AAResults llvm::createLegacyPMAAResults(Pass &P, Function &F,
BasicAAResult &BAR) {
AAResults AAR;
// 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<SCEVAAWrapperPass>())
AAR.addAAResult(WrapperPass->getResult());
if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLAAWrapperPass>())
AAR.addAAResult(WrapperPass->getResult());
return AAR;
}
/// Returns the memory access attribute for function F using AAR for AA results,
/// where SCCNodes is the current SCC.
///
/// If ThisBody is true, this function may examine the function body and will
/// return a result pertaining to this copy of the function. If it is false, the
/// result will be based only on AA results for the function declaration; it
/// will be assumed that some other (perhaps less optimized) version of the
/// function may be selected at link time.
static MemoryAccessKind checkFunctionMemoryAccess(Function &F, bool ThisBody,
AAResults &AAR,
const SCCNodeSet &SCCNodes) {
FunctionModRefBehavior MRB = AAR.getModRefBehavior(&F);
if (MRB == FMRB_DoesNotAccessMemory)
// Already perfect!
return MAK_ReadNone;
if (!ThisBody) {
if (AliasAnalysis::onlyReadsMemory(MRB))
return MAK_ReadOnly;
// Conservatively assume it writes to memory.
return MAK_MayWrite;
}
// Scan the function body for instructions that may read or write memory.
bool ReadsMemory = false;
for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
Instruction *I = &*II;
// Some instructions can be ignored even if they read or write memory.
// Detect these now, skipping to the next instruction if one is found.
CallSite CS(cast<Value>(I));
if (CS) {
// Ignore calls to functions in the same SCC, as long as the call sites
// don't have operand bundles. Calls with operand bundles are allowed to
// have memory effects not described by the memory effects of the call
// target.
if (!CS.hasOperandBundles() && CS.getCalledFunction() &&
SCCNodes.count(CS.getCalledFunction()))
continue;
FunctionModRefBehavior MRB = AAR.getModRefBehavior(CS);
// If the call doesn't access memory, we're done.
if (!(MRB & MRI_ModRef))
continue;
if (!AliasAnalysis::onlyAccessesArgPointees(MRB)) {
// The call could access any memory. If that includes writes, give up.
if (MRB & MRI_Mod)
return MAK_MayWrite;
// If it reads, note it.
if (MRB & MRI_Ref)
ReadsMemory = true;
continue;
}
// Check whether all pointer arguments point to local memory, and
// ignore calls that only access local memory.
for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
CI != CE; ++CI) {
Value *Arg = *CI;
if (!Arg->getType()->isPtrOrPtrVectorTy())
continue;
AAMDNodes AAInfo;
I->getAAMetadata(AAInfo);
MemoryLocation Loc(Arg, MemoryLocation::UnknownSize, AAInfo);
// Skip accesses to local or constant memory as they don't impact the
// externally visible mod/ref behavior.
if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
continue;
if (MRB & MRI_Mod)
// Writes non-local memory. Give up.
return MAK_MayWrite;
if (MRB & MRI_Ref)
// Ok, it reads non-local memory.
ReadsMemory = true;
}
continue;
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
// Ignore non-volatile loads from local memory. (Atomic is okay here.)
if (!LI->isVolatile()) {
MemoryLocation Loc = MemoryLocation::get(LI);
if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
continue;
}
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
// Ignore non-volatile stores to local memory. (Atomic is okay here.)
if (!SI->isVolatile()) {
MemoryLocation Loc = MemoryLocation::get(SI);
if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
continue;
}
} else if (VAArgInst *VI = dyn_cast<VAArgInst>(I)) {
// Ignore vaargs on local memory.
MemoryLocation Loc = MemoryLocation::get(VI);
if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
continue;
}
// Any remaining instructions need to be taken seriously! Check if they
// read or write memory.
if (I->mayWriteToMemory())
// Writes memory. Just give up.
return MAK_MayWrite;
// If this instruction may read memory, remember that.
ReadsMemory |= I->mayReadFromMemory();
}
return ReadsMemory ? MAK_ReadOnly : MAK_ReadNone;
}
// See if any operand of the call instruction references the coroutine frame.
static bool operandReferences(CallInst *CI, AllocaInst *Frame, AAResults &AA) {
for (Value *Op : CI->operand_values())
if (AA.alias(Op, Frame) != NoAlias)
return true;
return false;
}
/// isSafeToPromoteArgument - As you might guess from the name of this method,
/// it checks to see if it is both safe and useful to promote the argument.
/// This method limits promotion of aggregates to only promote up to three
/// elements of the aggregate in order to avoid exploding the number of
/// arguments passed in.
bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg,
bool isByValOrInAlloca,
AAResults &AAR) const {
typedef std::set<IndicesVector> GEPIndicesSet;
// Quick exit for unused arguments
if (Arg->use_empty())
return true;
// We can only promote this argument if all of the uses are loads, or are GEP
// instructions (with constant indices) that are subsequently loaded.
//
// Promoting the argument causes it to be loaded in the caller
// unconditionally. This is only safe if we can prove that either the load
// would have happened in the callee anyway (ie, there is a load in the entry
// block) or the pointer passed in at every call site is guaranteed to be
// valid.
// In the former case, invalid loads can happen, but would have happened
// anyway, in the latter case, invalid loads won't happen. This prevents us
// from introducing an invalid load that wouldn't have happened in the
// original code.
//
// This set will contain all sets of indices that are loaded in the entry
// block, and thus are safe to unconditionally load in the caller.
//
// This optimization is also safe for InAlloca parameters, because it verifies
// that the address isn't captured.
GEPIndicesSet SafeToUnconditionallyLoad;
// This set contains all the sets of indices that we are planning to promote.
// This makes it possible to limit the number of arguments added.
GEPIndicesSet ToPromote;
// If the pointer is always valid, any load with first index 0 is valid.
if (isByValOrInAlloca || AllCallersPassInValidPointerForArgument(Arg))
SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
// First, iterate the entry block and mark loads of (geps of) arguments as
// safe.
BasicBlock &EntryBlock = Arg->getParent()->front();
// Declare this here so we can reuse it
IndicesVector Indices;
for (Instruction &I : EntryBlock)
if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
Value *V = LI->getPointerOperand();
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
V = GEP->getPointerOperand();
if (V == Arg) {
// This load actually loads (part of) Arg? Check the indices then.
Indices.reserve(GEP->getNumIndices());
for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
II != IE; ++II)
if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
Indices.push_back(CI->getSExtValue());
else
// We found a non-constant GEP index for this argument? Bail out
// right away, can't promote this argument at all.
return false;
// Indices checked out, mark them as safe
MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
Indices.clear();
}
} else if (V == Arg) {
// Direct loads are equivalent to a GEP with a single 0 index.
MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
}
}
// Now, iterate all uses of the argument to see if there are any uses that are
// not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
SmallVector<LoadInst*, 16> Loads;
IndicesVector Operands;
for (Use &U : Arg->uses()) {
User *UR = U.getUser();
Operands.clear();
if (LoadInst *LI = dyn_cast<LoadInst>(UR)) {
// Don't hack volatile/atomic loads
if (!LI->isSimple()) return false;
Loads.push_back(LI);
// Direct loads are equivalent to a GEP with a zero index and then a load.
Operands.push_back(0);
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UR)) {
if (GEP->use_empty()) {
// Dead GEP's cause trouble later. Just remove them if we run into
// them.
GEP->eraseFromParent();
// TODO: This runs the above loop over and over again for dead GEPs
// Couldn't we just do increment the UI iterator earlier and erase the
// use?
return isSafeToPromoteArgument(Arg, isByValOrInAlloca, AAR);
}
// Ensure that all of the indices are constants.
for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
i != e; ++i)
if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
Operands.push_back(C->getSExtValue());
else
return false; // Not a constant operand GEP!
// Ensure that the only users of the GEP are load instructions.
for (User *GEPU : GEP->users())
if (LoadInst *LI = dyn_cast<LoadInst>(GEPU)) {
// Don't hack volatile/atomic loads
if (!LI->isSimple()) return false;
Loads.push_back(LI);
} else {
// Other uses than load?
return false;
}
} else {
return false; // Not a load or a GEP.
}
// Now, see if it is safe to promote this load / loads of this GEP. Loading
// is safe if Operands, or a prefix of Operands, is marked as safe.
if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
return false;
// See if we are already promoting a load with these indices. If not, check
// to make sure that we aren't promoting too many elements. If so, nothing
// to do.
if (ToPromote.find(Operands) == ToPromote.end()) {
if (maxElements > 0 && ToPromote.size() == maxElements) {
DEBUG(dbgs() << "argpromotion not promoting argument '"
<< Arg->getName() << "' because it would require adding more "
<< "than " << maxElements << " arguments to the function.\n");
// We limit aggregate promotion to only promoting up to a fixed number
// of elements of the aggregate.
return false;
}
ToPromote.insert(std::move(Operands));
}
}
if (Loads.empty()) return true; // No users, this is a dead argument.
// Okay, now we know that the argument is only used by load instructions and
// it is safe to unconditionally perform all of them. Use alias analysis to
// check to see if the pointer is guaranteed to not be modified from entry of
// the function to each of the load instructions.
// Because there could be several/many load instructions, remember which
// blocks we know to be transparent to the load.
SmallPtrSet<BasicBlock*, 16> TranspBlocks;
for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
// Check to see if the load is invalidated from the start of the block to
// the load itself.
LoadInst *Load = Loads[i];
BasicBlock *BB = Load->getParent();
MemoryLocation Loc = MemoryLocation::get(Load);
if (AAR.canInstructionRangeModRef(BB->front(), *Load, Loc, MRI_Mod))
return false; // Pointer is invalidated!
// Now check every path from the entry block to the load for transparency.
// To do this, we perform a depth first search on the inverse CFG from the
// loading block.
for (BasicBlock *P : predecessors(BB)) {
for (BasicBlock *TranspBB : inverse_depth_first_ext(P, TranspBlocks))
if (AAR.canBasicBlockModify(*TranspBB, Loc))
return false;
}
}
// If the path from the entry of the function to each load is free of
// instructions that potentially invalidate the load, we can make the
// transformation!
return true;
}
void AAEvaluator::runInternal(Function &F, AAResults &AA) {
const DataLayout &DL = F.getParent()->getDataLayout();
++FunctionCount;
SetVector<Value *> Pointers;
SmallSetVector<CallBase *, 16> Calls;
SetVector<Value *> Loads;
SetVector<Value *> Stores;
for (auto &I : F.args())
if (I.getType()->isPointerTy()) // Add all pointer arguments.
Pointers.insert(&I);
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
if (I->getType()->isPointerTy()) // Add all pointer instructions.
Pointers.insert(&*I);
if (EvalAAMD && isa<LoadInst>(&*I))
Loads.insert(&*I);
if (EvalAAMD && isa<StoreInst>(&*I))
Stores.insert(&*I);
Instruction &Inst = *I;
if (auto *Call = dyn_cast<CallBase>(&Inst)) {
Value *Callee = Call->getCalledValue();
// Skip actual functions for direct function calls.
if (!isa<Function>(Callee) && isInterestingPointer(Callee))
Pointers.insert(Callee);
// Consider formals.
for (Use &DataOp : Call->data_ops())
if (isInterestingPointer(DataOp))
Pointers.insert(DataOp);
Calls.insert(Call);
} else {
// Consider all operands.
for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
OI != OE; ++OI)
if (isInterestingPointer(*OI))
Pointers.insert(*OI);
}
}
if (PrintAll || PrintNoAlias || PrintMayAlias || PrintPartialAlias ||
PrintMustAlias || PrintNoModRef || PrintMod || PrintRef || PrintModRef)
errs() << "Function: " << F.getName() << ": " << Pointers.size()
<< " pointers, " << Calls.size() << " call sites\n";
// iterate over the worklist, and run the full (n^2)/2 disambiguations
for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
I1 != E; ++I1) {
auto I1Size = LocationSize::unknown();
Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
if (I1ElTy->isSized())
I1Size = LocationSize::precise(DL.getTypeStoreSize(I1ElTy));
for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
auto I2Size = LocationSize::unknown();
Type *I2ElTy = cast<PointerType>((*I2)->getType())->getElementType();
if (I2ElTy->isSized())
I2Size = LocationSize::precise(DL.getTypeStoreSize(I2ElTy));
AliasResult AR = AA.alias(*I1, I1Size, *I2, I2Size);
switch (AR) {
case NoAlias:
PrintResults(AR, PrintNoAlias, *I1, *I2, F.getParent());
++NoAliasCount;
break;
case MayAlias:
PrintResults(AR, PrintMayAlias, *I1, *I2, F.getParent());
++MayAliasCount;
break;
case PartialAlias:
PrintResults(AR, PrintPartialAlias, *I1, *I2, F.getParent());
++PartialAliasCount;
break;
case MustAlias:
PrintResults(AR, PrintMustAlias, *I1, *I2, F.getParent());
++MustAliasCount;
break;
}
}
}
if (EvalAAMD) {
// iterate over all pairs of load, store
for (Value *Load : Loads) {
for (Value *Store : Stores) {
AliasResult AR = AA.alias(MemoryLocation::get(cast<LoadInst>(Load)),
MemoryLocation::get(cast<StoreInst>(Store)));
switch (AR) {
case NoAlias:
PrintLoadStoreResults(AR, PrintNoAlias, Load, Store, F.getParent());
++NoAliasCount;
break;
case MayAlias:
PrintLoadStoreResults(AR, PrintMayAlias, Load, Store, F.getParent());
++MayAliasCount;
break;
case PartialAlias:
PrintLoadStoreResults(AR, PrintPartialAlias, Load, Store, F.getParent());
++PartialAliasCount;
break;
case MustAlias:
PrintLoadStoreResults(AR, PrintMustAlias, Load, Store, F.getParent());
++MustAliasCount;
break;
}
}
}
// iterate over all pairs of store, store
for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
I1 != E; ++I1) {
for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
AliasResult AR = AA.alias(MemoryLocation::get(cast<StoreInst>(*I1)),
MemoryLocation::get(cast<StoreInst>(*I2)));
switch (AR) {
case NoAlias:
PrintLoadStoreResults(AR, PrintNoAlias, *I1, *I2, F.getParent());
++NoAliasCount;
break;
case MayAlias:
PrintLoadStoreResults(AR, PrintMayAlias, *I1, *I2, F.getParent());
++MayAliasCount;
break;
case PartialAlias:
PrintLoadStoreResults(AR, PrintPartialAlias, *I1, *I2, F.getParent());
++PartialAliasCount;
break;
case MustAlias:
PrintLoadStoreResults(AR, PrintMustAlias, *I1, *I2, F.getParent());
++MustAliasCount;
break;
}
}
}
}
// Mod/ref alias analysis: compare all pairs of calls and values
for (CallBase *Call : Calls) {
for (auto Pointer : Pointers) {
auto Size = LocationSize::unknown();
Type *ElTy = cast<PointerType>(Pointer->getType())->getElementType();
if (ElTy->isSized())
Size = LocationSize::precise(DL.getTypeStoreSize(ElTy));
switch (AA.getModRefInfo(Call, Pointer, Size)) {
case ModRefInfo::NoModRef:
PrintModRefResults("NoModRef", PrintNoModRef, Call, Pointer,
F.getParent());
++NoModRefCount;
break;
case ModRefInfo::Mod:
PrintModRefResults("Just Mod", PrintMod, Call, Pointer, F.getParent());
++ModCount;
break;
case ModRefInfo::Ref:
PrintModRefResults("Just Ref", PrintRef, Call, Pointer, F.getParent());
++RefCount;
break;
case ModRefInfo::ModRef:
PrintModRefResults("Both ModRef", PrintModRef, Call, Pointer,
F.getParent());
++ModRefCount;
break;
case ModRefInfo::Must:
PrintModRefResults("Must", PrintMust, Call, Pointer, F.getParent());
++MustCount;
break;
case ModRefInfo::MustMod:
PrintModRefResults("Just Mod (MustAlias)", PrintMustMod, Call, Pointer,
F.getParent());
++MustModCount;
break;
case ModRefInfo::MustRef:
PrintModRefResults("Just Ref (MustAlias)", PrintMustRef, Call, Pointer,
F.getParent());
++MustRefCount;
break;
case ModRefInfo::MustModRef:
PrintModRefResults("Both ModRef (MustAlias)", PrintMustModRef, Call,
Pointer, F.getParent());
++MustModRefCount;
break;
}
}
}
// Mod/ref alias analysis: compare all pairs of calls
for (CallBase *CallA : Calls) {
for (CallBase *CallB : Calls) {
if (CallA == CallB)
continue;
switch (AA.getModRefInfo(CallA, CallB)) {
case ModRefInfo::NoModRef:
PrintModRefResults("NoModRef", PrintNoModRef, CallA, CallB,
F.getParent());
++NoModRefCount;
break;
case ModRefInfo::Mod:
PrintModRefResults("Just Mod", PrintMod, CallA, CallB, F.getParent());
++ModCount;
break;
case ModRefInfo::Ref:
PrintModRefResults("Just Ref", PrintRef, CallA, CallB, F.getParent());
++RefCount;
break;
case ModRefInfo::ModRef:
PrintModRefResults("Both ModRef", PrintModRef, CallA, CallB,
F.getParent());
++ModRefCount;
break;
case ModRefInfo::Must:
PrintModRefResults("Must", PrintMust, CallA, CallB, F.getParent());
++MustCount;
break;
case ModRefInfo::MustMod:
PrintModRefResults("Just Mod (MustAlias)", PrintMustMod, CallA, CallB,
F.getParent());
++MustModCount;
break;
case ModRefInfo::MustRef:
PrintModRefResults("Just Ref (MustAlias)", PrintMustRef, CallA, CallB,
F.getParent());
++MustRefCount;
break;
case ModRefInfo::MustModRef:
PrintModRefResults("Both ModRef (MustAlias)", PrintMustModRef, CallA,
CallB, F.getParent());
++MustModRefCount;
break;
}
}
}
}
TestAnalyses(MemorySSATest &Test)
: DT(*Test.F), AC(*Test.F), AA(Test.TLI),
BAA(Test.DL, Test.TLI, AC, &DT), MSSA(*Test.F) {
AA.addAAResult(BAA);
Walker.reset(MSSA.buildMemorySSA(&AA, &DT));
}
