Author: resistor
Date: Tue Aug 14 13:16:29 2007
New Revision: 41080
URL: http://llvm.org/viewvc/llvm-project?rev=41080&view=rev
Log:
Be more aggressive in pruning unnecessary PHI nodes when doing PHI construction.
Modified:
llvm/trunk/lib/Transforms/Scalar/GVN.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=41080&r1=41079&r2=41080&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Tue Aug 14 13:16:29 2007
@@ -749,40 +749,59 @@
if (Phis.count(BB) == 0)
Phis.insert(std::make_pair(BB, PN));
- bool all_same = true;
- Value* first = 0;
-
// Fill in the incoming values for the block.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
Value* val = GetValueForBlock(*PI, orig, Phis);
- if (first == 0)
- first = val;
- else if (all_same && first != val)
- all_same = false;
PN->addIncoming(val, *PI);
}
- if (all_same) {
- MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
-
- MD.removeInstruction(PN);
- PN->replaceAllUsesWith(first);
-
- SmallVector<BasicBlock*, 4> toRemove;
- for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(),
- E = Phis.end(); I != E; ++I)
- if (I->second == PN)
- toRemove.push_back(I->first);
- for (SmallVector<BasicBlock*, 4>::iterator I = toRemove.begin(),
- E= toRemove.end(); I != E; ++I)
- Phis[*I] = first;
-
- PN->eraseFromParent();
-
- Phis[BB] = first;
-
- return first;
+ Value* v = PN->hasConstantValue();
+ if (v) {
+ if (Instruction* inst = dyn_cast<Instruction>(v)) {
+ DominatorTree &DT = getAnalysis<DominatorTree>();
+ if (DT.dominates(inst, PN)) {
+ MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
+
+ MD.removeInstruction(PN);
+ PN->replaceAllUsesWith(inst);
+
+ SmallVector<BasicBlock*, 4> toRemove;
+ for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(),
+ E = Phis.end(); I != E; ++I)
+ if (I->second == PN)
+ toRemove.push_back(I->first);
+ for (SmallVector<BasicBlock*, 4>::iterator I = toRemove.begin(),
+ E= toRemove.end(); I != E; ++I)
+ Phis[*I] = inst;
+
+ PN->eraseFromParent();
+
+ Phis[BB] = inst;
+
+ return inst;
+ }
+ } else {
+ MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
+
+ MD.removeInstruction(PN);
+ PN->replaceAllUsesWith(v);
+
+ SmallVector<BasicBlock*, 4> toRemove;
+ for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(),
+ E = Phis.end(); I != E; ++I)
+ if (I->second == PN)
+ toRemove.push_back(I->first);
+ for (SmallVector<BasicBlock*, 4>::iterator I = toRemove.begin(),
+ E= toRemove.end(); I != E; ++I)
+ Phis[*I] = v;
+
+ PN->eraseFromParent();
+
+ Phis[BB] = v;
+
+ return v;
+ }
}
phiMap[orig->getPointerOperand()].insert(PN);
@@ -915,7 +934,7 @@
return deletedLoad;
}
-/// buildsets_availout - When calculating availability, handle an instruction
+/// processInstruction - When calculating availability, handle an instruction
/// by inserting it into the appropriate sets
bool GVN::processInstruction(Instruction* I,
ValueNumberedSet& currAvail,
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