Promoting elements transitions to their own field.

src/mips/macro-assembler-mips.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 3463 matching lines @@
                                          CompareMapMode mode) {
   lw(scratch, FieldMemOperand(obj, HeapObject::kMapOffset));
   Operand right = Operand(map);
   if (mode == ALLOW_ELEMENT_TRANSITION_MAPS) {
     ElementsKind kind = map->elements_kind();
     if (IsFastElementsKind(kind)) {
       bool packed = IsFastPackedElementsKind(kind);
       Map* current_map = *map;
       while (CanTransitionToMoreGeneralFastElementsKind(kind, packed)) {
         kind = GetNextMoreGeneralFastElementsKind(kind, packed);
-        current_map = current_map->LookupElementsTransitionMap(kind, NULL);
+        current_map = current_map->LookupElementsTransitionMap(kind);
         if (!current_map) break;
         Branch(early_success, eq, scratch, right);
         right = Operand(Handle<Map>(current_map));
       }
     }
   }
 
   Branch(branch_to, cond, scratch, right);
 }
 
@@ skipping 1940 matching lines @@
        opcode == BGTZL);
   opcode = (cond == eq) ? BEQ : BNE;
   instr = (instr & ~kOpcodeMask) | opcode;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS