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

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 81 matching lines @@
   V(Word32Ror, Operator::kNoProperties, 2, 0, 1)                              \
   V(Word32Equal, Operator::kCommutative, 2, 0, 1)                             \
   V(Word32Clz, Operator::kNoProperties, 1, 0, 1)                              \
   V(Word64And, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)      \
   V(Word64Or, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)       \
   V(Word64Xor, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)      \
   V(Word64Shl, Operator::kNoProperties, 2, 0, 1)                              \
   V(Word64Shr, Operator::kNoProperties, 2, 0, 1)                              \
   V(Word64Sar, Operator::kNoProperties, 2, 0, 1)                              \
   V(Word64Ror, Operator::kNoProperties, 2, 0, 1)                              \
+  V(Word64Clz, Operator::kNoProperties, 1, 0, 1)                              \
   V(Word64Equal, Operator::kCommutative, 2, 0, 1)                             \
   V(Int32Add, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)       \
   V(Int32AddWithOverflow, Operator::kAssociative | Operator::kCommutative, 2, \
     0, 2)                                                                     \
   V(Int32Sub, Operator::kNoProperties, 2, 0, 1)                               \
   V(Int32SubWithOverflow, Operator::kNoProperties, 2, 0, 2)                   \
   V(Int32Mul, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)       \
   V(Int32MulHigh, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)   \
   V(Int32Div, Operator::kNoProperties, 2, 1, 1)                               \
   V(Int32Mod, Operator::kNoProperties, 2, 1, 1)                               \
@@ skipping 264 matching lines @@
     default:
       break;
   }
   UNREACHABLE();
   return nullptr;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8