Faster filling newly allocated arrays with the holes from the Array construction stub.

test/cctest/test-disasm-ia32.cc

 // Copyright 2007-2008 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 216 matching lines @@
   __ sub(Operand(edx, ecx, times_4, 10000), Immediate(12));
   __ subb(Operand(edx, ecx, times_4, 10000), 100);
   __ subb(Operand(eax), 100);
   __ subb(eax, Operand(edx, ecx, times_4, 10000));
 
   __ xor_(ebx, 12345);
 
   __ imul(edx, ecx, 12);
   __ imul(edx, ecx, 1000);
 
+  __ cld();
   __ rep_movs();
+  __ rep_stos();
 
   __ sub(edx, Operand(ebx, ecx, times_4, 10000));
   __ sub(edx, Operand(ebx));
 
   __ test(edx, Immediate(12345));
   __ test(edx, Operand(ebx, ecx, times_8, 10000));
   __ nop();
 
   __ xor_(edx, 12345);
   __ xor_(edx, Operand(ebx, ecx, times_8, 10000));
@@ skipping 163 matching lines @@
   CHECK(code->IsCode());
 #ifdef DEBUG
   Code::cast(code)->Print();
   byte* begin = Code::cast(code)->instruction_start();
   byte* end = begin + Code::cast(code)->instruction_size();
   disasm::Disassembler::Disassemble(stdout, begin, end);
 #endif
 }
 
 #undef __