[turbofan] Add support for keyed access to strings.

[turbofan] Add support for keyed access to strings.

This introduces initial support to handle keyed load access to
String primitives. This is accomplished via the existing operators
StringCharCodeAt and StringFromCharCode, which we already use to
optimize String.prototype.charCodeAt and String.fromCharCode.

R=yangguo@chromium.org
BUG=v8:5267
Committed: https://crrev.com/3909250a6c7ae0003a1d54a3d47ec32260e4ede4
Cr-Commit-Position: refs/heads/master@{#38512}

[Benedikt Meurer, 2016-08-09 18:30:07]

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

[commit-bot: I haz the power, 2016-08-09 18:30:10]

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, 2016-08-09 19:08:02]

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

[commit-bot: I haz the power, 2016-08-09 19:08:03]

Dry run: This issue passed the CQ dry run.

[Toon Verwaest, 2016-08-10 04:31:08]

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

[Toon Verwaest, 2016-08-10 04:31:08]

lgtm. you probably want to clean up that MapList business in the future :)

[Benedikt Meurer, 2016-08-10 04:31:40]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-08-10 04:31:43]

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, 2016-08-10 04:33:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-10 04:33:39]

Description was changed from

==========
[turbofan] Add support for keyed access to strings.

This introduces initial support to handle keyed load access to
String primitives. This is accomplished via the existing operators
StringCharCodeAt and StringFromCharCode, which we already use to
optimize String.prototype.charCodeAt and String.fromCharCode.

R=yangguo@chromium.org
BUG=v8:5267
==========

to

==========
[turbofan] Add support for keyed access to strings.

This introduces initial support to handle keyed load access to
String primitives. This is accomplished via the existing operators
StringCharCodeAt and StringFromCharCode, which we already use to
optimize String.prototype.charCodeAt and String.fromCharCode.

R=yangguo@chromium.org
BUG=v8:5267

Committed: https://crrev.com/3909250a6c7ae0003a1d54a3d47ec32260e4ede4
Cr-Commit-Position: refs/heads/master@{#38512}
==========

[commit-bot: I haz the power, 2016-08-10 04:33:40]

Patchset 1 (id:??) landed as
https://crrev.com/3909250a6c7ae0003a1d54a3d47ec32260e4ede4
Cr-Commit-Position: refs/heads/master@{#38512}