Added a DependentCode field to AllocationSite.

Added a DependentCode field to AllocationSite. It's not currently used,
this initial CL is just to get the object layout correct.

BUG=
R=hpayer@chromium.org, mstarzinger@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16833

[mvstanton, 2013-08-27 11:28:48]

Hi guys, taking a "baby step" of adding DependentCode to AllocationSite. Could
you especially scrutinize my approach to making sure a write barrier isn't used
in code-stubs-hydrogen.cc?
Thanks,
--Michael

[Michael Starzinger, 2013-09-19 13:56:17]

LGTM with comments.

https://codereview.chromium.org/23567003/diff/4001/src/code-stubs-hydrogen.cc
File src/code-stubs-hydrogen.cc (right):

https://codereview.chromium.org/23567003/diff/4001/src/code-stubs-hydrogen.cc...
src/code-stubs-hydrogen.cc:481: isolate()->heap()->empty_fixed_array()));
nit: Let's drop this assert, see comment below.

https://codereview.chromium.org/23567003/diff/4001/src/code-stubs-hydrogen.cc...
src/code-stubs-hydrogen.cc:488: store->SkipWriteBarrier();
We should just add the empty fixed array to the list of immortal immovable
objects and not worry about WBs here. The graph builder should not need to think
about WBs.

https://codereview.chromium.org/23567003/diff/4001/src/objects-inl.h
File src/objects-inl.h (right):

https://codereview.chromium.org/23567003/diff/4001/src/objects-inl.h#newcode1324
src/objects-inl.h:1324: 
nit: Two empty newlines.

[Hannes Payer (out of office), 2013-09-19 13:57:08]

LGTM, after talking offline.

https://codereview.chromium.org/23567003/diff/1/src/code-stubs-hydrogen.cc
File src/code-stubs-hydrogen.cc (right):

https://codereview.chromium.org/23567003/diff/1/src/code-stubs-hydrogen.cc#ne...
src/code-stubs-hydrogen.cc:470: isolate()->heap()->empty_fixed_array()));
This assert can go, empty fixed array is always in old space.

https://codereview.chromium.org/23567003/diff/1/src/code-stubs-hydrogen.cc#ne...
src/code-stubs-hydrogen.cc:476: // empty fixed array be an "immortal immovable?"
The write barrier should be skipped there by default. We can verify if you like?

[mvstanton, 2013-09-19 14:06:10]

thx yall, checking in...

https://codereview.chromium.org/23567003/diff/1/src/code-stubs-hydrogen.cc
File src/code-stubs-hydrogen.cc (right):

https://codereview.chromium.org/23567003/diff/1/src/code-stubs-hydrogen.cc#ne...
src/code-stubs-hydrogen.cc:470: isolate()->heap()->empty_fixed_array()));
On 2013/09/19 13:57:08, Hannes Payer wrote:
> This assert can go, empty fixed array is always in old space.

Done.

https://codereview.chromium.org/23567003/diff/1/src/code-stubs-hydrogen.cc#ne...
src/code-stubs-hydrogen.cc:476: // empty fixed array be an "immortal immovable?"
On 2013/09/19 13:57:08, Hannes Payer wrote:
> The write barrier should be skipped there by default. We can verify if you
like?

I did verify, it was there, but now I've added the empty fixed array to the
immortal immovable list, yay! So the SkipWriteBarrier is removed.

https://codereview.chromium.org/23567003/diff/4001/src/code-stubs-hydrogen.cc
File src/code-stubs-hydrogen.cc (right):

https://codereview.chromium.org/23567003/diff/4001/src/code-stubs-hydrogen.cc...
src/code-stubs-hydrogen.cc:481: isolate()->heap()->empty_fixed_array()));
On 2013/09/19 13:56:17, Michael Starzinger wrote:
> nit: Let's drop this assert, see comment below.

Done.

https://codereview.chromium.org/23567003/diff/4001/src/code-stubs-hydrogen.cc...
src/code-stubs-hydrogen.cc:488: store->SkipWriteBarrier();
On 2013/09/19 13:56:17, Michael Starzinger wrote:
> We should just add the empty fixed array to the list of immortal immovable
> objects and not worry about WBs here. The graph builder should not need to
think
> about WBs.

Right on, done!

[mvstanton, 2013-09-19 14:13:45]

Committed patchset #3 manually as r16833 (presubmit successful).