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llvm-mirror/lib/Analysis/AliasAnalysis.cpp
Nikita Popov a09a84aaf6 [AA] Support callCapturesBefore() on BatchAA (NFCI) 
This is not expected to have any practical compile-time effect,
as the alias() calls inside callCapturesBefore() are rare. This
should still be supported for API completeness, and might be
useful for reachability caching.
2021-05-14 21:48:08 +02:00

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//==- 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/CFLAndersAliasAnalysis.h"
#include "llvm/Analysis/CFLSteensAliasAnalysis.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/Module.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)) {
for (auto &AA : AAs)
AA->setAAResults(this);
}
AAResults::~AAResults() {
// FIXME; It would be nice to at least clear out the pointers back to this
// aggregation here, but we end up with non-nesting lifetimes in the legacy
// pass manager that prevent this from working. In the legacy pass manager
// we'll end up with dangling references here in some cases.
#if 0
for (auto &AA : AAs)
AA->setAAResults(nullptr);
#endif
}
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) {
AAQueryInfo AAQIP;
return alias(LocA, LocB, AAQIP);
}
AliasResult AAResults::alias(const MemoryLocation &LocA,
const MemoryLocation &LocB, AAQueryInfo &AAQI) {
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);
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;
}
bool AAResults::pointsToConstantMemory(const MemoryLocation &Loc,
bool OrLocal) {
AAQueryInfo AAQIP;
return pointsToConstantMemory(Loc, AAQIP, OrLocal);
}
bool AAResults::pointsToConstantMemory(const MemoryLocation &Loc,
AAQueryInfo &AAQI, bool OrLocal) {
for (const auto &AA : AAs)
if (AA->pointsToConstantMemory(Loc, AAQI, OrLocal))
return true;
return false;
}
ModRefInfo AAResults::getArgModRefInfo(const CallBase *Call, unsigned ArgIdx) {
ModRefInfo Result = ModRefInfo::ModRef;
for (const auto &AA : AAs) {
Result = intersectModRef(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(Instruction *I, const CallBase *Call2) {
AAQueryInfo AAQIP;
return getModRefInfo(I, Call2, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(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);
} else if (I->isFenceLike()) {
// If this is a fence, just return ModRef.
return ModRefInfo::ModRef;
} 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);
ModRefInfo MR = getModRefInfo(Call2, DefLoc, AAQI);
if (isModOrRefSet(MR))
return setModAndRef(MR);
}
return ModRefInfo::NoModRef;
}
ModRefInfo AAResults::getModRefInfo(const CallBase *Call,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(Call, Loc, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(const CallBase *Call,
const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
ModRefInfo Result = ModRefInfo::ModRef;
for (const auto &AA : AAs) {
Result = intersectModRef(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.
auto MRB = getModRefBehavior(Call);
if (onlyAccessesInaccessibleMem(MRB))
return ModRefInfo::NoModRef;
if (onlyReadsMemory(MRB))
Result = clearMod(Result);
else if (doesNotReadMemory(MRB))
Result = clearRef(Result);
if (onlyAccessesArgPointees(MRB) || onlyAccessesInaccessibleOrArgMem(MRB)) {
bool IsMustAlias = true;
ModRefInfo AllArgsMask = ModRefInfo::NoModRef;
if (doesAccessArgPointees(MRB)) {
for (auto AI = Call->arg_begin(), AE = Call->arg_end(); AI != AE; ++AI) {
const Value *Arg = *AI;
if (!Arg->getType()->isPointerTy())
continue;
unsigned ArgIdx = std::distance(Call->arg_begin(), AI);
MemoryLocation ArgLoc =
MemoryLocation::getForArgument(Call, ArgIdx, TLI);
AliasResult ArgAlias = alias(ArgLoc, Loc, AAQI);
if (ArgAlias != AliasResult::NoAlias) {
ModRefInfo ArgMask = getArgModRefInfo(Call, ArgIdx);
AllArgsMask = unionModRef(AllArgsMask, ArgMask);
}
// Conservatively clear IsMustAlias unless only MustAlias is found.
IsMustAlias &= (ArgAlias == AliasResult::MustAlias);
}
}
// Return NoModRef if no alias found with any argument.
if (isNoModRef(AllArgsMask))
return ModRefInfo::NoModRef;
// Logical & between other AA analyses and argument analysis.
Result = intersectModRef(Result, AllArgsMask);
// If only MustAlias found above, set Must bit.
Result = IsMustAlias ? setMust(Result) : clearMust(Result);
}
// If Loc is a constant memory location, the call definitely could not
// modify the memory location.
if (isModSet(Result) && pointsToConstantMemory(Loc, AAQI, /*OrLocal*/ false))
Result = clearMod(Result);
return Result;
}
ModRefInfo AAResults::getModRefInfo(const CallBase *Call1,
const CallBase *Call2) {
AAQueryInfo AAQIP;
return getModRefInfo(Call1, Call2, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(const CallBase *Call1,
const CallBase *Call2, AAQueryInfo &AAQI) {
ModRefInfo Result = ModRefInfo::ModRef;
for (const auto &AA : AAs) {
Result = intersectModRef(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 = getModRefBehavior(Call1);
if (Call1B == FMRB_DoesNotAccessMemory)
return ModRefInfo::NoModRef;
auto Call2B = getModRefBehavior(Call2);
if (Call2B == FMRB_DoesNotAccessMemory)
return ModRefInfo::NoModRef;
// If they both only read from memory, there is no dependence.
if (onlyReadsMemory(Call1B) && onlyReadsMemory(Call2B))
return ModRefInfo::NoModRef;
// If Call1 only reads memory, the only dependence on Call2 can be
// from Call1 reading memory written by Call2.
if (onlyReadsMemory(Call1B))
Result = clearMod(Result);
else if (doesNotReadMemory(Call1B))
Result = clearRef(Result);
// 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 (onlyAccessesArgPointees(Call2B)) {
if (!doesAccessArgPointees(Call2B))
return ModRefInfo::NoModRef;
ModRefInfo R = ModRefInfo::NoModRef;
bool IsMustAlias = true;
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.
ModRefInfo ModRefC1 = getModRefInfo(Call1, Call2ArgLoc, AAQI);
ArgMask = intersectModRef(ArgMask, ModRefC1);
// Conservatively clear IsMustAlias unless only MustAlias is found.
IsMustAlias &= isMustSet(ModRefC1);
R = intersectModRef(unionModRef(R, ArgMask), Result);
if (R == Result) {
// On early exit, not all args were checked, cannot set Must.
if (I + 1 != E)
IsMustAlias = false;
break;
}
}
if (isNoModRef(R))
return ModRefInfo::NoModRef;
// If MustAlias found above, set Must bit.
return IsMustAlias ? setMust(R) : clearMust(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 (onlyAccessesArgPointees(Call1B)) {
if (!doesAccessArgPointees(Call1B))
return ModRefInfo::NoModRef;
ModRefInfo R = ModRefInfo::NoModRef;
bool IsMustAlias = true;
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 = intersectModRef(unionModRef(R, ArgModRefC1), Result);
// Conservatively clear IsMustAlias unless only MustAlias is found.
IsMustAlias &= isMustSet(ModRefC2);
if (R == Result) {
// On early exit, not all args were checked, cannot set Must.
if (I + 1 != E)
IsMustAlias = false;
break;
}
}
if (isNoModRef(R))
return ModRefInfo::NoModRef;
// If MustAlias found above, set Must bit.
return IsMustAlias ? setMust(R) : clearMust(R);
}
return Result;
}
FunctionModRefBehavior AAResults::getModRefBehavior(const CallBase *Call) {
FunctionModRefBehavior Result = FMRB_UnknownModRefBehavior;
for (const auto &AA : AAs) {
Result = FunctionModRefBehavior(Result & AA->getModRefBehavior(Call));
// Early-exit the moment we reach the bottom of the lattice.
if (Result == FMRB_DoesNotAccessMemory)
return Result;
}
return Result;
}
FunctionModRefBehavior AAResults::getModRefBehavior(const Function *F) {
FunctionModRefBehavior Result = FMRB_UnknownModRefBehavior;
for (const auto &AA : AAs) {
Result = FunctionModRefBehavior(Result & AA->getModRefBehavior(F));
// Early-exit the moment we reach the bottom of the lattice.
if (Result == FMRB_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;
}
//===----------------------------------------------------------------------===//
// Helper method implementation
//===----------------------------------------------------------------------===//
ModRefInfo AAResults::getModRefInfo(const LoadInst *L,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(L, Loc, AAQIP);
}
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);
if (AR == AliasResult::NoAlias)
return ModRefInfo::NoModRef;
if (AR == AliasResult::MustAlias)
return ModRefInfo::MustRef;
}
// Otherwise, a load just reads.
return ModRefInfo::Ref;
}
ModRefInfo AAResults::getModRefInfo(const StoreInst *S,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(S, Loc, AAQIP);
}
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);
// 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;
// If the pointer is a pointer to constant memory, then it could not have
// been modified by this store.
if (pointsToConstantMemory(Loc, AAQI))
return ModRefInfo::NoModRef;
// If the store address aliases the pointer as must alias, set Must.
if (AR == AliasResult::MustAlias)
return ModRefInfo::MustMod;
}
// Otherwise, a store just writes.
return ModRefInfo::Mod;
}
ModRefInfo AAResults::getModRefInfo(const FenceInst *S, const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(S, Loc, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(const FenceInst *S,
const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
// If we know that the location is a constant memory location, the fence
// cannot modify this location.
if (Loc.Ptr && pointsToConstantMemory(Loc, AAQI))
return ModRefInfo::Ref;
return ModRefInfo::ModRef;
}
ModRefInfo AAResults::getModRefInfo(const VAArgInst *V,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(V, Loc, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(const VAArgInst *V,
const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
if (Loc.Ptr) {
AliasResult AR = alias(MemoryLocation::get(V), Loc, AAQI);
// 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 constant memory, then it could not have
// been modified by this va_arg.
if (pointsToConstantMemory(Loc, AAQI))
return ModRefInfo::NoModRef;
// If the va_arg aliases the pointer as must alias, set Must.
if (AR == AliasResult::MustAlias)
return ModRefInfo::MustModRef;
}
// Otherwise, a va_arg reads and writes.
return ModRefInfo::ModRef;
}
ModRefInfo AAResults::getModRefInfo(const CatchPadInst *CatchPad,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(CatchPad, Loc, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(const CatchPadInst *CatchPad,
const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
if (Loc.Ptr) {
// If the pointer is a pointer to constant memory,
// then it could not have been modified by this catchpad.
if (pointsToConstantMemory(Loc, AAQI))
return ModRefInfo::NoModRef;
}
// Otherwise, a catchpad reads and writes.
return ModRefInfo::ModRef;
}
ModRefInfo AAResults::getModRefInfo(const CatchReturnInst *CatchRet,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(CatchRet, Loc, AAQIP);
}
ModRefInfo AAResults::getModRefInfo(const CatchReturnInst *CatchRet,
const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
if (Loc.Ptr) {
// If the pointer is a pointer to constant memory,
// then it could not have been modified by this catchpad.
if (pointsToConstantMemory(Loc, AAQI))
return ModRefInfo::NoModRef;
}
// Otherwise, a catchret reads and writes.
return ModRefInfo::ModRef;
}
ModRefInfo AAResults::getModRefInfo(const AtomicCmpXchgInst *CX,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(CX, Loc, AAQIP);
}
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);
// If the cmpxchg address does not alias the location, it does not access
// it.
if (AR == AliasResult::NoAlias)
return ModRefInfo::NoModRef;
// If the cmpxchg address aliases the pointer as must alias, set Must.
if (AR == AliasResult::MustAlias)
return ModRefInfo::MustModRef;
}
return ModRefInfo::ModRef;
}
ModRefInfo AAResults::getModRefInfo(const AtomicRMWInst *RMW,
const MemoryLocation &Loc) {
AAQueryInfo AAQIP;
return getModRefInfo(RMW, Loc, AAQIP);
}
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);
// If the atomicrmw address does not alias the location, it does not access
// it.
if (AR == AliasResult::NoAlias)
return ModRefInfo::NoModRef;
// If the atomicrmw address aliases the pointer as must alias, set Must.
if (AR == AliasResult::MustAlias)
return ModRefInfo::MustModRef;
}
return ModRefInfo::ModRef;
}
ModRefInfo AAResults::getModRefInfo(const Instruction *I,
const Optional<MemoryLocation> &OptLoc,
AAQueryInfo &AAQIP) {
if (OptLoc == None) {
if (const auto *Call = dyn_cast<CallBase>(I)) {
return createModRefInfo(getModRefBehavior(Call));
}
}
const MemoryLocation &Loc = OptLoc.getValueOr(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:
return getModRefInfo((const CallInst *)I, Loc, AAQIP);
case Instruction::Invoke:
return getModRefInfo((const InvokeInst *)I, Loc, AAQIP);
case Instruction::CatchPad:
return getModRefInfo((const CatchPadInst *)I, Loc, AAQIP);
case Instruction::CatchRet:
return getModRefInfo((const CatchReturnInst *)I, Loc, AAQIP);
default:
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;
bool IsMustAlias = true;
// 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->getNumArgOperands() &&
!Call->isByValArgument(ArgNo)))
continue;
AliasResult AR = alias(
MemoryLocation::getBeforeOrAfter(*CI),
MemoryLocation::getBeforeOrAfter(Object), AAQI);
// 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::MustAlias)
IsMustAlias = false;
if (AR == AliasResult::NoAlias)
continue;
if (Call->doesNotAccessMemory(ArgNo))
continue;
if (Call->onlyReadsMemory(ArgNo)) {
R = ModRefInfo::Ref;
continue;
}
// Not returning MustModRef since we have not seen all the arguments.
return ModRefInfo::ModRef;
}
return IsMustAlias ? setMust(R) : clearMust(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(intersectModRef(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;
namespace {
} // end anonymous namespace
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(CFLAndersAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(CFLSteensAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ExternalAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ObjCARCAAWrapperPass)
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<objcarc::ObjCARCAAWrapperPass>())
AAR->addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = getAnalysisIfAvailable<GlobalsAAWrapperPass>())
AAR->addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = getAnalysisIfAvailable<SCEVAAWrapperPass>())
AAR->addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = getAnalysisIfAvailable<CFLAndersAAWrapperPass>())
AAR->addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = getAnalysisIfAvailable<CFLSteensAAWrapperPass>())
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<objcarc::ObjCARCAAWrapperPass>();
AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
AU.addUsedIfAvailable<SCEVAAWrapperPass>();
AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
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<objcarc::ObjCARCAAWrapperPass>())
AAR.addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = P.getAnalysisIfAvailable<GlobalsAAWrapperPass>())
AAR.addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLAndersAAWrapperPass>())
AAR.addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLSteensAAWrapperPass>())
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);
}
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<objcarc::ObjCARCAAWrapperPass>();
AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
AU.addUsedIfAvailable<ExternalAAWrapperPass>();
}
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