Fix lowering of cttz to work with signed values
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21874 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/IntrinsicLowering.cpp b/lib/CodeGen/IntrinsicLowering.cpp
index 1817ade..634f959 100644
--- a/lib/CodeGen/IntrinsicLowering.cpp
+++ b/lib/CodeGen/IntrinsicLowering.cpp
@@ -251,13 +251,12 @@
break;
}
case Intrinsic::cttz: {
+ // cttz(x) -> ctpop(~X & (X-1))
Value *Src = CI->getOperand(1);
Value *NotSrc = BinaryOperator::createNot(Src, Src->getName()+".not", CI);
- Src = BinaryOperator::createAnd(NotSrc,
- BinaryOperator::createSub(Src,
- ConstantUInt::get(CI->getOperand(0)->getType(), 1), "", CI));
-
- Src = LowerCTPOP(Src, CI);
+ Value *SrcM1 = ConstantInt::get(Src->getType(), 1);
+ SrcM1 = BinaryOperator::createSub(Src, SrcM1, "", CI);
+ Src = LowerCTPOP(BinaryOperator::createAnd(NotSrc, SrcM1, "", CI), CI);
CI->replaceAllUsesWith(Src);
break;
}