Mark some string operations as GVN-able.

Mark some string operations as GVN-able.

There are not many GVN optimizations, but knowing the calls are effect-free allows some fields to be load-eliminated, leading to the loaded value having a refined type. In a big app, about 20 calls to String.substring no longer need an interceptor.

R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/a608c592fd41eed5288109358726605e6942b2c5

[sra1, 2017-01-11 22:37:03]

sra@google.com changed reviewers:
+ sigmund@google.com

[Siggi Cherem (dart-lang), 2017-01-11 22:40:05]

lgtm

[sra1, 2017-01-12 03:51:57]

Description was changed from

==========
Mark some string operations as GVN-able.

There are not many GVN optimizations, but knowing the calls are effect-free
allows some fields to be load-eliminated, leading to the loaded value having a
refined type. In a big app, about 20 calls to String.substring no longer need an
interceptor.
==========

to

==========
Mark some string operations as GVN-able.

There are not many GVN optimizations, but knowing the calls are effect-free
allows some fields to be load-eliminated, leading to the loaded value having a
refined type. In a big app, about 20 calls to String.substring no longer need an
interceptor.

R=sigmund@google.com

Committed:
https://github.com/dart-lang/sdk/commit/a608c592fd41eed5288109358726605e6942b2c5
==========

[sra1, 2017-01-12 03:51:57]

Committed patchset #3 (id:40001) manually as
a608c592fd41eed5288109358726605e6942b2c5 (presubmit successful).