Initialize pre-allocated fields of JSObject with undefined.

src/ia32/macro-assembler-ia32.h

 // Copyright 2011 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 439 matching lines @@
                                  Label* gc_required);
 
   // Copy memory, byte-by-byte, from source to destination.  Not optimized for
   // long or aligned copies.
   // The contents of index and scratch are destroyed.
   void CopyBytes(Register source,
                  Register destination,
                  Register length,
                  Register scratch);
 
+  // Initialize fields with filler values.  Fields starting at |start_offset|
+  // not including end_offset are overwritten with the value in |filler|.  At
+  // the end the loop, |start_offset| takes the value of |end_offset|.
+  void InitializeFieldsWithFiller(Register start_offset,
+                                  Register end_offset,
+                                  Register filler);
+
   // ---------------------------------------------------------------------------
   // Support functions.
 
   // Check if result is zero and op is negative.
   void NegativeZeroTest(Register result, Register op, Label* then_label);
 
   // Check if result is zero and any of op1 and op2 are negative.
   // Register scratch is destroyed, and it must be different from op2.
   void NegativeZeroTest(Register result, Register op1, Register op2,
                         Register scratch, Label* then_label);
@@ skipping 336 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_