Speed up conversion of untagged int32 result if we know it must be a smi.

src/ia32/codegen-ia32.h

 // Copyright 2010 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 355 matching lines @@
   void set_safe_int32_mode_enabled(bool value) {
     safe_int32_mode_enabled_ = value;
   }
   void set_unsafe_bailout(BreakTarget* unsafe_bailout) {
     unsafe_bailout_ = unsafe_bailout;
   }
 
   // Take the Result that is an untagged int32, and convert it to a tagged
   // Smi or HeapNumber.  Remove the untagged_int32 flag from the result.
   void ConvertInt32ResultToNumber(Result* value);
+  void ConvertInt32ResultToSmi(Result* value);
 
   // Track loop nesting level.
   int loop_nesting() const { return loop_nesting_; }
   void IncrementLoopNesting() { loop_nesting_++; }
   void DecrementLoopNesting() { loop_nesting_--; }
 
   // Node visitors.
   void VisitStatements(ZoneList<Statement*>* statements);
 
 #define DEF_VISIT(type) \
@@ skipping 664 matching lines @@
     return ObjectBits::encode(object_.code()) |
            AddressBits::encode(addr_.code()) |
            ScratchBits::encode(scratch_.code());
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_CODEGEN_IA32_H_