[turbofan] Eliminate a few redundant bounds checks.

[turbofan] Eliminate a few redundant bounds checks.

Usually loops run from 0 to some array length l, which means the
induction variable i will probably have type Unsigned32, just like
the length l. The CheckBounds operation lowers to an Uint32LessThan
comparison, so if we also lower the user level i < l comparison to
Uint32LessThan (whenever possible), we get some bounds check elimination
for free (via value numbering plus branch condition elimination).

This merges the branch condition elimination phase with the late
optimization phase to make this magic happen.

R=jarin@chromium.org
BUG=v8:4930, v8:5141
Committed: https://crrev.com/4f97632880d38a0e1b29f4ce4b468457fc2d82f3
Cr-Commit-Position: refs/heads/master@{#37629}

[Benedikt Meurer, 2016-07-11 07:38:09]

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

[commit-bot: I haz the power, 2016-07-11 07:38:21]

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

[Benedikt Meurer, 2016-07-11 07:39:03]

Hey Jaro,

Here's the rearrangement for some free bounds check elimination.
Please take a look.

Thanks,
Benedikt

[Jarin, 2016-07-11 07:40:03]

lgtm

[Benedikt Meurer, 2016-07-11 07:40:37]

The CQ bit was unchecked by bmeurer@chromium.org

[Benedikt Meurer, 2016-07-11 07:40:41]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-07-11 07:40:53]

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, 2016-07-11 07:56:01]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-11 07:56:02]

Try jobs failed on following builders:
  v8_linux64_avx2_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng/buil...)
  v8_linux64_avx2_rel_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng_trig...)
  v8_mac_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_mac_rel_ng/builds/4719)
  v8_mac_rel_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_mac_rel_ng_triggered/bui...)

[Benedikt Meurer, 2016-07-11 08:15:08]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2016-07-11 08:15:09]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org
Link to the patchset: https://codereview.chromium.org/2135123002/#ps20001
(title: "Fix BranchElimination to play well with the other reducers.")

[commit-bot: I haz the power, 2016-07-11 08:15:19]

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, 2016-07-11 08:40:22]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-07-11 08:40:24]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-11 08:41:10]

Description was changed from

==========
[turbofan] Eliminate a few redundant bounds checks.

Usually loops run from 0 to some array length l, which means the
induction variable i will probably have type Unsigned32, just like
the length l. The CheckBounds operation lowers to an Uint32LessThan
comparison, so if we also lower the user level i < l comparison to
Uint32LessThan (whenever possible), we get some bounds check elimination
for free (via value numbering plus branch condition elimination).

This merges the branch condition elimination phase with the late
optimization phase to make this magic happen.

R=jarin@chromium.org
BUG=v8:4930,v8:5141
==========

to

==========
[turbofan] Eliminate a few redundant bounds checks.

Usually loops run from 0 to some array length l, which means the
induction variable i will probably have type Unsigned32, just like
the length l. The CheckBounds operation lowers to an Uint32LessThan
comparison, so if we also lower the user level i < l comparison to
Uint32LessThan (whenever possible), we get some bounds check elimination
for free (via value numbering plus branch condition elimination).

This merges the branch condition elimination phase with the late
optimization phase to make this magic happen.

R=jarin@chromium.org
BUG=v8:4930,v8:5141

Committed: https://crrev.com/4f97632880d38a0e1b29f4ce4b468457fc2d82f3
Cr-Commit-Position: refs/heads/master@{#37629}
==========

[commit-bot: I haz the power, 2016-07-11 08:41:11]

Patchset 2 (id:??) landed as
https://crrev.com/4f97632880d38a0e1b29f4ce4b468457fc2d82f3
Cr-Commit-Position: refs/heads/master@{#37629}