mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-26 23:29:22 +00:00
remove the "undead" terminology, which is nonstandard and never
made sense to me. We now have a set of dead stack objects, and they become live when loaded. Fix a theoretical problem where we'd pass in the wrong pointer to the alias query. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120465 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
86dc6c08cf
commit
5fb0fb397c
@ -64,9 +64,9 @@ namespace {
|
||||
bool runOnBasicBlock(BasicBlock &BB);
|
||||
bool HandleFree(CallInst *F);
|
||||
bool handleEndBlock(BasicBlock &BB);
|
||||
bool RemoveUndeadPointers(Value *Ptr, uint64_t killPointerSize,
|
||||
BasicBlock::iterator &BBI,
|
||||
SmallPtrSet<Value*, 16> &deadPointers);
|
||||
bool RemoveAccessedObjects(Value *Ptr, uint64_t killPointerSize,
|
||||
BasicBlock::iterator &BBI,
|
||||
SmallPtrSet<Value*, 16> &deadPointers);
|
||||
void DeleteDeadInstruction(Instruction *I,
|
||||
SmallPtrSet<Value*, 16> *deadPointers = 0);
|
||||
|
||||
@ -399,21 +399,22 @@ bool DSE::HandleFree(CallInst *F) {
|
||||
bool DSE::handleEndBlock(BasicBlock &BB) {
|
||||
bool MadeChange = false;
|
||||
|
||||
// Pointers alloca'd in this function are dead in the end block
|
||||
SmallPtrSet<Value*, 16> DeadPointers;
|
||||
// Keep track of all of the stack objects that are dead at the end of the
|
||||
// function.
|
||||
SmallPtrSet<Value*, 16> DeadStackObjects;
|
||||
|
||||
// Find all of the alloca'd pointers in the entry block.
|
||||
BasicBlock *Entry = BB.getParent()->begin();
|
||||
for (BasicBlock::iterator I = Entry->begin(), E = Entry->end(); I != E; ++I)
|
||||
if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
|
||||
DeadPointers.insert(AI);
|
||||
DeadStackObjects.insert(AI);
|
||||
|
||||
// Treat byval arguments the same, stores to them are dead at the end of the
|
||||
// function.
|
||||
for (Function::arg_iterator AI = BB.getParent()->arg_begin(),
|
||||
AE = BB.getParent()->arg_end(); AI != AE; ++AI)
|
||||
if (AI->hasByValAttr())
|
||||
DeadPointers.insert(AI);
|
||||
DeadStackObjects.insert(AI);
|
||||
|
||||
// Scan the basic block backwards
|
||||
for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
|
||||
@ -426,10 +427,10 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
|
||||
|
||||
// Alloca'd pointers or byval arguments (which are functionally like
|
||||
// alloca's) are valid candidates for removal.
|
||||
if (DeadPointers.count(Pointer)) {
|
||||
if (DeadStackObjects.count(Pointer)) {
|
||||
// DCE instructions only used to calculate that store.
|
||||
Instruction *Dead = BBI++;
|
||||
DeleteDeadInstruction(Dead, &DeadPointers);
|
||||
DeleteDeadInstruction(Dead, &DeadStackObjects);
|
||||
++NumFastStores;
|
||||
MadeChange = true;
|
||||
continue;
|
||||
@ -439,14 +440,14 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
|
||||
// Remove any dead non-memory-mutating instructions.
|
||||
if (isInstructionTriviallyDead(BBI)) {
|
||||
Instruction *Inst = BBI++;
|
||||
DeleteDeadInstruction(Inst, &DeadPointers);
|
||||
DeleteDeadInstruction(Inst, &DeadStackObjects);
|
||||
++NumFastOther;
|
||||
MadeChange = true;
|
||||
continue;
|
||||
}
|
||||
|
||||
if (AllocaInst *A = dyn_cast<AllocaInst>(BBI)) {
|
||||
DeadPointers.erase(A);
|
||||
DeadStackObjects.erase(A);
|
||||
continue;
|
||||
}
|
||||
|
||||
@ -461,8 +462,8 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
|
||||
// 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) {
|
||||
for (SmallPtrSet<Value*, 16>::iterator I = DeadStackObjects.begin(),
|
||||
E = DeadStackObjects.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.
|
||||
@ -484,11 +485,11 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
|
||||
|
||||
for (SmallVector<Value*, 8>::iterator I = LiveAllocas.begin(),
|
||||
E = LiveAllocas.end(); I != E; ++I)
|
||||
DeadPointers.erase(*I);
|
||||
DeadStackObjects.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())
|
||||
if (DeadStackObjects.empty())
|
||||
return MadeChange;
|
||||
|
||||
continue;
|
||||
@ -511,41 +512,47 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
|
||||
continue;
|
||||
}
|
||||
|
||||
KillPointer = KillPointer->getUnderlyingObject();
|
||||
// Remove any allocas from the DeadPointer set that are loaded, as this
|
||||
// makes any stores above the access live.
|
||||
MadeChange |= RemoveAccessedObjects(KillPointer, KillPointerSize, BBI,
|
||||
DeadStackObjects);
|
||||
|
||||
// Deal with undead pointers
|
||||
MadeChange |= RemoveUndeadPointers(KillPointer, KillPointerSize, BBI,
|
||||
DeadPointers);
|
||||
// If all of the allocas were clobbered by the access then we're not going
|
||||
// to find anything else to process.
|
||||
if (DeadStackObjects.empty())
|
||||
break;
|
||||
}
|
||||
|
||||
return MadeChange;
|
||||
}
|
||||
|
||||
/// RemoveUndeadPointers - check for uses of a pointer that make it
|
||||
/// undead when scanning for dead stores to alloca's.
|
||||
bool DSE::RemoveUndeadPointers(Value *killPointer, uint64_t killPointerSize,
|
||||
BasicBlock::iterator &BBI,
|
||||
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)) {
|
||||
DeadPointers.erase(killPointer);
|
||||
/// RemoveAccessedObjects - Check to see if the specified location may alias any
|
||||
/// of the stack objects in the DeadStackObjects set. If so, they become live
|
||||
/// because the location is being loaded.
|
||||
bool DSE::RemoveAccessedObjects(Value *KillPointer, uint64_t KillPointerSize,
|
||||
BasicBlock::iterator &BBI,
|
||||
SmallPtrSet<Value*, 16> &DeadStackObjects) {
|
||||
Value *UnderlyingPointer = KillPointer->getUnderlyingObject();
|
||||
|
||||
// A constant can't be in the dead pointer set.
|
||||
if (isa<Constant>(UnderlyingPointer))
|
||||
return false;
|
||||
|
||||
// If the kill pointer can be easily reduced to an alloca, don't bother doing
|
||||
// extraneous AA queries.
|
||||
if (DeadStackObjects.count(UnderlyingPointer)) {
|
||||
DeadStackObjects.erase(UnderlyingPointer);
|
||||
return false;
|
||||
}
|
||||
|
||||
// A global can't be in the dead pointer set.
|
||||
if (isa<GlobalValue>(killPointer))
|
||||
return false;
|
||||
|
||||
bool MadeChange = false;
|
||||
SmallVector<Value*, 16> NowLive;
|
||||
|
||||
SmallVector<Value*, 16> undead;
|
||||
|
||||
for (SmallPtrSet<Value*, 64>::iterator I = DeadPointers.begin(),
|
||||
E = DeadPointers.end(); I != E; ++I) {
|
||||
for (SmallPtrSet<Value*, 16>::iterator I = DeadStackObjects.begin(),
|
||||
E = DeadStackObjects.end(); I != E; ++I) {
|
||||
// See if this pointer could alias it
|
||||
AliasAnalysis::AliasResult A = AA->alias(*I, getPointerSize(*I, *AA),
|
||||
killPointer, killPointerSize);
|
||||
KillPointer, KillPointerSize);
|
||||
|
||||
// If it must-alias and a store, we can delete it
|
||||
if (isa<StoreInst>(BBI) && A == AliasAnalysis::MustAlias) {
|
||||
@ -553,7 +560,7 @@ bool DSE::RemoveUndeadPointers(Value *killPointer, uint64_t killPointerSize,
|
||||
|
||||
// Remove it!
|
||||
++BBI;
|
||||
DeleteDeadInstruction(S, &DeadPointers);
|
||||
DeleteDeadInstruction(S, &DeadStackObjects);
|
||||
++NumFastStores;
|
||||
MadeChange = true;
|
||||
|
||||
@ -561,12 +568,12 @@ bool DSE::RemoveUndeadPointers(Value *killPointer, uint64_t killPointerSize,
|
||||
|
||||
// Otherwise, it is undead
|
||||
} else if (A != AliasAnalysis::NoAlias)
|
||||
undead.push_back(*I);
|
||||
NowLive.push_back(*I);
|
||||
}
|
||||
|
||||
for (SmallVector<Value*, 16>::iterator I = undead.begin(), E = undead.end();
|
||||
for (SmallVector<Value*, 16>::iterator I = NowLive.begin(), E = NowLive.end();
|
||||
I != E; ++I)
|
||||
DeadPointers.erase(*I);
|
||||
DeadStackObjects.erase(*I);
|
||||
|
||||
return MadeChange;
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user