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First round of cleanups from Chris' feedback.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40919 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2007-08-08 04:52:29 +00:00
parent 8df786012d
commit 6ca4cb3755
1 changed files with 60 additions and 53 deletions
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113
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -57,16 +57,23 @@ namespace {
SetVector<Instruction*>& possiblyDead);
void DeleteDeadInstructionChains(Instruction *I,
SetVector<Instruction*> &DeadInsts);
// Find the base pointer that a pointer came from
// Because this is used to find pointers that originate
// from allocas, it is safe to ignore GEP indices, since
// either the store will be in the alloca, and thus dead,
// or beyond the end of the alloca, and thus undefined.
void TranslatePointerBitCasts(Value*& v) {
assert(isa<PointerType>(v->getType()) &&
"Translating a non-pointer type?");
// See through pointer-to-pointer bitcasts
while (isa<BitCastInst>(v) || isa<GetElementPtrInst>(v))
while (true) {
if (BitCastInst* C = dyn_cast<BitCastInst>(v))
v = C->getOperand(0);
else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(v))
v = G->getOperand(0);
else
break;
}
}
// getAnalysisUsage - We require post dominance frontiers (aka Control
@ -100,62 +107,62 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
for (BasicBlock::iterator BBI = BB.begin(), BBE = BB.end();
BBI != BBE; ++BBI) {
// If we find a store or a free...
if (isa<StoreInst>(BBI) || isa<FreeInst>(BBI)) {
Value* pointer = 0;
if (StoreInst* S = dyn_cast<StoreInst>(BBI))
pointer = S->getPointerOperand();
else if (FreeInst* F = dyn_cast<FreeInst>(BBI))
pointer = F->getPointerOperand();
if (!isa<StoreInst>(BBI) && !isa<FreeInst>(BBI))
continue;
assert(pointer && "Not a free or a store?");
Value* pointer = 0;
if (StoreInst* S = dyn_cast<StoreInst>(BBI))
pointer = S->getPointerOperand();
else if (FreeInst* F = dyn_cast<FreeInst>(BBI))
pointer = F->getPointerOperand();
StoreInst*& last = lastStore[pointer];
bool deletedStore = false;
assert(pointer && "Not a free or a store?");
// ... to a pointer that has been stored to before...
if (last) {
StoreInst*& last = lastStore[pointer];
bool deletedStore = false;
// ... to a pointer that has been stored to before...
if (last) {
Instruction* dep = MD.getDependency(BBI);
Instruction* dep = MD.getDependency(BBI);
// ... and no other memory dependencies are between them....
while (dep != MemoryDependenceAnalysis::None &&
dep != MemoryDependenceAnalysis::NonLocal &&
isa<StoreInst>(dep)) {
if (dep == last) {
// Remove it!
MD.removeInstruction(last);
// DCE instructions only used to calculate that store
if (Instruction* D = dyn_cast<Instruction>(last->getOperand(0)))
possiblyDead.insert(D);
if (Instruction* D = dyn_cast<Instruction>(last->getOperand(1)))
possiblyDead.insert(D);
last->eraseFromParent();
NumFastStores++;
deletedStore = true;
MadeChange = true;
break;
} else {
dep = MD.getDependency(BBI, dep);
}
// ... and no other memory dependencies are between them....
while (dep != MemoryDependenceAnalysis::None &&
dep != MemoryDependenceAnalysis::NonLocal &&
isa<StoreInst>(dep)) {
if (dep != last) {
dep = MD.getDependency(BBI, dep);
continue;
}
// Remove it!
MD.removeInstruction(last);
// DCE instructions only used to calculate that store
if (Instruction* D = dyn_cast<Instruction>(last->getOperand(0)))
possiblyDead.insert(D);
if (Instruction* D = dyn_cast<Instruction>(last->getOperand(1)))
possiblyDead.insert(D);
last->eraseFromParent();
NumFastStores++;
deletedStore = true;
MadeChange = true;
break;
}
// Handle frees whose dependencies are non-trivial
if (FreeInst* F = dyn_cast<FreeInst>(BBI))
if (!deletedStore)
MadeChange |= handleFreeWithNonTrivialDependency(F,
MD.getDependency(F),
possiblyDead);
// Update our most-recent-store map
if (StoreInst* S = dyn_cast<StoreInst>(BBI))
last = S;
else
last = 0;
}
// Handle frees whose dependencies are non-trivial.
if (FreeInst* F = dyn_cast<FreeInst>(BBI)) {
if (!deletedStore)
MadeChange |= handleFreeWithNonTrivialDependency(F,
MD.getDependency(F),
possiblyDead);
// No known stores after the free
last = 0;
} else {
// Update our most-recent-store map.
last = cast<StoreInst>(BBI);
}
}