[turbofan] Also constant-fold String element access if possible.

[turbofan] Also constant-fold String element access if possible.

When accessing elements of a compile-time constant String, we don't need
to check the receiver, and we can constant-fold the loading of the
length.

R=yangguo@chromium.org

Committed: https://crrev.com/8e7426173b63a3090b880b7353911d8ba8501a12
Cr-Commit-Position: refs/heads/master@{#40521}

[Benedikt Meurer, 2016-10-24 06:42:45]

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

[commit-bot: I haz the power, 2016-10-24 06:42:46]

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

[Yang, 2016-10-24 06:48:32]

lgtm

https://codereview.chromium.org/2442243002/diff/1/src/compiler/js-native-cont...
File src/compiler/js-native-context-specialization.cc (right):

https://codereview.chromium.org/2442243002/diff/1/src/compiler/js-native-cont...
src/compiler/js-native-context-specialization.cc:687: if (nexus.GetKeyType() ==
ELEMENT) {
So... if the index is also a constant... *wink*

[commit-bot: I haz the power, 2016-10-24 07:12:15]

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

[commit-bot: I haz the power, 2016-10-24 07:12:16]

Dry run: This issue passed the CQ dry run.

[Benedikt Meurer, 2016-10-24 07:34:29]

https://codereview.chromium.org/2442243002/diff/1/src/compiler/js-native-cont...
File src/compiler/js-native-context-specialization.cc (right):

https://codereview.chromium.org/2442243002/diff/1/src/compiler/js-native-cont...
src/compiler/js-native-context-specialization.cc:687: if (nexus.GetKeyType() ==
ELEMENT) {
Follow-up CL.

[Benedikt Meurer, 2016-10-24 07:34:35]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-10-24 07:34:45]

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, 2016-10-24 07:38:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-17 22:10:33]

Description was changed from

==========
[turbofan] Also constant-fold String element access if possible.

When accessing elements of a compile-time constant String, we don't need
to check the receiver, and we can constant-fold the loading of the
length.

R=yangguo@chromium.org
==========

to

==========
[turbofan] Also constant-fold String element access if possible.

When accessing elements of a compile-time constant String, we don't need
to check the receiver, and we can constant-fold the loading of the
length.

R=yangguo@chromium.org

Committed: https://crrev.com/8e7426173b63a3090b880b7353911d8ba8501a12
Cr-Commit-Position: refs/heads/master@{#40521}
==========

[commit-bot: I haz the power, 2016-11-17 22:10:34]

Patchset 1 (id:??) landed as
https://crrev.com/8e7426173b63a3090b880b7353911d8ba8501a12
Cr-Commit-Position: refs/heads/master@{#40521}