[wasm] Int64Lowering of Word64Clz.

src/compiler/machine-operator.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/machine-operator.h"
 
 #include "src/base/lazy-instance.h"
 #include "src/compiler/opcodes.h"
 #include "src/compiler/operator.h"
 
@@ skipping 453 matching lines @@
     MACHINE_REPRESENTATION_LIST(STORE)
 #undef STORE
     case MachineRepresentation::kBit:
     case MachineRepresentation::kNone:
       break;
   }
   UNREACHABLE();
   return nullptr;
 }
 
-// On 32 bit platforms we need to get a reference to a Word64Popcnt operator for
-// later lowering, even though 32 bit platforms don't support Word64Popcnt.
+// 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::Word64PopcntPlaceholder() {
   return &cache_.kWord64Popcnt;
 }
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8