1 files changed, 6 insertions, 2 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 760c4e5..d10fa46 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4948,14 +4948,18 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     return 0;
   case Intrinsic::cttz: {
     SDValue Arg = getValue(I.getArgOperand(0));
+    ConstantInt *CI = cast<ConstantInt>(I.getArgOperand(1));
     EVT Ty = Arg.getValueType();
-    setValue(&I, DAG.getNode(ISD::CTTZ, dl, Ty, Arg));
+    setValue(&I, DAG.getNode(CI->isZero() ? ISD::CTTZ : ISD::CTTZ_ZERO_UNDEF,
+                             dl, Ty, Arg));
     return 0;
   }
   case Intrinsic::ctlz: {
     SDValue Arg = getValue(I.getArgOperand(0));
+    ConstantInt *CI = cast<ConstantInt>(I.getArgOperand(1));
     EVT Ty = Arg.getValueType();
-    setValue(&I, DAG.getNode(ISD::CTLZ, dl, Ty, Arg));
+    setValue(&I, DAG.getNode(CI->isZero() ? ISD::CTLZ : ISD::CTLZ_ZERO_UNDEF,
+                             dl, Ty, Arg));
     return 0;
   }
   case Intrinsic::ctpop: {