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Add some comments, remove a dead argument, and simplify some control flow.

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No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40932 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2007-08-08 17:50:09 +00:00
parent 79e038a16d
commit bb3abf41a8
1 changed files with 28 additions and 19 deletions
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47
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -51,9 +51,9 @@ namespace {
Instruction* dependency,
SetVector<Instruction*>& possiblyDead);
bool handleEndBlock(BasicBlock& BB, SetVector<Instruction*>& possiblyDead);
bool RemoveUndeadPointers(Value* pointer, unsigned pointerSize,
bool RemoveUndeadPointers(Value* pointer,
BasicBlock::iterator& BBI,
SmallPtrSet<AllocaInst*, 4>& deadPointers,
SmallPtrSet<AllocaInst*, 64>& deadPointers,
SetVector<Instruction*>& possiblyDead);
void DeleteDeadInstructionChains(Instruction *I,
SetVector<Instruction*> &DeadInsts);
@ -222,7 +222,11 @@ bool DSE::handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dep,
}
/// handleEndBlock - Remove dead stores to stack-allocated locations in the
/// function end block
/// function end block. Ex:
/// %A = alloca i32
/// ...
/// store i32 1, i32* %A
/// ret void
bool DSE::handleEndBlock(BasicBlock& BB,
SetVector<Instruction*>& possiblyDead) {
TargetData &TD = getAnalysis<TargetData>();
@ -232,7 +236,7 @@ bool DSE::handleEndBlock(BasicBlock& BB,
bool MadeChange = false;
// Pointers alloca'd in this function are dead in the end block
SmallPtrSet<AllocaInst*, 4> deadPointers;
SmallPtrSet<AllocaInst*, 64> deadPointers;
// Find all of the alloca'd pointers in the entry block
BasicBlock *Entry = BB.getParent()->begin();
@ -247,9 +251,6 @@ bool DSE::handleEndBlock(BasicBlock& BB,
if (deadPointers.empty())
break;
Value* killPointer = 0;
unsigned killPointerSize = 0;
// If we find a store whose pointer is dead...
if (StoreInst* S = dyn_cast<StoreInst>(BBI)) {
Value* pointerOperand = S->getPointerOperand();
@ -271,24 +272,24 @@ bool DSE::handleEndBlock(BasicBlock& BB,
NumFastStores++;
MadeChange = true;
}
continue;
}
Value* killPointer = 0;
// If we encounter a use of the pointer, it is no longer considered dead
} else if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
killPointer = L->getPointerOperand();
killPointerSize = TD.getTypeSize(L->getType());
} else if (VAArgInst* V = dyn_cast<VAArgInst>(BBI)) {
killPointer = V->getOperand(0);
killPointerSize = TD.getTypeSize(V->getType());
} else if (FreeInst* F = dyn_cast<FreeInst>(BBI)) {
killPointer = F->getPointerOperand();
killPointerSize = ~0UL;
} else if (AllocaInst* A = dyn_cast<AllocaInst>(BBI)) {
deadPointers.erase(A);
continue;
} else if (CallSite::get(BBI).getInstruction() != 0) {
// Remove any pointers made undead by the call from the dead set
std::vector<Instruction*> dead;
for (SmallPtrSet<AllocaInst*, 4>::iterator I = deadPointers.begin(),
for (SmallPtrSet<AllocaInst*, 64>::iterator I = deadPointers.begin(),
E = deadPointers.end(); I != E; ++I) {
// Get size information for the alloca
unsigned pointerSize = ~0UL;
@ -314,16 +315,20 @@ bool DSE::handleEndBlock(BasicBlock& BB,
continue;
// Deal with undead pointers
MadeChange |= RemoveUndeadPointers(killPointer, killPointerSize, BBI,
MadeChange |= RemoveUndeadPointers(killPointer, BBI,
deadPointers, possiblyDead);
}
return MadeChange;
}
bool DSE::RemoveUndeadPointers(Value* killPointer, unsigned killPointerSize,
/// RemoveUndeadPointers - takes an instruction and a setvector of
/// dead instructions. If I is dead, it is erased, and its operands are
/// checked for deadness. If they are dead, they are added to the dead
/// setvector.
bool DSE::RemoveUndeadPointers(Value* killPointer,
BasicBlock::iterator& BBI,
SmallPtrSet<AllocaInst*, 4>& deadPointers,
SmallPtrSet<AllocaInst*, 64>& deadPointers,
SetVector<Instruction*>& possiblyDead) {
TargetData &TD = getAnalysis<TargetData>();
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
@ -333,7 +338,7 @@ bool DSE::RemoveUndeadPointers(Value* killPointer, unsigned killPointerSize,
std::vector<Instruction*> undead;
for (SmallPtrSet<AllocaInst*, 4>::iterator I = deadPointers.begin(),
for (SmallPtrSet<AllocaInst*, 64>::iterator I = deadPointers.begin(),
E = deadPointers.end(); I != E; ++I) {
// Get size information for the alloca
unsigned pointerSize = ~0UL;
@ -343,7 +348,7 @@ bool DSE::RemoveUndeadPointers(Value* killPointer, unsigned killPointerSize,
// See if this pointer could alias it
AliasAnalysis::AliasResult A = AA.alias(*I, pointerSize,
killPointer, killPointerSize);
killPointer, ~0UL);
// If it must-alias and a store, we can delete it
if (isa<StoreInst>(BBI) && A == AliasAnalysis::MustAlias) {
@ -377,6 +382,10 @@ bool DSE::RemoveUndeadPointers(Value* killPointer, unsigned killPointerSize,
return MadeChange;
}
/// DeleteDeadInstructionChains - takes an instruction and a setvector of
/// dead instructions. If I is dead, it is erased, and its operands are
/// checked for deadness. If they are dead, they are added to the dead
/// setvector.
void DSE::DeleteDeadInstructionChains(Instruction *I,
SetVector<Instruction*> &DeadInsts) {
// Instruction must be dead.