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Make sure to reprocess instructions used by deleted instructions to avoid 

missing opportunities for combination.

llvm-svn: 13309
This commit is contained in:
Chris Lattner 2004-05-01 23:27:23 +00:00
parent b643a9e675
commit 63d75af920
1 changed files with 12 additions and 5 deletions
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17
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2997,6 +2997,8 @@ bool InstCombiner::runOnFunction(Function &F) {
BasicBlock *InstParent = I->getParent();
InstParent->getInstList().insert(I, Result);
// Make sure that we reprocess all operands now that we reduced their
// use counts.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(OpI);
@ -3009,14 +3011,19 @@ bool InstCombiner::runOnFunction(Function &F) {
} else {
DEBUG(std::cerr << "IC: MOD = " << *I);
BasicBlock::iterator II = I;
// If the instruction was modified, it's possible that it is now dead.
// if so, remove it.
if (dceInstruction(II)) {
// Instructions may end up in the worklist more than once. Erase them
// all.
if (isInstructionTriviallyDead(I)) {
// Make sure we process all operands now that we are reducing their
// use counts.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(OpI);
// Instructions may end up in the worklist more than once. Erase all
// occurrances of this instruction.
removeFromWorkList(I);
I->getParent()->getInstList().erase(I);
Result = 0;
}
}