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DCE intrinsic instructions without side effects.

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llvm-svn: 21719
This commit is contained in:
Chris Lattner 2005-05-06 05:27:34 +00:00
parent 4f7bba1106
commit b953e27f85
1 changed files with 20 additions and 1 deletions
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21
lib/Transforms/Utils/Local.cpp
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@ -373,7 +373,26 @@ Constant *llvm::ConstantFoldCall(Function *F,
//
bool llvm::isInstructionTriviallyDead(Instruction *I) {
return I->use_empty() && !I->mayWriteToMemory() && !isa<TerminatorInst>(I);
if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
if (!I->mayWriteToMemory()) return true;
if (CallInst *CI = dyn_cast<CallInst>(I))
if (Function *F = CI->getCalledFunction())
switch (F->getIntrinsicID()) {
default: break;
case Intrinsic::vastart:
case Intrinsic::vacopy:
case Intrinsic::returnaddress:
case Intrinsic::frameaddress:
case Intrinsic::isunordered:
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
case Intrinsic::sqrt:
return true; // These intrinsics have no side effects.
}
return false;
}
// dceInstruction - Inspect the instruction at *BBI and figure out if it's