[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

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 451 matching lines @@
   }
   Node* Float64LessThanOrEqual(Node* a, Node* b) {
     return AddNode(machine()->Float64LessThanOrEqual(), a, b);
   }
   Node* Float64GreaterThan(Node* a, Node* b) { return Float64LessThan(b, a); }
   Node* Float64GreaterThanOrEqual(Node* a, Node* b) {
     return Float64LessThanOrEqual(b, a);
   }
 
   // Conversions.
+  Node* BitcastWordToTagged(Node* a) {
+    return AddNode(machine()->BitcastWordToTagged(), a);
+  }
   Node* ChangeFloat32ToFloat64(Node* a) {
     return AddNode(machine()->ChangeFloat32ToFloat64(), a);
   }
   Node* ChangeInt32ToFloat64(Node* a) {
     return AddNode(machine()->ChangeInt32ToFloat64(), a);
   }
   Node* ChangeUint32ToFloat64(Node* a) {
     return AddNode(machine()->ChangeUint32ToFloat64(), a);
   }
   Node* ChangeFloat64ToInt32(Node* a) {
@@ skipping 270 matching lines @@
   bool deferred_;
   friend class RawMachineAssembler;
   DISALLOW_COPY_AND_ASSIGN(RawMachineLabel);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_RAW_MACHINE_ASSEMBLER_H_