Improve fast to slow elements conversion:

Improve fast to slow elements conversion:

o Use a more strict limit for old arrays.

o Initial capacity of a slow elements dictionary should be the number
  of used elements and not the old array capacity.


R=danno@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=8744

[danno, 2011-07-22 09:21:25]

LGTM if you address my comment.

http://codereview.chromium.org/7464032/diff/1001/src/objects.cc
File src/objects.cc (right):

http://codereview.chromium.org/7464032/diff/1001/src/objects.cc#newcode9138
src/objects.cc:9138: kind <= LAST_EXTERNAL_ARRAY_ELEMENTS_KIND);
Please leave this explicitly enumerated and remove the default so that when we
add the next elements kind the compiler notices that the enum is missing. With
the default, errors like this are harder to catch.

[Vitaly Repeshko, 2011-07-25 15:50:55]

I addressed the feedback and I changed the heuristic to be more clearly
expressed in terms of backing storage memory usage. Please take another look.


Thanks,
Vitaly

http://codereview.chromium.org/7464032/diff/1001/src/objects.cc
File src/objects.cc (right):

http://codereview.chromium.org/7464032/diff/1001/src/objects.cc#newcode9138
src/objects.cc:9138: kind <= LAST_EXTERNAL_ARRAY_ELEMENTS_KIND);
On 2011/07/22 09:21:25, danno wrote:
> Please leave this explicitly enumerated and remove the default so that when we
> add the next elements kind the compiler notices that the enum is missing. With
> the default, errors like this are harder to catch.

Agreed. I added the external array cases back. They always return the actual
capacity and 100% usage.

[danno, 2011-07-26 13:06:45]

LGTM. I like it. It cleans up a few things that were a bit misleading/difficult
to understand.