MIPS64: fix wrong register use in LoadIndexedStringStub.

src/mips64/code-stubs-mips64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 1329 matching lines @@
   __ Jump(ra);
 }
 
 
 void LoadIndexedStringStub::Generate(MacroAssembler* masm) {
   // Return address is in ra.
   Label miss;
 
   Register receiver = LoadDescriptor::ReceiverRegister();
   Register index = LoadDescriptor::NameRegister();
-  Register scratch = a4;
+  Register scratch = a5;
   Register result = v0;
   DCHECK(!scratch.is(receiver) && !scratch.is(index));
   DCHECK(!FLAG_vector_ics ||
          (!scratch.is(VectorLoadICDescriptor::VectorRegister()) &&
           result.is(VectorLoadICDescriptor::SlotRegister())));
 
   // StringCharAtGenerator doesn't use the result register until it's passed
   // the different miss possibilities. If it did, we would have a conflict
   // when FLAG_vector_ics is true.
   StringCharAtGenerator char_at_generator(receiver, index, scratch, result,
@@ skipping 3821 matching lines @@
                            kStackUnwindSpace, NULL,
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS64