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Be more aggressive in pruning unnecessary PHI nodes when doing PHI construction. 

llvm-svn: 41080
This commit is contained in:
Owen Anderson 2007-08-14 18:16:29 +00:00
parent c48affb81f
commit 398602a6eb
1 changed files with 47 additions and 28 deletions
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75
llvm/lib/Transforms/Scalar/GVN.cpp
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@ -749,40 +749,59 @@ Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig,
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 @@ bool GVN::processLoad(LoadInst* L,
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,