Fast-path in SlowFlatten for ConsStrings with empty first part

Fast-path in SlowFlatten for ConsStrings with empty first part

TurboFan can create ConsStrings with empty first parts (for history on
this decision, see da27e0c88602218b3d5bdd6056d705063b1bf792). Add a
fast-path for such cases in String::SlowFlatten.

BUG=

Committed: https://crrev.com/806b350482b7c6423a5bac561a7fa8f55fcc845c
Cr-Commit-Position: refs/heads/master@{#40885}

[jgruber, 2016-11-10 09:29:26]

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

[commit-bot: I haz the power, 2016-11-10 09:29:34]

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, 2016-11-10 09:48:52]

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

[commit-bot: I haz the power, 2016-11-10 09:48:53]

Dry run: Try jobs failed on following builders:
  v8_mac_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_mac_rel_ng/builds/12229)
  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...)

[jgruber, 2016-11-10 10:00:19]

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

[commit-bot: I haz the power, 2016-11-10 10:00:23]

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

[jgruber, 2016-11-10 10:33:18]

jgruber@chromium.org changed reviewers:
+ yangguo@chromium.org

[commit-bot: I haz the power, 2016-11-10 10:33:35]

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

[commit-bot: I haz the power, 2016-11-10 10:33:35]

Dry run: Try jobs failed on following builders:
  v8_linux_dbg_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_dbg_ng/builds/15979)
  v8_linux_dbg_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_dbg_ng_triggered/b...)

[Yang, 2016-11-10 10:34:07]

On 2016/11/10 10:33:19, jgruber wrote:

lgtm.

[Benedikt Meurer, 2016-11-10 10:36:33]

bmeurer@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Benedikt Meurer, 2016-11-10 10:36:34]

LGTM, thanks.

[jgruber, 2016-11-10 10:52:53]

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

[commit-bot: I haz the power, 2016-11-10 10:52:55]

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, 2016-11-10 11:18:36]

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

[commit-bot: I haz the power, 2016-11-10 11:18:37]

Dry run: This issue passed the CQ dry run.

[jgruber, 2016-11-10 11:20:44]

The CQ bit was checked by jgruber@chromium.org

[jgruber, 2016-11-10 11:20:45]

The patchset sent to the CQ was uploaded after l-g-t-m from
bmeurer@chromium.org, yangguo@chromium.org
Link to the patchset: https://codereview.chromium.org/2489273002/#ps40001
(title: "Ensure string length does not change in test")

[commit-bot: I haz the power, 2016-11-10 11:20:53]

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, 2016-11-10 11:23:14]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-11-17 22:28:50]

Description was changed from

==========
Fast-path in SlowFlatten for ConsStrings with empty first part

TurboFan can create ConsStrings with empty first parts (for history on
this decision, see da27e0c88602218b3d5bdd6056d705063b1bf792). Add a
fast-path for such cases in String::SlowFlatten.

BUG=
==========

to

==========
Fast-path in SlowFlatten for ConsStrings with empty first part

TurboFan can create ConsStrings with empty first parts (for history on
this decision, see da27e0c88602218b3d5bdd6056d705063b1bf792). Add a
fast-path for such cases in String::SlowFlatten.

BUG=

Committed: https://crrev.com/806b350482b7c6423a5bac561a7fa8f55fcc845c
Cr-Commit-Position: refs/heads/master@{#40885}
==========

[commit-bot: I haz the power, 2016-11-17 22:28:51]

Patchset 3 (id:??) landed as
https://crrev.com/806b350482b7c6423a5bac561a7fa8f55fcc845c
Cr-Commit-Position: refs/heads/master@{#40885}