[turbofan] Teach ad-hoc load elimination about atomic regions.

[turbofan] Teach ad-hoc load elimination about atomic regions.

The LoadElimination in TurboFan can look into the atomic regions and
elimination subsequent loads based on stores/allocations in that atomic
regions.

R=jarin@chromium.org

Committed: https://crrev.com/902f264a5725b3563a6a4aca3cea9dc59db0d92d
Cr-Commit-Position: refs/heads/master@{#32179}

[Benedikt Meurer, 2015-11-23 14:10:00]

Hey Jaro,

We talked about this earlier, that the load elimination should be able to look
into atomic regions. This is a fairly simple patch to do that.
Please take a look.

Thanks,
Benedikt

[Jarin, 2015-11-23 14:13:44]

lgtm

[Benedikt Meurer, 2015-11-23 14:32:46]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-11-23 14:32:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1472703005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1472703005/1

[commit-bot: I haz the power, 2015-11-23 14:43:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-23 14:44:03]

Patchset 1 (id:??) landed as
https://crrev.com/902f264a5725b3563a6a4aca3cea9dc59db0d92d
Cr-Commit-Position: refs/heads/master@{#32179}