[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

src/compiler/typer.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/typer.h"
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/common-operator.h"
@@ skipping 2199 matching lines @@
 Type* Typer::Visitor::TypeUint64LessThan(Node* node) { return Type::Boolean(); }
 
 
 Type* Typer::Visitor::TypeUint64LessThanOrEqual(Node* node) {
   return Type::Boolean();
 }
 
 
 Type* Typer::Visitor::TypeUint64Mod(Node* node) { return Type::Internal(); }
 
+Type* Typer::Visitor::TypeBitcastWordToTagged(Node* node) {
+  return Type::TaggedPointer();
+}
 
 Type* Typer::Visitor::TypeChangeFloat32ToFloat64(Node* node) {
   return Type::Intersect(Type::Number(), Type::UntaggedFloat64(), zone());
 }
 
 
 Type* Typer::Visitor::TypeChangeFloat64ToInt32(Node* node) {
   return Type::Intersect(Type::Signed32(), Type::UntaggedIntegral32(), zone());
 }
 
@@ skipping 330 matching lines @@
   }
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8