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

src/compiler/verifier.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/verifier.h"
 
 #include <algorithm>
 #include <deque>
 #include <queue>
 #include <sstream>
@@ skipping 806 matching lines @@
     case IrOpcode::kWord32Clz:
     case IrOpcode::kWord32Ctz:
     case IrOpcode::kWord32Popcnt:
     case IrOpcode::kWord64And:
     case IrOpcode::kWord64Or:
     case IrOpcode::kWord64Xor:
     case IrOpcode::kWord64Shl:
     case IrOpcode::kWord64Shr:
     case IrOpcode::kWord64Sar:
     case IrOpcode::kWord64Ror:
+    case IrOpcode::kWord64Clz:
     case IrOpcode::kWord64Equal:
     case IrOpcode::kInt32Add:
     case IrOpcode::kInt32AddWithOverflow:
     case IrOpcode::kInt32Sub:
     case IrOpcode::kInt32SubWithOverflow:
     case IrOpcode::kInt32Mul:
     case IrOpcode::kInt32MulHigh:
     case IrOpcode::kInt32Div:
     case IrOpcode::kInt32Mod:
     case IrOpcode::kInt32LessThan:
@@ skipping 386 matching lines @@
          replacement->op()->EffectOutputCount() > 0);
   DCHECK(!NodeProperties::IsFrameStateEdge(edge) ||
          replacement->opcode() == IrOpcode::kFrameState);
 }
 
 #endif  // DEBUG
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8