[turbofan] Boost performance of Array.prototype.shift by 4x.

[turbofan] Boost performance of Array.prototype.shift by 4x.

For small arrays, it's way faster to just move the elements instead of
doing the fairly complex and heavy-weight left-trimming. Crankshaft has
had this optimization for small arrays already; this CL more or less
ports this functionality to TurboFan, which yields a 4x speed-up when
using shift on small arrays (with up to 16 elements).

This should recover some of the regressions reported in the Node.js issues

  https://github.com/nodejs/node/issues/12657

and discovered for the syncthrough module using

  https://github.com/mcollina/syncthrough/blob/master/benchmarks/basic.js

as benchmark.

R=jarin@chromium.org
BUG=v8:6376
Review-Url: https://codereview.chromium.org/2874453002
Cr-Commit-Position: refs/heads/master@{#45216}
Committed: https://chromium.googlesource.com/v8/v8/+/6d38f89d262a05208002648489daa4ddce44020e

[Benedikt Meurer, 2017-05-09 18:59:02]

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

[commit-bot: I haz the power, 2017-05-09 18:59:10]

Dry run: 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, 2017-05-09 21:10:40]

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

[commit-bot: I haz the power, 2017-05-09 21:10:40]

Dry run: This issue passed the CQ dry run.

[Benedikt Meurer, 2017-05-10 04:57:00]

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

[commit-bot: I haz the power, 2017-05-10 04:57:12]

Dry run: CQ is trying da patch.

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

[Benedikt Meurer, 2017-05-10 04:58:31]

Hey Jaro,

Here's the A.p.shift fix for TurboFan. Please take a look.

Thanks,
Benedikt

[Jarin, 2017-05-10 05:15:39]

lgtm

[commit-bot: I haz the power, 2017-05-10 05:33:18]

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

[commit-bot: I haz the power, 2017-05-10 05:33:19]

Dry run: This issue passed the CQ dry run.

[Benedikt Meurer, 2017-05-10 05:46:36]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2017-05-10 05:46:39]

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, 2017-05-10 05:48:21]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1494395196578400,
"parent_rev": "619dfed4f706e8259802bed0a864c6ed820fda97", "commit_rev":
"6d38f89d262a05208002648489daa4ddce44020e"}

[commit-bot: I haz the power, 2017-05-10 05:48:29]

Description was changed from

==========
[turbofan] Boost performance of Array.prototype.shift by 4x.

For small arrays, it's way faster to just move the elements instead of
doing the fairly complex and heavy-weight left-trimming. Crankshaft has
had this optimization for small arrays already; this CL more or less
ports this functionality to TurboFan, which yields a 4x speed-up when
using shift on small arrays (with up to 16 elements).

This should recover some of the regressions reported in the Node.js issues

  https://github.com/nodejs/node/issues/12657

and discovered for the syncthrough module using

  https://github.com/mcollina/syncthrough/blob/master/benchmarks/basic.js

as benchmark.

R=jarin@chromium.org
BUG=v8:6376
==========

to

==========
[turbofan] Boost performance of Array.prototype.shift by 4x.

For small arrays, it's way faster to just move the elements instead of
doing the fairly complex and heavy-weight left-trimming. Crankshaft has
had this optimization for small arrays already; this CL more or less
ports this functionality to TurboFan, which yields a 4x speed-up when
using shift on small arrays (with up to 16 elements).

This should recover some of the regressions reported in the Node.js issues

  https://github.com/nodejs/node/issues/12657

and discovered for the syncthrough module using

  https://github.com/mcollina/syncthrough/blob/master/benchmarks/basic.js

as benchmark.

R=jarin@chromium.org
BUG=v8:6376

Review-Url: https://codereview.chromium.org/2874453002
Cr-Commit-Position: refs/heads/master@{#45216}
Committed:
https://chromium.googlesource.com/v8/v8/+/6d38f89d262a05208002648489daa4ddce4...
==========

[commit-bot: I haz the power, 2017-05-10 05:48:30]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/v8/v8/+/6d38f89d262a05208002648489daa4ddce4...