dart2js: Redo known-type analysis after load-elimination

dart2js: Redo known-type analysis after load-elimination

Code like

  if (this.field is X) {
    (this.field as X)...
  }

after GVN and/or load-elimination becomes

  t1 = this.field;
  if (t1 is X) {
    (t1 as X)...
  }

so it is worth redoing the analysis that allows the elimination of
guaranteed-to-succeed 'as' check.  About 5% of the as-checks in a
large app are optimized out with this change.

R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/8b1f285c69e927146259adcaadb07e36d3829d44

[sra1, 2017-01-24 01:07:59]

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

[sra1, 2017-01-24 01:08:00]

I'll commit after the 1.22 branch.

[Siggi Cherem (dart-lang), 2017-01-24 15:33:00]

lgtm

[sra1, 2017-01-27 18:54:08]

Description was changed from

==========
dart2js: Redo known-type analysis after load-elimination

Code like

  if (this.field is X) {
    (this.field as X)...
  }

after GVN and/or load-elimination becomes

  t1 = this.field;
  if (t1 is X) {
    (t1 as X)...
  }

so it is worth redoing the analysis that allows the elimination of
guaranteed-to-succeed 'as' check.  About 5% of the as-checks in a
large app are optimized out with this change.
==========

to

==========
dart2js: Redo known-type analysis after load-elimination

Code like

  if (this.field is X) {
    (this.field as X)...
  }

after GVN and/or load-elimination becomes

  t1 = this.field;
  if (t1 is X) {
    (t1 as X)...
  }

so it is worth redoing the analysis that allows the elimination of
guaranteed-to-succeed 'as' check.  About 5% of the as-checks in a
large app are optimized out with this change.

R=sigmund@google.com

Committed:
https://github.com/dart-lang/sdk/commit/8b1f285c69e927146259adcaadb07e36d3829d44
==========

[sra1, 2017-01-27 18:54:09]

Committed patchset #2 (id:20001) manually as
8b1f285c69e927146259adcaadb07e36d3829d44 (presubmit successful).