MIPS: Fix unpredictable random failures after direct api function call.

src/mips/code-stubs-mips.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_MIPS
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 4033 matching lines @@
   }
   __ Jump(t9);
 }
 
 
 void DirectCEntryStub::GenerateCall(MacroAssembler* masm,
                                     Register target) {
   intptr_t loc =
       reinterpret_cast<intptr_t>(GetCode().location());
   __ Move(t9, target);
-  __ li(ra, Operand(loc, RelocInfo::CODE_TARGET), CONSTANT_SIZE);
-  __ Call(ra);
+  __ li(at, Operand(loc, RelocInfo::CODE_TARGET), CONSTANT_SIZE);
+  __ Call(at);
 }
 
 
 void NameDictionaryLookupStub::GenerateNegativeLookup(MacroAssembler* masm,
                                                       Label* miss,
                                                       Label* done,
                                                       Register receiver,
                                                       Register properties,
                                                       Handle<Name> name,
                                                       Register scratch0) {
@@ skipping 1508 matching lines @@
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS