[turbofan] Use CheckMaps for the COW check on elements.

[turbofan] Use CheckMaps for the COW check on elements.

Use a single CheckMaps node instead of the sequence of LoadField,
ReferenceEqual and CheckIf. This also makes it easier to eliminate
the COW check if there are multiple of them in a row.

R=yangguo@chromium.org

Committed: https://crrev.com/887583a15a37bc0d012affb54270bbe8b91185c8
Cr-Commit-Position: refs/heads/master@{#38321}

[Benedikt Meurer, 2016-08-04 05:47:34]

The CQ bit was checked by bmeurer@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-04 05:47:41]

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

[Yang, 2016-08-04 05:50:46]

lgtm

[Benedikt Meurer, 2016-08-04 05:50:56]

The CQ bit was unchecked by bmeurer@chromium.org

[Benedikt Meurer, 2016-08-04 05:51:03]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-08-04 05:51:06]

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, 2016-08-04 06:07:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-04 06:07:39]

Description was changed from

==========
[turbofan] Use CheckMaps for the COW check on elements.

Use a single CheckMaps node instead of the sequence of LoadField,
ReferenceEqual and CheckIf. This also makes it easier to eliminate
the COW check if there are multiple of them in a row.

R=yangguo@chromium.org
==========

to

==========
[turbofan] Use CheckMaps for the COW check on elements.

Use a single CheckMaps node instead of the sequence of LoadField,
ReferenceEqual and CheckIf. This also makes it easier to eliminate
the COW check if there are multiple of them in a row.

R=yangguo@chromium.org

Committed: https://crrev.com/887583a15a37bc0d012affb54270bbe8b91185c8
Cr-Commit-Position: refs/heads/master@{#38321}
==========

[commit-bot: I haz the power, 2016-08-04 06:07:40]

Patchset 1 (id:??) landed as
https://crrev.com/887583a15a37bc0d012affb54270bbe8b91185c8
Cr-Commit-Position: refs/heads/master@{#38321}