[turbofan] Introduce CheckString simplified operator.

[turbofan] Introduce CheckString simplified operator.

Introduce the CheckString during native context specialization when we
have string map feedback on a LOAD_IC/STORE_IC. The CheckString
operator, just like its CheckNumber pendant, renames the input and
assigns a proper type, which we will use soon to lower access operations
on Strings, i.e. charCodeAt calls or keyed accesses.

R=jarin@chromium.org
BUG=v8:4930, v8:5141
Committed: https://crrev.com/3deb71fbad8dd61cd335d5801fe176101d2e5283
Cr-Commit-Position: refs/heads/master@{#38076}

[Benedikt Meurer, 2016-07-27 03:47:34]

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

[commit-bot: I haz the power, 2016-07-27 03:47:42]

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

[Benedikt Meurer, 2016-07-27 04:02:27]

Hey Jaro,

Here's a preparation work for optimizing string access.
Please take a look.

Thanks,
Benedikt

[Jarin, 2016-07-27 04:13:00]

lgtm

[Benedikt Meurer, 2016-07-27 04:13:56]

The CQ bit was unchecked by bmeurer@chromium.org

[Benedikt Meurer, 2016-07-27 04:14:00]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-07-27 04:14:09]

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, 2016-07-27 04:15:42]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-27 04:16:38]

Description was changed from

==========
[turbofan] Introduce CheckString simplified operator.

Introduce the CheckString during native context specialization when we
have string map feedback on a LOAD_IC/STORE_IC. The CheckString
operator, just like its CheckNumber pendant, renames the input and
assigns a proper type, which we will use soon to lower access operations
on Strings, i.e. charCodeAt calls or keyed accesses.

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

to

==========
[turbofan] Introduce CheckString simplified operator.

Introduce the CheckString during native context specialization when we
have string map feedback on a LOAD_IC/STORE_IC. The CheckString
operator, just like its CheckNumber pendant, renames the input and
assigns a proper type, which we will use soon to lower access operations
on Strings, i.e. charCodeAt calls or keyed accesses.

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

Committed: https://crrev.com/3deb71fbad8dd61cd335d5801fe176101d2e5283
Cr-Commit-Position: refs/heads/master@{#38076}
==========

[commit-bot: I haz the power, 2016-07-27 04:16:39]

Patchset 1 (id:??) landed as
https://crrev.com/3deb71fbad8dd61cd335d5801fe176101d2e5283
Cr-Commit-Position: refs/heads/master@{#38076}