MIPS: port Fix a typo in KeyedStoreIC, restore Kraken performance.

src/mips/stub-cache-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 4183 matching lines @@
   Register receiver_reg = a2;
   Register scratch = a3;
   Register elements_reg = t0;
   Register scratch2 = t1;
   Register scratch3 = t2;
 
   // This stub is meant to be tail-jumped to, the receiver must already
   // have been verified by the caller to not be a smi.
 
   // Check that the key is a smi.
-  __ JumpIfNotSmi(a0, &miss_force_generic);
+  __ JumpIfNotSmi(key_reg, &miss_force_generic);
 
   // Get the elements array and make sure it is a fast element array, not 'cow'.
   __ lw(elements_reg,
         FieldMemOperand(receiver_reg, JSObject::kElementsOffset));
   __ CheckMap(elements_reg,
               scratch,
               Heap::kFixedArrayMapRootIndex,
               &miss_force_generic,
               DONT_DO_SMI_CHECK);
 
@@ skipping 23 matching lines @@
       masm->isolate()->builtins()->KeyedStoreIC_MissForceGeneric();
   __ Jump(ic, RelocInfo::CODE_TARGET);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS