Fix bogus AbortIfNotZeroExtended on x64 for bounds checks

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 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 3589 matching lines @@
         break;
     }
   }
 }
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
   if (instr->length()->IsRegister()) {
     Register reg = ToRegister(instr->length());
     if (FLAG_debug_code &&
-        !instr->hydrogen()->index()->representation().IsTagged()) {
+        !instr->hydrogen()->length()->representation().IsTagged()) {
       __ AbortIfNotZeroExtended(reg);
     }
     if (instr->index()->IsConstantOperand()) {
       __ cmpq(reg,
               Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
     } else {
       Register reg2 = ToRegister(instr->index());
       if (FLAG_debug_code &&
           !instr->hydrogen()->index()->representation().IsTagged()) {
         __ AbortIfNotZeroExtended(reg2);
@@ skipping 1450 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64