Initialize pre-allocated fields of JSObject with undefined.

src/ia32/macro-assembler-ia32.cc

 // 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 1276 matching lines @@
   mov_b(Operand(destination, 0), scratch);
   inc(source);
   inc(destination);
   dec(length);
   j(not_zero, &short_loop);
 
   bind(&done);
 }
 
 
+void MacroAssembler::InitializeFieldsWithFiller(Register start_offset,
+                                                Register end_offset,
+                                                Register filler) {
+  Label loop, entry;
+  jmp(&entry);
+  bind(&loop);
+  mov(Operand(start_offset, 0), filler);
+  add(Operand(start_offset), Immediate(kPointerSize));
+  bind(&entry);
+  cmp(start_offset, Operand(end_offset));
+  j(less, &loop);
+}
+
+
 void MacroAssembler::NegativeZeroTest(Register result,
                                       Register op,
                                       Label* then_label) {
   Label ok;
   test(result, Operand(result));
   j(not_zero, &ok);
   test(op, Operand(op));
   j(sign, then_label);
   bind(&ok);
 }
@@ skipping 1004 matching lines @@
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32