[turbofan]: Elide extra move when accessing stack or frame register

src/mips/frames-mips.cc

 // Copyright 2011 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/assembler.h"
 #include "src/frames.h"
 #include "src/mips/assembler-mips-inl.h"
 #include "src/mips/assembler-mips.h"
 
 namespace v8 {
 namespace internal {
 
 
-Register JavaScriptFrame::fp_register() { return v8::internal::fp; }
+Register StandardFrame::sp_register() { return v8::internal::sp; }
+Register StandardFrame::fp_register() { return v8::internal::fp; }
 Register JavaScriptFrame::context_register() { return cp; }
 Register JavaScriptFrame::constant_pool_pointer_register() {
   UNREACHABLE();
   return no_reg;
 }
 
 
 Register StubFailureTrampolineFrame::fp_register() { return v8::internal::fp; }
 Register StubFailureTrampolineFrame::context_register() { return cp; }
 Register StubFailureTrampolineFrame::constant_pool_pointer_register() {
   UNREACHABLE();
   return no_reg;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS