[turbofan] Lower ConsString creation in JSTypedLowering.

[turbofan] Lower ConsString creation in JSTypedLowering.

Extract String feedback on Add operation and utilize to lower ConsString
creation in JSTypedLowering when we know that a String addition will
definitely result in the creation of a ConsString.

Note that Crankshaft has to guard the potential length overflow of the
resulting string with an eager deoptimization exit, while we can safely
throw an exception in that case.

Also note that the bytecode pipeline does not currently provide the
String feedback for the addition, which has to be added.

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

Committed: https://crrev.com/29dd7fc5ed2490947bd951efa7d49e54c41dfbdc
Cr-Commit-Position: refs/heads/master@{#39540}

[Benedikt Meurer, 2016-09-20 09:37:59]

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

[commit-bot: I haz the power, 2016-09-20 09:38:22]

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, 2016-09-20 10:24:36]

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

[commit-bot: I haz the power, 2016-09-20 10:24:37]

Dry run: This issue passed the CQ dry run.

[Jarin, 2016-09-20 10:27:05]

lgtm (once the redundant store is removed)

https://codereview.chromium.org/2354853002/diff/1/src/compiler/js-typed-lower...
File src/compiler/js-typed-lowering.cc (right):

https://codereview.chromium.org/2354853002/diff/1/src/compiler/js-typed-lower...
src/compiler/js-typed-lowering.cc:80: bool ShouldCreateConsString() {
ShouldCreateConsString -> WillCreateConsString?

https://codereview.chromium.org/2354853002/diff/1/src/compiler/js-typed-lower...
src/compiler/js-typed-lowering.cc:678: effect, control);
Redundant store?

[Benedikt Meurer, 2016-09-20 10:28:29]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2016-09-20 10:28:29]

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/2354853002/#ps20001
(title: "Address feedback.")

[commit-bot: I haz the power, 2016-09-20 10:28:38]

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

[Benedikt Meurer, 2016-09-20 10:40:02]

https://codereview.chromium.org/2354853002/diff/1/src/compiler/js-typed-lower...
File src/compiler/js-typed-lowering.cc (right):

https://codereview.chromium.org/2354853002/diff/1/src/compiler/js-typed-lower...
src/compiler/js-typed-lowering.cc:678: effect, control);
On 2016/09/20 10:27:04, Jarin wrote:
> Redundant store?

Done.

[commit-bot: I haz the power, 2016-09-20 11:00:23]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-09-20 11:05:07]

Description was changed from

==========
[turbofan] Lower ConsString creation in JSTypedLowering.

Extract String feedback on Add operation and utilize to lower ConsString
creation in JSTypedLowering when we know that a String addition will
definitely result in the creation of a ConsString.

Note that Crankshaft has to guard the potential length overflow of the
resulting string with an eager deoptimization exit, while we can safely
throw an exception in that case.

Also note that the bytecode pipeline does not currently provide the
String feedback for the addition, which has to be added.

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

to

==========
[turbofan] Lower ConsString creation in JSTypedLowering.

Extract String feedback on Add operation and utilize to lower ConsString
creation in JSTypedLowering when we know that a String addition will
definitely result in the creation of a ConsString.

Note that Crankshaft has to guard the potential length overflow of the
resulting string with an eager deoptimization exit, while we can safely
throw an exception in that case.

Also note that the bytecode pipeline does not currently provide the
String feedback for the addition, which has to be added.

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

Committed: https://crrev.com/29dd7fc5ed2490947bd951efa7d49e54c41dfbdc
Cr-Commit-Position: refs/heads/master@{#39540}
==========

[commit-bot: I haz the power, 2016-09-20 11:06:33]

Patchset 2 (id:??) landed as
https://crrev.com/29dd7fc5ed2490947bd951efa7d49e54c41dfbdc
Cr-Commit-Position: refs/heads/master@{#39540}