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Another 10% performance improvement by not using replaceAllUsesWith

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8994 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-10-09 23:10:14 +00:00
parent 4c52392ba3
commit 97330cf287
1 changed files with 20 additions and 13 deletions

33
lib/Bytecode/Reader/Reader.cpp

@ -269,7 +269,6 @@ void BytecodeParser::ResolveReferencesToValue(Value *NewV, unsigned Slot) {
BCR_TRACE(3, "Mutating forward refs!\n");
Value *VPH = I->second; // Get the placeholder...
VPH->replaceAllUsesWith(NewV);
// If this is a global variable being resolved, remove the placeholder from
@ -382,25 +381,33 @@ void BytecodeParser::materializeFunction(Function* F) {
throw std::string("Illegal basic block operand reference");
ParsedBasicBlocks.clear();
// Resolve forward references. Replace any uses of a forward reference value
// with the real value.
// replaceAllUsesWith is very inefficient for instructions which have a LARGE
// number of operands. PHI nodes often have forward references, and can also
// often have a very large number of operands.
std::map<Value*, Value*> ForwardRefMapping;
for (std::map<std::pair<unsigned,unsigned>, Value*>::iterator
I = ForwardReferences.begin(), E = ForwardReferences.end();
I != E; ++I)
ForwardRefMapping[I->second] = getValue(I->first.first, I->first.second,
false);
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Argument *A = dyn_cast<Argument>(I->getOperand(i))) {
std::map<Value*, Value*>::iterator It = ForwardRefMapping.find(A);
if (It != ForwardRefMapping.end()) I->setOperand(i, It->second);
}
// Resolve forward references
while (!ForwardReferences.empty()) {
std::map<std::pair<unsigned,unsigned>, Value*>::iterator I =
ForwardReferences.begin();
unsigned type = I->first.first;
unsigned Slot = I->first.second;
Value *PlaceHolder = I->second;
ForwardReferences.erase(I);
Value *NewVal = getValue(type, Slot, false);
if (NewVal == 0)
throw std::string("Unresolvable reference found: <" +
PlaceHolder->getType()->getDescription() + ">:" +
utostr(Slot) + ".");
// Fixup all of the uses of this placeholder def...
PlaceHolder->replaceAllUsesWith(NewVal);
// Now that all the uses are gone, delete the placeholder...
// If we couldn't find a def (error case), then leak a little
// memory, because otherwise we can't remove all uses!