MIPS: Fix a bug in MacroAssembler::CheckFastElements.

src/mips/macro-assembler-mips.cc

 // Copyright 2011 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 2639 matching lines @@
   Subu(length, length, Operand(1));
   Branch(&byte_loop_1, ne, length, Operand(zero_reg));
   bind(&done);
 }
 
 
 void MacroAssembler::CheckFastElements(Register map,
                                        Register scratch,
                                        Label* fail) {
   STATIC_ASSERT(JSObject::FAST_ELEMENTS == 0);
-  lbu(scratch, FieldMemOperand(map, Map::kBitField2Offset));
-  And(scratch, scratch, Operand(Map::kMaximumBitField2FastElementValue));
-  Branch(fail, hi, scratch, Operand(zero_reg));
+  lbu(scratch, FieldMemOperand(map, Map::kInstanceTypeOffset));
+  Branch(fail, hi, scratch, Operand(Map::kMaximumBitField2FastElementValue));
 }
 
 
 void MacroAssembler::CheckMap(Register obj,
                               Register scratch,
                               Handle<Map> map,
                               Label* fail,
                               SmiCheckType smi_check_type) {
   if (smi_check_type == DO_SMI_CHECK) {
     JumpIfSmi(obj, fail);
@@ skipping 1434 matching lines @@
        opcode == BGTZL);
   opcode = (cond == eq) ? BEQ : BNE;
   instr = (instr & ~kOpcodeMask) | opcode;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS