[stubs] KeyedLoadIC_Megamorphic: use stub cache lookup as fallback

[stubs] KeyedLoadIC_Megamorphic: use stub cache lookup as fallback

When the inline lookup on a fast-property receiver doesn't find anything,
try a stub cache lookup before going into the runtime. This is much
faster for properties loaded from the receiver's prototype chain.

BUG=chromium:650236
Committed: https://crrev.com/b15dd963a359b8cff201d4c8e6f1ca3de7383c2b
Cr-Commit-Position: refs/heads/master@{#39813}

[Jakob Kummerow, 2016-09-26 22:18:03]

jkummerow@chromium.org changed reviewers:
+ ishell@chromium.org

[Jakob Kummerow, 2016-09-26 22:18:03]

PTAL. This should repair the regression on test/js-perf-tests/Iterators/ForOf.

Of course, we can consider doing inline on-prototype lookups in the stub in the
future, but it's a tradeoff: the stub cache is faster when it hits, dynamic
lookups are faster when the cache misses...

[Igor Sheludko, 2016-09-27 06:50:19]

lgtm

[Jakob Kummerow, 2016-09-28 08:40:14]

The CQ bit was checked by jkummerow@chromium.org

[commit-bot: I haz the power, 2016-09-28 08:40:17]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-28 09:05:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-28 09:05:28]

Description was changed from

==========
[stubs] KeyedLoadIC_Megamorphic: use stub cache lookup as fallback

When the inline lookup on a fast-property receiver doesn't find anything,
try a stub cache lookup before going into the runtime. This is much
faster for properties loaded from the receiver's prototype chain.

BUG=chromium:650236
==========

to

==========
[stubs] KeyedLoadIC_Megamorphic: use stub cache lookup as fallback

When the inline lookup on a fast-property receiver doesn't find anything,
try a stub cache lookup before going into the runtime. This is much
faster for properties loaded from the receiver's prototype chain.

BUG=chromium:650236

Committed: https://crrev.com/b15dd963a359b8cff201d4c8e6f1ca3de7383c2b
Cr-Commit-Position: refs/heads/master@{#39813}
==========

[commit-bot: I haz the power, 2016-09-28 09:05:29]

Patchset 1 (id:??) landed as
https://crrev.com/b15dd963a359b8cff201d4c8e6f1ca3de7383c2b
Cr-Commit-Position: refs/heads/master@{#39813}