[crankshaft] Re-add fast-case for string add left/right.

[crankshaft] Re-add fast-case for string add left/right.

Now the StringAddStub can optionally convert it's parameters to strings
(following the rules for the addition operator). This could be further
optimized once we have a ToPrimitiveStub, but it should be sufficient
for the moment.

Also removed the unused Strength parameter to the HStringAdd operator,
because string addition does not depend on language mode.

R=jarin@chromium.org
BUG=v8:4307, chromium:532524
LOG=n

Committed: https://crrev.com/d261849e53fbf8c36efae42d478271f87acff70f
Cr-Commit-Position: refs/heads/master@{#30726}

Committed: https://crrev.com/4542a2d4cc2866a8097d10f11768683bc5ccb224
Cr-Commit-Position: refs/heads/master@{#30858}

[Benedikt Meurer, 2015-09-14 12:30:47]

Hey Michi,

Here's some initial mitigation for the STRING_ADD_LEFT/RIGHT
removal. We can get a lot more out of that, once we have a
ToPrimitiveStub and some bits on Map/PrototypeInfo that tell
you what ToPrimitive will do (i.e. whether @@toPrimitive is
present, and whether valueOf/toString are default implementations).

Please take a look.

Thanks,
Benedikt

[Benedikt Meurer, 2015-09-15 04:37:55]

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

[commit-bot: I haz the power, 2015-09-15 04:38:00]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339053002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339053002/1

[commit-bot: I haz the power, 2015-09-15 04:39:51]

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

[commit-bot: I haz the power, 2015-09-15 04:39:51]

Dry run: This issue passed the CQ dry run.

[Benedikt Meurer, 2015-09-15 04:40:57]

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

[commit-bot: I haz the power, 2015-09-15 04:41:10]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339053002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339053002/1

[Jarin, 2015-09-15 05:41:51]

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

[Jarin, 2015-09-15 05:41:52]

lgtm

[Benedikt Meurer, 2015-09-15 05:42:02]

The CQ bit was unchecked by bmeurer@chromium.org

[Benedikt Meurer, 2015-09-15 05:42:06]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-09-15 05:42:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339053002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339053002/1

[commit-bot: I haz the power, 2015-09-15 06:00:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-15 06:01:02]

Patchset 1 (id:??) landed as
https://crrev.com/d261849e53fbf8c36efae42d478271f87acff70f
Cr-Commit-Position: refs/heads/master@{#30726}

[Michael Achenbach, 2015-09-15 06:40:19]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1347473003/ by machenbach@chromium.org.

The reason for reverting is: [Sheriff] Fails mozilla with deadcode:
http://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20deadcode/buil....

[Benedikt Meurer, 2015-09-15 07:02:02]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-09-15 07:02:03]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org
Link to the patchset: https://codereview.chromium.org/1339053002/#ps20001
(title: "HStringAdd with conversion must not be deletable.")

[commit-bot: I haz the power, 2015-09-15 07:02:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339053002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339053002/20001

[commit-bot: I haz the power, 2015-09-15 07:16:02]

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

[commit-bot: I haz the power, 2015-09-15 07:16:03]

Try jobs failed on following builders:
  v8_linux_arm64_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm64_rel/builds/9590)

[Benedikt Meurer, 2015-09-22 05:22:07]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-09-22 05:22:07]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org
Link to the patchset: https://codereview.chromium.org/1339053002/#ps40001
(title: "REBASE. Real fix for HStringAdd")

[commit-bot: I haz the power, 2015-09-22 05:22:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339053002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339053002/40001

[Benedikt Meurer, 2015-09-22 05:22:59]

The CQ bit was unchecked by bmeurer@chromium.org

[Benedikt Meurer, 2015-09-22 05:27:21]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-09-22 05:27:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339053002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339053002/40001

[commit-bot: I haz the power, 2015-09-22 05:46:42]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-09-22 05:46:57]

Patchset 3 (id:??) landed as
https://crrev.com/4542a2d4cc2866a8097d10f11768683bc5ccb224
Cr-Commit-Position: refs/heads/master@{#30858}