Revert "Changing string length field type from int to SMI."

src/x64/stub-cache-x64.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 309 matching lines @@
                                             Register scratch1,
                                             Register scratch2,
                                             Label* miss) {
   Label check_wrapper;
 
   // Check if the object is a string leaving the instance type in the
   // scratch register.
   GenerateStringCheck(masm, receiver, scratch1, miss, &check_wrapper);
 
   // Load length directly from the string.
-  __ movq(rax, FieldOperand(receiver, String::kLengthOffset));
+  __ movl(rax, FieldOperand(receiver, String::kLengthOffset));
+  __ Integer32ToSmi(rax, rax);
   __ ret(0);
 
   // Check if the object is a JSValue wrapper.
   __ bind(&check_wrapper);
   __ cmpl(scratch1, Immediate(JS_VALUE_TYPE));
   __ j(not_equal, miss);
 
   // Check if the wrapped value is a string and load the length
   // directly if it is.
   __ movq(scratch2, FieldOperand(receiver, JSValue::kValueOffset));
   GenerateStringCheck(masm, scratch2, scratch1, miss, miss);
-  __ movq(rax, FieldOperand(scratch2, String::kLengthOffset));
+  __ movl(rax, FieldOperand(scratch2, String::kLengthOffset));
+  __ Integer32ToSmi(rax, rax);
   __ ret(0);
 }
 
 
 static void CompileCallLoadPropertyWithInterceptor(MacroAssembler* masm,
                                                    Register receiver,
                                                    Register holder,
                                                    Register name,
                                                    JSObject* holder_obj) {
   PushInterceptorArguments(masm, receiver, holder, name, holder_obj);
@@ skipping 1667 matching lines @@
   __ Jump(generic_construct_stub, RelocInfo::CODE_TARGET);
 
   // Return the generated code.
   return GetCode();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal