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

src/compiler/mips64/instruction-selector-mips64.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/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 314 matching lines @@
 
 
 void InstructionSelector::VisitWord32Popcnt(Node* node) { UNREACHABLE(); }
 
 
 void InstructionSelector::VisitWord64Ror(Node* node) {
   VisitRRO(this, kMips64Dror, node);
 }
 
 
+void InstructionSelector::VisitWord64Clz(Node* node) {
+  VisitRR(this, kMips64Dclz, node);
+}
+
+
 void InstructionSelector::VisitInt32Add(Node* node) {
   Mips64OperandGenerator g(this);
   // TODO(plind): Consider multiply & add optimization from arm port.
   VisitBinop(this, node, kMips64Add);
 }
 
 
 void InstructionSelector::VisitInt64Add(Node* node) {
   Mips64OperandGenerator g(this);
   // TODO(plind): Consider multiply & add optimization from arm port.
@@ skipping 1003 matching lines @@
          MachineOperatorBuilder::kFloat64Max |
          MachineOperatorBuilder::kFloat32Min |
          MachineOperatorBuilder::kFloat32Max |
          MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat64RoundTruncate;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8