CTZ instruction implemented as optional operator.

src/compiler/x87/instruction-selector-x87.cc

Index: src/compiler/x87/instruction-selector-x87.cc
diff --git a/src/compiler/x87/instruction-selector-x87.cc b/src/compiler/x87/instruction-selector-x87.cc
index ac868fb932b71adbcb60bf514db72c4f3b39bc18..64b6eed32a81ec382f2afc8a5306b726af730641 100644
--- a/src/compiler/x87/instruction-selector-x87.cc
+++ b/src/compiler/x87/instruction-selector-x87.cc
@@ -514,6 +514,9 @@ void InstructionSelector::VisitWord32Clz(Node* node) {
 }
 
 
+void InstructionSelector::VisitWord32Ctz(Node* node) { UNREACHABLE(); }
+
+
 void InstructionSelector::VisitInt32Add(Node* node) {
   X87OperandGenerator g(this);