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llvm-mirror/lib/Analysis/AliasAnalysis.cpp
Nikita Popov 4cddc2f391 [AA] byval argument is identified function local 
byval arguments should mostly get the same treatment as noalias
arguments in alias analysis. This was not the case for the
isIdentifiedFunctionLocal() function.

Marking byval arguments as identified function local means that
they cannot alias with other arguments, which I believe is correct.

Differential Revision: https://reviews.llvm.org/D93602
2020-12-21 20:18:23 +01:00

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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");
/// 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));
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 = MayAlias;
Depth++;
for (const auto &AA : AAs) {
Result = AA->alias(LocA, LocB, AAQI);
if (Result != MayAlias)
break;
}
Depth--;
if (Depth == 0) {
if (Result == NoAlias)
++NumNoAlias;
else if (Result == 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 != NoAlias) {
ModRefInfo ArgMask = getArgModRefInfo(Call, ArgIdx);
AllArgsMask = unionModRef(AllArgsMask, ArgMask);
}
// Conservatively clear IsMustAlias unless only MustAlias is found.
IsMustAlias &= (ArgAlias == 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 NoAlias:
OS << "NoAlias";
break;
case MustAlias:
OS << "MustAlias";
break;
case MayAlias:
OS << "MayAlias";
break;
case PartialAlias:
OS << "PartialAlias";
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 == NoAlias)
return ModRefInfo::NoModRef;
if (AR == 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 == 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 == 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 == 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 == 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 == NoAlias)
return ModRefInfo::NoModRef;
// If the cmpxchg address aliases the pointer as must alias, set Must.
if (AR == 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 == NoAlias)
return ModRefInfo::NoModRef;
// If the atomicrmw address aliases the pointer as must alias, set Must.
if (AR == 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) {
if (!DT)
return ModRefInfo::ModRef;
const Value *Object = getUnderlyingObject(MemLoc.Ptr);
if (!isIdentifiedObject(Object) || isa<GlobalValue>(Object) ||
isa<Constant>(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(*CI, Object);
// 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 != MustAlias)
IsMustAlias = false;
if (AR == 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.addRequired<BasicAAWrapperPass>();
AU.addRequired<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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