CTZ instruction implemented as optional operator.

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index 91db46b8287592c5ac8468fdf745b004d48248d5..cbad0c8db2d1f1b39a4195edadfcc9e4b8b8f12c 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -611,6 +611,8 @@ void InstructionSelector::VisitNode(Node* node) {
       return VisitWord32Equal(node);
     case IrOpcode::kWord32Clz:
       return MarkAsWord32(node), VisitWord32Clz(node);
+    case IrOpcode::kWord32Ctz:
+      return MarkAsWord32(node), VisitWord32Ctz(node);
     case IrOpcode::kWord64And:
       return MarkAsWord64(node), VisitWord64And(node);
     case IrOpcode::kWord64Or: