Retain maps embedded in optimized code for several garbage collections.

Retain maps embedded in optimized code for several garbage collections.

This keeps dying maps alive for FLAG_retain_maps_for_n_gc garbage collections
to increase chances of them being reused for new objects in future and
decrease number of deoptimizations.

BUG=v8:3664
LOG=N
TEST=cctest/test-heap/MapRetaining

Committed: https://crrev.com/1b00451f5748ece669127ce9986ad77e4285bdad
Cr-Commit-Position: refs/heads/master@{#27040}

[ulan, 2015-03-05 12:46:08]

ulan@chromium.org changed reviewers:
+ hpayer@chromium.org

[ulan, 2015-03-05 12:46:09]

PTAL. This relands parts of CL 794583003. The difference is that we retain only
maps embedded in optimized code, which avoid maps space iteration.

[Hannes Payer (out of office), 2015-03-05 21:12:28]

One nit and please look into the try bot failures. LGTM

https://codereview.chromium.org/980523004/diff/40001/src/objects-inl.h
File src/objects-inl.h (right):

https://codereview.chromium.org/980523004/diff/40001/src/objects-inl.h#newcod...
src/objects-inl.h:2406: 
Should we DCHECK for wrong input values? Negative values? The index should be
unsigned. I know, the functions above are similar'ish... As you like.

[ulan, 2015-03-06 10:16:34]

Thanks! I fixed bot failure.

https://codereview.chromium.org/980523004/diff/40001/src/objects-inl.h
File src/objects-inl.h (right):

https://codereview.chromium.org/980523004/diff/40001/src/objects-inl.h#newcod...
src/objects-inl.h:2406: 
On 2015/03/05 21:12:28, Hannes Payer wrote:
> Should we DCHECK for wrong input values? Negative values? The index should be
> unsigned. I know, the functions above are similar'ish... As you like.

Fixed array getters and setters check the index.

[ulan, 2015-03-06 12:04:34]

The CQ bit was checked by ulan@chromium.org

[ulan, 2015-03-06 12:04:34]

The patchset sent to the CQ was uploaded after l-g-t-m from hpayer@chromium.org
Link to the patchset: https://codereview.chromium.org/980523004/#ps80002 (title:
"Check constructor.")

[commit-bot: I haz the power, 2015-03-06 12:05:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/980523004/80002

[commit-bot: I haz the power, 2015-03-06 12:36:25]

Committed patchset #6 (id:80002)

[commit-bot: I haz the power, 2015-03-06 12:36:43]

Patchset 6 (id:??) landed as
https://crrev.com/1b00451f5748ece669127ce9986ad77e4285bdad
Cr-Commit-Position: refs/heads/master@{#27040}