[stubs] Fix some CodeStubAssembler macros and adds a bitcast in the ToObjectStub.

src/compiler/code-assembler.cc

 // Copyright 2015 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/code-assembler.h"
 
 #include <ostream>
 
 #include "src/code-factory.h"
 #include "src/compiler/graph.h"
@@ skipping 89 matching lines @@
 
 Node* CodeAssembler::IntPtrConstant(intptr_t value) {
   return raw_assembler_->IntPtrConstant(value);
 }
 
 Node* CodeAssembler::NumberConstant(double value) {
   return raw_assembler_->NumberConstant(value);
 }
 
 Node* CodeAssembler::SmiConstant(Smi* value) {
-  return IntPtrConstant(bit_cast<intptr_t>(value));
+  return BitcastWordToTaggedSigned(IntPtrConstant(bit_cast<intptr_t>(value)));
 }
 
 Node* CodeAssembler::HeapConstant(Handle<HeapObject> object) {
   return raw_assembler_->HeapConstant(object);
 }
 
 Node* CodeAssembler::BooleanConstant(bool value) {
   return raw_assembler_->BooleanConstant(value);
 }
 
@@ skipping 996 matching lines @@
       }
     }
   }
 
   bound_ = true;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8