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

src/compiler/arm64/instruction-selector-arm64.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/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 903 matching lines @@
 void InstructionSelector::VisitWord32Ror(Node* node) {
   VisitRRO(this, kArm64Ror32, node, kShift32Imm);
 }
 
 
 void InstructionSelector::VisitWord64Ror(Node* node) {
   VisitRRO(this, kArm64Ror, node, kShift64Imm);
 }
 
 
+void InstructionSelector::VisitWord64Clz(Node* node) {
+  Arm64OperandGenerator g(this);
+  Emit(kArm64Clz, g.DefineAsRegister(node), g.UseRegister(node->InputAt(0)));
+}
+
+
 void InstructionSelector::VisitWord32Clz(Node* node) {
   Arm64OperandGenerator g(this);
   Emit(kArm64Clz32, g.DefineAsRegister(node), g.UseRegister(node->InputAt(0)));
 }
 
 
 void InstructionSelector::VisitWord32Ctz(Node* node) { UNREACHABLE(); }
 
 
 void InstructionSelector::VisitWord32Popcnt(Node* node) { UNREACHABLE(); }
@@ skipping 1045 matching lines @@
          MachineOperatorBuilder::kFloat64RoundTruncate |
          MachineOperatorBuilder::kFloat64RoundTiesAway |
          MachineOperatorBuilder::kWord32ShiftIsSafe |
          MachineOperatorBuilder::kInt32DivIsSafe |
          MachineOperatorBuilder::kUint32DivIsSafe;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8