Fix cast that fails to build on Windows.

src/ia32/full-codegen-ia32.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 2678 matching lines @@
   __ pop(left);
 
   Label done, fail, ok;
   __ cmp(left, Operand(right));
   __ j(equal, &ok);
   // Fail if either is a non-HeapObject.
   __ mov(tmp, left);
   __ and_(Operand(tmp), right);
   __ test(Operand(tmp), Immediate(kSmiTagMask));
   __ j(zero, &fail);
-  __ mov(tmp, FieldOperand(left, HeapObject::kMapOffset));
-  __ cmpb(FieldOperand(tmp, Map::kInstanceTypeOffset),
-          static_cast<int8_t>(JS_REGEXP_TYPE));
+  __ CmpObjectType(left, JS_REGEXP_TYPE, tmp);
   __ j(not_equal, &fail);
   __ cmp(tmp, FieldOperand(right, HeapObject::kMapOffset));
   __ j(not_equal, &fail);
   __ mov(tmp, FieldOperand(left, JSRegExp::kDataOffset));
   __ cmp(tmp, FieldOperand(right, JSRegExp::kDataOffset));
   __ j(equal, &ok);
   __ bind(&fail);
   __ mov(eax, Immediate(Factory::false_value()));
   __ jmp(&done);
   __ bind(&ok);
@@ skipping 626 matching lines @@
   // And return.
   __ ret(0);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32