Author: resistor
Date: Tue Aug 7 23:52:29 2007
New Revision: 40919
URL: http://llvm.org/viewvc/llvm-project?rev=40919&view=rev
Log:
First round of cleanups from Chris' feedback.
Modified:
llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp?rev=40919&r1=40918&r2=40919&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp Tue Aug 7
23:52:29 2007
@@ -57,16 +57,23 @@
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 @@
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) {
+ dep = MD.getDependency(BBI, dep);
+ continue;
+ }
- // ... 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);
+ // 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);
+ // 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);
- }
- }
+ 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);
}
}
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