The value register in storefield(smi) is not used as a temp

src/mips/lithium-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/hydrogen-osr.h"
 #include "src/lithium-inl.h"
@@ skipping 2293 matching lines @@
     obj = is_in_object
         ? UseRegister(instr->object())
         : UseTempRegister(instr->object());
   } else {
     obj = needs_write_barrier_for_map
         ? UseRegister(instr->object())
         : UseRegisterAtStart(instr->object());
   }
 
   LOperand* val;
-  if (needs_write_barrier || instr->field_representation().IsSmi()) {
+  if (needs_write_barrier) {
     val = UseTempRegister(instr->value());
   } else if (instr->field_representation().IsDouble()) {
     val = UseRegisterAtStart(instr->value());
   } else {
     val = UseRegister(instr->value());
   }
 
   // We need a temporary register for write barrier of the map field.
   LOperand* temp = needs_write_barrier_for_map ? TempRegister() : NULL;
 
@@ skipping 266 matching lines @@
   LOperand* context = UseFixed(instr->context(), cp);
   LOperand* function = UseRegisterAtStart(instr->function());
   LAllocateBlockContext* result =
       new(zone()) LAllocateBlockContext(context, function);
   return MarkAsCall(DefineFixed(result, cp), instr);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS