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[ObjC][ARC] Add and use a function which finds and returns the single

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dependency. NFC

Use findSingleDependency in place of FindDependencies and stop passing a
set of Instructions around. Modify FindDependencies to return a boolean
flag which indicates whether the dependencies it has found are all
valid.
This commit is contained in:
Akira Hatanaka 2020-11-13 10:40:40 -08:00
parent c9d70c3f7d
commit 05f0b5f315
4 changed files with 64 additions and 82 deletions
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48
lib/Transforms/ObjCARC/DependencyAnalysis.cpp
View File

@ -208,12 +208,10 @@ llvm::objcarc::Depends(DependenceKind Flavor, Instruction *Inst,
/// non-local dependencies on Arg.
///
/// TODO: Cache results?
void
llvm::objcarc::FindDependencies(DependenceKind Flavor,
const Value *Arg,
BasicBlock *StartBB, Instruction *StartInst,
SmallPtrSetImpl<Instruction *> &DependingInsts,
ProvenanceAnalysis &PA) {
static bool findDependencies(DependenceKind Flavor, const Value *Arg,
BasicBlock *StartBB, Instruction *StartInst,
SmallPtrSetImpl<Instruction *> &DependingInsts,
ProvenanceAnalysis &PA) {
BasicBlock::iterator StartPos = StartInst->getIterator();
SmallPtrSet<const BasicBlock *, 4> Visited;
@ -229,15 +227,14 @@ llvm::objcarc::FindDependencies(DependenceKind Flavor,
if (LocalStartPos == StartBBBegin) {
pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
if (PI == PE)
// If we've reached the function entry, produce a null dependence.
DependingInsts.insert(nullptr);
else
// Add the predecessors to the worklist.
do {
BasicBlock *PredBB = *PI;
if (Visited.insert(PredBB).second)
Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
} while (++PI != PE);
// Return if we've reached the function entry.
return false;
// Add the predecessors to the worklist.
do {
BasicBlock *PredBB = *PI;
if (Visited.insert(PredBB).second)
Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
} while (++PI != PE);
break;
}
@ -256,9 +253,22 @@ llvm::objcarc::FindDependencies(DependenceKind Flavor,
if (BB == StartBB)
continue;
for (const BasicBlock *Succ : successors(BB))
if (Succ != StartBB && !Visited.count(Succ)) {
DependingInsts.insert(reinterpret_cast<Instruction *>(-1));
return;
}
if (Succ != StartBB && !Visited.count(Succ))
return false;
}
return true;
}
llvm::Instruction *llvm::objcarc::findSingleDependency(DependenceKind Flavor,
const Value *Arg,
BasicBlock *StartBB,
Instruction *StartInst,
ProvenanceAnalysis &PA) {
SmallPtrSet<Instruction *, 4> DependingInsts;
if (!findDependencies(Flavor, Arg, StartBB, StartInst, DependingInsts, PA) ||
DependingInsts.size() != 1)
return nullptr;
return *DependingInsts.begin();
}

11
lib/Transforms/ObjCARC/DependencyAnalysis.h
View File

@ -50,11 +50,12 @@ enum DependenceKind {
RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
};
void FindDependencies(DependenceKind Flavor,
const Value *Arg,
BasicBlock *StartBB, Instruction *StartInst,
SmallPtrSetImpl<Instruction *> &DependingInstructions,
ProvenanceAnalysis &PA);
/// Find dependent instructions. If there is exactly one dependent instruction,
/// return it. Otherwise, return null.
llvm::Instruction *findSingleDependency(DependenceKind Flavor, const Value *Arg,
BasicBlock *StartBB,
Instruction *StartInst,
ProvenanceAnalysis &PA);
bool
Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,

19
lib/Transforms/ObjCARC/ObjCARCContract.cpp
View File

@ -161,20 +161,11 @@ bool ObjCARCContract::contractAutorelease(Function &F, Instruction *Autorelease,
// Check that there are no instructions between the retain and the autorelease
// (such as an autorelease_pop) which may change the count.
CallInst *Retain = nullptr;
SmallPtrSet<Instruction *, 4> DependingInstructions;
if (Class == ARCInstKind::AutoreleaseRV)
FindDependencies(RetainAutoreleaseRVDep, Arg, Autorelease->getParent(),
Autorelease, DependingInstructions, PA);
else
FindDependencies(RetainAutoreleaseDep, Arg, Autorelease->getParent(),
Autorelease, DependingInstructions, PA);
if (DependingInstructions.size() != 1)
return false;
Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
DependenceKind DK = Class == ARCInstKind::AutoreleaseRV
? RetainAutoreleaseRVDep
: RetainAutoreleaseDep;
auto *Retain = dyn_cast_or_null<CallInst>(
findSingleDependency(DK, Arg, Autorelease->getParent(), Autorelease, PA));
if (!Retain || GetBasicARCInstKind(Retain) != ARCInstKind::Retain ||
GetArgRCIdentityRoot(Retain) != Arg)

68
lib/Transforms/ObjCARC/ObjCARCOpts.cpp
View File

@ -1125,7 +1125,7 @@ void ObjCARCOpt::OptimizeIndividualCallImpl(
if (!HasNull)
continue;
SmallPtrSet<Instruction *, 4> DependingInstructions;
Instruction *DepInst = nullptr;
// Check that there is nothing that cares about the reference
// count between the call and the phi.
@ -1137,13 +1137,13 @@ void ObjCARCOpt::OptimizeIndividualCallImpl(
case ARCInstKind::Release:
// These can't be moved across things that care about the retain
// count.
FindDependencies(NeedsPositiveRetainCount, Arg, Inst->getParent(), Inst,
DependingInstructions, PA);
DepInst = findSingleDependency(NeedsPositiveRetainCount, Arg,
Inst->getParent(), Inst, PA);
break;
case ARCInstKind::Autorelease:
// These can't be moved across autorelease pool scope boundaries.
FindDependencies(AutoreleasePoolBoundary, Arg, Inst->getParent(), Inst,
DependingInstructions, PA);
DepInst = findSingleDependency(AutoreleasePoolBoundary, Arg,
Inst->getParent(), Inst, PA);
break;
case ARCInstKind::ClaimRV:
case ARCInstKind::RetainRV:
@ -1157,9 +1157,7 @@ void ObjCARCOpt::OptimizeIndividualCallImpl(
llvm_unreachable("Invalid dependence flavor");
}
if (DependingInstructions.size() != 1)
continue;
if (*DependingInstructions.begin() != PN)
if (DepInst != PN)
continue;
Changed = true;
@ -2233,24 +2231,21 @@ bool ObjCARCOpt::OptimizeSequences(Function &F) {
/// Check if there is a dependent call earlier that does not have anything in
/// between the Retain and the call that can affect the reference count of their
/// shared pointer argument. Note that Retain need not be in BB.
static bool
HasSafePathToPredecessorCall(const Value *Arg, Instruction *Retain,
SmallPtrSetImpl<Instruction *> &DepInsts,
ProvenanceAnalysis &PA) {
FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
DepInsts, PA);
if (DepInsts.size() != 1)
return false;
auto *Call = dyn_cast_or_null<CallInst>(*DepInsts.begin());
static CallInst *HasSafePathToPredecessorCall(const Value *Arg,
Instruction *Retain,
ProvenanceAnalysis &PA) {
auto *Call = dyn_cast_or_null<CallInst>(findSingleDependency(
CanChangeRetainCount, Arg, Retain->getParent(), Retain, PA));
// Check that the pointer is the return value of the call.
if (!Call || Arg != Call)
return false;
return nullptr;
// Check that the call is a regular call.
ARCInstKind Class = GetBasicARCInstKind(Call);
return Class == ARCInstKind::CallOrUser || Class == ARCInstKind::Call;
return Class == ARCInstKind::CallOrUser || Class == ARCInstKind::Call
? Call
: nullptr;
}
/// Find a dependent retain that precedes the given autorelease for which there
@ -2260,12 +2255,8 @@ static CallInst *
FindPredecessorRetainWithSafePath(const Value *Arg, BasicBlock *BB,
Instruction *Autorelease,
ProvenanceAnalysis &PA) {
SmallPtrSet<Instruction *, 4> DepInsts;
FindDependencies(CanChangeRetainCount, Arg, BB, Autorelease, DepInsts, PA);
if (DepInsts.size() != 1)
return nullptr;
auto *Retain = dyn_cast_or_null<CallInst>(*DepInsts.begin());
auto *Retain = dyn_cast_or_null<CallInst>(
findSingleDependency(CanChangeRetainCount, Arg, BB, Autorelease, PA));
// Check that we found a retain with the same argument.
if (!Retain || !IsRetain(GetBasicARCInstKind(Retain)) ||
@ -2284,11 +2275,9 @@ FindPredecessorAutoreleaseWithSafePath(const Value *Arg, BasicBlock *BB,
ReturnInst *Ret,
ProvenanceAnalysis &PA) {
SmallPtrSet<Instruction *, 4> DepInsts;
FindDependencies(NeedsPositiveRetainCount, Arg, BB, Ret, DepInsts, PA);
if (DepInsts.size() != 1)
return nullptr;
auto *Autorelease = dyn_cast_or_null<CallInst>(
findSingleDependency(NeedsPositiveRetainCount, Arg, BB, Ret, PA));
auto *Autorelease = dyn_cast_or_null<CallInst>(*DepInsts.begin());
if (!Autorelease)
return nullptr;
ARCInstKind AutoreleaseClass = GetBasicARCInstKind(Autorelease);
@ -2314,7 +2303,6 @@ void ObjCARCOpt::OptimizeReturns(Function &F) {
LLVM_DEBUG(dbgs() << "\n== ObjCARCOpt::OptimizeReturns ==\n");
SmallPtrSet<Instruction *, 4> DependingInstructions;
for (BasicBlock &BB: F) {
ReturnInst *Ret = dyn_cast<ReturnInst>(&BB.back());
if (!Ret)
@ -2341,21 +2329,13 @@ void ObjCARCOpt::OptimizeReturns(Function &F) {
// Check that there is nothing that can affect the reference count
// between the retain and the call. Note that Retain need not be in BB.
bool HasSafePathToCall =
HasSafePathToPredecessorCall(Arg, Retain, DependingInstructions, PA);
CallInst *Call = HasSafePathToPredecessorCall(Arg, Retain, PA);
// Don't remove retainRV/autoreleaseRV pairs if the call isn't a tail call.
if (HasSafePathToCall &&
GetBasicARCInstKind(Retain) == ARCInstKind::RetainRV &&
GetBasicARCInstKind(Autorelease) == ARCInstKind::AutoreleaseRV &&
!cast<CallInst>(*DependingInstructions.begin())->isTailCall()) {
DependingInstructions.clear();
continue;
}
DependingInstructions.clear();
if (!HasSafePathToCall)
if (!Call ||
(!Call->isTailCall() &&
GetBasicARCInstKind(Retain) == ARCInstKind::RetainRV &&
GetBasicARCInstKind(Autorelease) == ARCInstKind::AutoreleaseRV))
continue;
// If so, we can zap the retain and autorelease.