Implemented the Word64Clz TurboFan operator for x64, arm64, and mips64.

src/compiler/machine-operator.h

 // Copyright 2013 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.
 
 #ifndef V8_COMPILER_MACHINE_OPERATOR_H_
 #define V8_COMPILER_MACHINE_OPERATOR_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/machine-type.h"
 
@@ skipping 130 matching lines @@
   const OptionalOperator Word32Popcnt();
   bool Word32ShiftIsSafe() const { return flags_ & kWord32ShiftIsSafe; }
 
   const Operator* Word64And();
   const Operator* Word64Or();
   const Operator* Word64Xor();
   const Operator* Word64Shl();
   const Operator* Word64Shr();
   const Operator* Word64Sar();
   const Operator* Word64Ror();
+  const Operator* Word64Clz();
   const Operator* Word64Equal();
 
   const Operator* Int32Add();
   const Operator* Int32AddWithOverflow();
   const Operator* Int32Sub();
   const Operator* Int32SubWithOverflow();
   const Operator* Int32Mul();
   const Operator* Int32MulHigh();
   const Operator* Int32Div();
   const Operator* Int32Mod();
@@ skipping 156 matching lines @@
 };
 
 
 DEFINE_OPERATORS_FOR_FLAGS(MachineOperatorBuilder::Flags)
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_MACHINE_OPERATOR_H_