true; + return true; + } + + return false; +} + +void llvm::getAAResultsAnalysisUsage(AnalysisUsage &AU) { + // This function needs to be in sync with llvm::createLegacyPMAAResults -- if + // more alias analyses are added to llvm::createLegacyPMAAResults, they need + // to be added here also. + AU.addRequired<TargetLibraryInfoWrapperPass>(); + AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>(); + AU.addUsedIfAvailable<TypeBasedAAWrapperPass>(); + AU.addUsedIfAvailable<GlobalsAAWrapperPass>(); + AU.addUsedIfAvailable<ExternalAAWrapperPass>(); +} |