[wasm] Int64Lowering of Word64Ctz.

src/compiler/machine-operator.cc

Index: src/compiler/machine-operator.cc
diff --git a/src/compiler/machine-operator.cc b/src/compiler/machine-operator.cc
index fab367c4572aa447839b4a6a80ecc69975b9c23a..be491a4cb0f2b0c67a77985f9c0e80d032b2f997 100644
--- a/src/compiler/machine-operator.cc
+++ b/src/compiler/machine-operator.cc
@@ -478,6 +478,13 @@ const Operator* MachineOperatorBuilder::CheckedStore(
 const Operator* MachineOperatorBuilder::Word64PopcntPlaceholder() {
   return &cache_.kWord64Popcnt;
 }
+
+// On 32 bit platforms we need to get a reference to optional operators of
+// 64-bit instructions for later Int64Lowering, even though 32 bit platforms
+// don't support the original 64-bit instruction.
+const Operator* MachineOperatorBuilder::Word64CtzPlaceholder() {
+  return &cache_.kWord64Ctz;
+}
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8