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move call handling in handleEndBlock up a bit, and simplify it.

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If the call might read all the allocas, stop scanning early.
Convert a vector to smallvector, shrink SmallPtrSet to 16 instead
of 64 to avoid crazy linear scans.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120463 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-11-30 21:18:46 +00:00
parent 75627d3d2e
commit 86dc6c08cf
1 changed files with 48 additions and 45 deletions
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93
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -66,9 +66,9 @@ namespace {
bool handleEndBlock(BasicBlock &BB);
bool RemoveUndeadPointers(Value *Ptr, uint64_t killPointerSize,
BasicBlock::iterator &BBI,
SmallPtrSet<Value*, 64> &deadPointers);
SmallPtrSet<Value*, 16> &deadPointers);
void DeleteDeadInstruction(Instruction *I,
SmallPtrSet<Value*, 64> *deadPointers = 0);
SmallPtrSet<Value*, 16> *deadPointers = 0);
// getAnalysisUsage - We require post dominance frontiers (aka Control
@ -400,7 +400,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
bool MadeChange = false;
// Pointers alloca'd in this function are dead in the end block
SmallPtrSet<Value*, 64> DeadPointers;
SmallPtrSet<Value*, 16> DeadPointers;
// Find all of the alloca'd pointers in the entry block.
BasicBlock *Entry = BB.getParent()->begin();
@ -450,6 +450,49 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
continue;
}
if (CallSite CS = cast<Value>(BBI)) {
// If this call does not access memory, it can't be loading any of our
// pointers.
if (AA->doesNotAccessMemory(CS))
continue;
unsigned NumModRef = 0, NumOther = 0;
// If the call might load from any of our allocas, then any store above
// the call is live.
SmallVector<Value*, 8> LiveAllocas;
for (SmallPtrSet<Value*, 16>::iterator I = DeadPointers.begin(),
E = DeadPointers.end(); I != E; ++I) {
// If we detect that our AA is imprecise, it's not worth it to scan the
// rest of the DeadPointers set. Just assume that the AA will return
// ModRef for everything, and go ahead and bail out.
if (NumModRef >= 16 && NumOther == 0)
return MadeChange;
// See if the call site touches it.
AliasAnalysis::ModRefResult A =
AA->getModRefInfo(CS, *I, getPointerSize(*I, *AA));
if (A == AliasAnalysis::ModRef)
++NumModRef;
else
++NumOther;
if (A == AliasAnalysis::ModRef || A == AliasAnalysis::Ref)
LiveAllocas.push_back(*I);
}
for (SmallVector<Value*, 8>::iterator I = LiveAllocas.begin(),
E = LiveAllocas.end(); I != E; ++I)
DeadPointers.erase(*I);
// If all of the allocas were clobbered by the call then we're not going
// to find anything else to process.
if (DeadPointers.empty())
return MadeChange;
continue;
}
Value *KillPointer = 0;
uint64_t KillPointerSize = AliasAnalysis::UnknownSize;
@ -463,46 +506,6 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
KillPointer = cast<MemTransferInst>(BBI)->getSource();
if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
KillPointerSize = Len->getZExtValue();
} else if (CallSite CS = cast<Value>(BBI)) {
// If this call does not access memory, it can't be loading any of our
// pointers.
if (AA->doesNotAccessMemory(CS))
continue;
unsigned NumModRef = 0;
unsigned NumOther = 0;
// Remove any pointers made undead by the call from the dead set
std::vector<Value*> dead;
for (SmallPtrSet<Value*, 64>::iterator I = DeadPointers.begin(),
E = DeadPointers.end(); I != E; ++I) {
// HACK: if we detect that our AA is imprecise, it's not
// worth it to scan the rest of the deadPointers set. Just
// assume that the AA will return ModRef for everything, and
// go ahead and bail.
if (NumModRef >= 16 && NumOther == 0) {
DeadPointers.clear();
return MadeChange;
}
// See if the call site touches it
AliasAnalysis::ModRefResult A =
AA->getModRefInfo(CS, *I, getPointerSize(*I, *AA));
if (A == AliasAnalysis::ModRef)
++NumModRef;
else
++NumOther;
if (A == AliasAnalysis::ModRef || A == AliasAnalysis::Ref)
dead.push_back(*I);
}
for (std::vector<Value*>::iterator I = dead.begin(), E = dead.end();
I != E; ++I)
DeadPointers.erase(*I);
continue;
} else {
// Not a loading instruction.
continue;
@ -522,7 +525,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
/// undead when scanning for dead stores to alloca's.
bool DSE::RemoveUndeadPointers(Value *killPointer, uint64_t killPointerSize,
BasicBlock::iterator &BBI,
SmallPtrSet<Value*, 64> &DeadPointers) {
SmallPtrSet<Value*, 16> &DeadPointers) {
// If the kill pointer can be easily reduced to an alloca,
// don't bother doing extraneous AA queries.
if (DeadPointers.count(killPointer)) {
@ -575,7 +578,7 @@ bool DSE::RemoveUndeadPointers(Value *killPointer, uint64_t killPointerSize,
/// If ValueSet is non-null, remove any deleted instructions from it as well.
///
void DSE::DeleteDeadInstruction(Instruction *I,
SmallPtrSet<Value*, 64> *ValueSet) {
SmallPtrSet<Value*, 16> *ValueSet) {
SmallVector<Instruction*, 32> NowDeadInsts;
NowDeadInsts.push_back(I);