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

src/compiler/raw-machine-assembler.h

 // 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.
 
 #ifndef V8_COMPILER_RAW_MACHINE_ASSEMBLER_H_
 #define V8_COMPILER_RAW_MACHINE_ASSEMBLER_H_
 
 #include "src/assembler.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
@@ skipping 215 matching lines @@
   }
   Node* Word64Shr(Node* a, Node* b) {
     return AddNode(machine()->Word64Shr(), a, b);
   }
   Node* Word64Sar(Node* a, Node* b) {
     return AddNode(machine()->Word64Sar(), a, b);
   }
   Node* Word64Ror(Node* a, Node* b) {
     return AddNode(machine()->Word64Ror(), a, b);
   }
+  Node* Word64Clz(Node* a) { return AddNode(machine()->Word64Clz(), a); }
   Node* Word64Equal(Node* a, Node* b) {
     return AddNode(machine()->Word64Equal(), a, b);
   }
   Node* Word64NotEqual(Node* a, Node* b) {
     return Word64BinaryNot(Word64Equal(a, b));
   }
   Node* Word64Not(Node* a) { return Word64Xor(a, Int64Constant(-1)); }
   Node* Word64BinaryNot(Node* a) { return Word64Equal(a, Int64Constant(0)); }
 
   Node* Int32Add(Node* a, Node* b) {
@@ skipping 360 matching lines @@
   BasicBlock* current_block_;
 
   DISALLOW_COPY_AND_ASSIGN(RawMachineAssembler);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_RAW_MACHINE_ASSEMBLER_H_