[turbofan] Improve lowering for NumberAbs to Int32Abs.

[turbofan] Improve lowering for NumberAbs to Int32Abs.

We can compute the absolute integer value w/o any conditional execution
by using the bit trick formula

  let sign = input >> 31 in
  (input ^ sign) - sign

which generates fairly decent code on all supported architectures.

R=jarin@chromium.org

Committed: https://crrev.com/085ec5c25f9dd1cc51914d90c3e0aa1c45d002fe
Cr-Commit-Position: refs/heads/master@{#37965}

[Benedikt Meurer, 2016-07-22 03:44:33]

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

[commit-bot: I haz the power, 2016-07-22 03:44:35]

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

[Benedikt Meurer, 2016-07-22 03:56:54]

Hey Jaro,

Here's a better non-branchy version of integer Math.abs.
Please take a look.

Thanks,
Benedikt

[commit-bot: I haz the power, 2016-07-22 04:05:05]

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

[commit-bot: I haz the power, 2016-07-22 04:05:06]

Dry run: This issue passed the CQ dry run.

[Jarin, 2016-07-22 04:31:17]

lgtm

[Benedikt Meurer, 2016-07-22 04:32:27]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-07-22 04:32:32]

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, 2016-07-22 04:33:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-22 04:34:52]

Description was changed from

==========
[turbofan] Improve lowering for NumberAbs to Int32Abs.

We can compute the absolute integer value w/o any conditional execution
by using the bit trick formula

  let sign = input >> 31 in
  (input ^ sign) - sign

which generates fairly decent code on all supported architectures.

R=jarin@chromium.org
==========

to

==========
[turbofan] Improve lowering for NumberAbs to Int32Abs.

We can compute the absolute integer value w/o any conditional execution
by using the bit trick formula

  let sign = input >> 31 in
  (input ^ sign) - sign

which generates fairly decent code on all supported architectures.

R=jarin@chromium.org

Committed: https://crrev.com/085ec5c25f9dd1cc51914d90c3e0aa1c45d002fe
Cr-Commit-Position: refs/heads/master@{#37965}
==========

[commit-bot: I haz the power, 2016-07-22 04:34:53]

Patchset 1 (id:??) landed as
https://crrev.com/085ec5c25f9dd1cc51914d90c3e0aa1c45d002fe
Cr-Commit-Position: refs/heads/master@{#37965}