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Handle eliminating stores that occur right before a free. 

llvm-svn: 39753
This commit is contained in:
Owen Anderson 2007-07-11 20:38:34 +00:00
parent 3d70855dd2
commit e720144837
1 changed files with 15 additions and 4 deletions
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19
llvm/lib/Transforms/Scalar/FastDSE.cpp
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@ -74,14 +74,22 @@ bool FDSE::runOnBasicBlock(BasicBlock &BB) {
// Do a top-down walk on the BB
for (BasicBlock::iterator BBI = BB.begin(), BBE = BB.end(); BBI != BBE; ++BBI) {
// If we find a store...
if (StoreInst* S = dyn_cast<StoreInst>(BBI)) {
StoreInst*& last = lastStore[S->getPointerOperand()];
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();
assert(pointer && "Not a free or a store?");
StoreInst*& last = lastStore[pointer];
// ... to a pointer that has been stored to before...
if (last) {
// ... and no other memory dependencies are between them....
if (MD.getDependency(S) == last) {
if (MD.getDependency(BBI) == last) {
// Remove it!
MD.removeInstruction(last);
@ -96,7 +104,10 @@ bool FDSE::runOnBasicBlock(BasicBlock &BB) {
}
// Update our most-recent-store map
last = S;
if (StoreInst* S = dyn_cast<StoreInst>(BBI))
last = S;
else
last = 0;
}
}