DCE intrinsic instructions without side effects.
llvm-svn: 21719
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 4d14153..0ed6696 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -373,7 +373,26 @@
//
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