[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

src/compiler/opcodes.h

 // Copyright 2013 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_OPCODES_H_
 #define V8_COMPILER_OPCODES_H_
 
 #include <iosfwd>
 
 // Opcodes for control operators.
@@ skipping 267 matching lines @@
   V(Uint32MulHigh)              \
   V(Int64Add)                   \
   V(Int64AddWithOverflow)       \
   V(Int64Sub)                   \
   V(Int64SubWithOverflow)       \
   V(Int64Mul)                   \
   V(Int64Div)                   \
   V(Int64Mod)                   \
   V(Uint64Div)                  \
   V(Uint64Mod)                  \
+  V(BitcastWordToTagged)        \
   V(ChangeFloat32ToFloat64)     \
   V(ChangeFloat64ToInt32)       \
   V(ChangeFloat64ToUint32)      \
   V(TruncateFloat64ToUint32)    \
   V(TruncateFloat32ToInt32)     \
   V(TruncateFloat32ToUint32)    \
   V(TryTruncateFloat32ToInt64)  \
   V(TryTruncateFloat64ToInt64)  \
   V(TryTruncateFloat32ToUint64) \
   V(TryTruncateFloat64ToUint64) \
@@ skipping 134 matching lines @@
   }
 };
 
 std::ostream& operator<<(std::ostream&, IrOpcode::Value);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_