Fix improper usage of SmiUntag operation in CodeStubAssembler.

src/code-stub-assembler.cc

 // Copyright 2016 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/code-stub-assembler.h"
 #include "src/code-factory.h"
 
 namespace v8 {
 namespace internal {
 
@@ skipping 241 matching lines @@
 
 Node* CodeStubAssembler::SmiToWord32(Node* value) {
   Node* result = WordSar(value, SmiShiftBitsConstant());
   if (Is64()) {
     result = TruncateInt64ToInt32(result);
   }
   return result;
 }
 
 Node* CodeStubAssembler::SmiToFloat64(Node* value) {
-  return ChangeInt32ToFloat64(SmiUntag(value));
+  return ChangeInt32ToFloat64(SmiToWord32(value));
 }
 
 Node* CodeStubAssembler::SmiAdd(Node* a, Node* b) { return IntPtrAdd(a, b); }
 
 Node* CodeStubAssembler::SmiAddWithOverflow(Node* a, Node* b) {
   return IntPtrAddWithOverflow(a, b);
 }
 
 Node* CodeStubAssembler::SmiSub(Node* a, Node* b) { return IntPtrSub(a, b); }
 
@@ skipping 1138 matching lines @@
 
     Bind(&if_iskeyinrange);
     Node* element = LoadFixedArrayElementInt32Index(elements, index);
     Node* the_hole = LoadRoot(Heap::kTheHoleValueRootIndex);
     Branch(WordEqual(element, the_hole), if_not_found, if_found);
   }
 }
 
 }  // namespace internal
 }  // namespace v8