Use direct loop when filling small arrays.

Use direct loop when filling small arrays.

r3995 (http://code.google.com/p/v8/source/detail?r=3995) introduce performance
regression for the case when arrat size is small (think new Array(4)).

It turns out that in those cases rep stos is slower than plain loop (apprently
due to ecx increment, but I didn't check this hypothesis.)  The next thing
to try could be direct jump into right place of long sequence of stos'es.

Committed: http://code.google.com/p/v8/source/detail?r=4664

[antonm, 2010-05-14 12:11:29]

Mads,

may you have a look?

[Mads Ager (chromium), 2010-05-17 09:29:40]

LGTM

http://codereview.chromium.org/2082006/diff/1/4
File src/ia32/builtins-ia32.cc (right):

http://codereview.chromium.org/2082006/diff/1/4#newcode870
src/ia32/builtins-ia32.cc:870: __ cmp(ecx, 16);
Please add a named constant for this.

[antonm, 2010-05-17 14:08:24]

Thanks a lot for review, Mads, submitting.

http://codereview.chromium.org/2082006/diff/1/4
File src/ia32/builtins-ia32.cc (right):

http://codereview.chromium.org/2082006/diff/1/4#newcode870
src/ia32/builtins-ia32.cc:870: __ cmp(ecx, 16);
On 2010/05/17 09:29:40, Mads Ager wrote:
> Please add a named constant for this.

Done.