[stubs] Micro optimizations to CodeAssember's allocation path

[stubs] Micro optimizations to CodeAssember's allocation path

Now that the GC team has landed the appropriate changes to ensure that the top
page of the address space is never used for allocation, the inlined fast-case
allocation path in the CodeAssembler can be micro-optimized to an add to top
followed by an unsigned compare to limit, eliding a no-longer-needed overflow
check.

Committed: https://crrev.com/757d82eec5d27f5bf320d857f02e2fb27af6aa63
Cr-Commit-Position: refs/heads/master@{#35830}

[danno, 2016-04-27 12:27:02]

danno@chromium.org changed reviewers:
+ bmeurer@chromium.org, epertoso@chromium.org

[danno, 2016-04-27 12:27:02]

PTAL

[Benedikt Meurer, 2016-04-27 17:41:32]

lgtm

[danno, 2016-04-27 17:42:15]

The CQ bit was checked by danno@chromium.org

[commit-bot: I haz the power, 2016-04-27 17:42:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1923803003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1923803003/1

[commit-bot: I haz the power, 2016-04-27 17:44:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-01 22:01:21]

Description was changed from

==========
[stubs] Micro optimizations to CodeAssember's allocation path

Now that the GC team has landed the appropriate changes to ensure that the top
page of the address space is never used for allocation, the inlined fast-case
allocation path in the CodeAssembler can be micro-optimized to an add to top
followed by an unsigned compare to limit, eliding a no-longer-needed overflow
check.
==========

to

==========
[stubs] Micro optimizations to CodeAssember's allocation path

Now that the GC team has landed the appropriate changes to ensure that the top
page of the address space is never used for allocation, the inlined fast-case
allocation path in the CodeAssembler can be micro-optimized to an add to top
followed by an unsigned compare to limit, eliding a no-longer-needed overflow
check.

Committed: https://crrev.com/757d82eec5d27f5bf320d857f02e2fb27af6aa63
Cr-Commit-Position: refs/heads/master@{#35830}
==========

[commit-bot: I haz the power, 2016-05-01 22:01:22]

Patchset 1 (id:??) landed as
https://crrev.com/757d82eec5d27f5bf320d857f02e2fb27af6aa63
Cr-Commit-Position: refs/heads/master@{#35830}