dart2js cps: More rewritings for compound assignments.

dart2js cps: More rewritings for compound assignments.

Compound assignments are now generated for:

- SetStatic, previously only supported for SetField, SetIndex, and
  variable uses.

- SetField and SetIndex when the receiver is 'this', previously only
  supported for variable uses.

- String concatenation with >2 arguments, previously only supported
  with exactly 2 arguments.

BUG=
R=sra@google.com

Committed: https://github.com/dart-lang/sdk/commit/762c41f9e49d56846f9c67cce300f92308a6b7aa

[asgerf, 2016-01-21 22:44:23]

Description was changed from

==========
dart2js cps: More rewritings for conditional and compound assignments.

Exract SetStatic, SetField, SetIndex from conditional expression, e.g:

	COND ? this.field = A : this.field = B
		==>
	this.field = COND ? A : B;

previously the above only worked for locals.

Support compounds for SetStatic, previously only supported for SetField,
SetIndex, and variable uses.

Support compounds SetField and SetIndex when the receiver is 'this',
previously only supported for variable uses.

Support compounds for string concatenation with >2 arguments, previously
supported with exactly 2 arguments.

BUG=
==========

to

==========
dart2js cps: More rewritings for conditional and compound assignments.

Exract SetStatic, SetField, SetIndex from conditional expression, e.g:

	COND ? this.field = A : this.field = B
		==>
	this.field = COND ? A : B;

previously the above only worked for locals.

Support compounds for SetStatic, previously only supported for SetField,
SetIndex, and variable uses.

Support compounds SetField and SetIndex when the receiver is 'this',
previously only supported for variable uses.

Support compounds for string concatenation with >2 arguments, previously
only supported with exactly 2 arguments.

BUG=
==========

[asgerf, 2016-01-21 22:45:18]

asgerf@google.com changed reviewers:
+ kmillikin@google.com, sra@google.com

[asgerf, 2016-01-21 22:45:18]

Not a big impact, just some missing redexes that were bothering me.

[sra1, 2016-01-22 03:22:04]

LGTM!

Most of the differences I see are of the form

    ++this.field;

I suggest landing this separately.

https://codereview.chromium.org/1613853003/diff/1/pkg/compiler/lib/src/tree_i...
File pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart (right):

https://codereview.chromium.org/1613853003/diff/1/pkg/compiler/lib/src/tree_i...
pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart:1328: /// a
single assignment of form `v := combine(E1, E2)`.
We probably want to avoid this where one arm is a constant that the JS VM can
tell does not need a write-barrier.

[asgerf, 2016-01-22 18:49:23]

Description was changed from

==========
dart2js cps: More rewritings for conditional and compound assignments.

Exract SetStatic, SetField, SetIndex from conditional expression, e.g:

	COND ? this.field = A : this.field = B
		==>
	this.field = COND ? A : B;

previously the above only worked for locals.

Support compounds for SetStatic, previously only supported for SetField,
SetIndex, and variable uses.

Support compounds SetField and SetIndex when the receiver is 'this',
previously only supported for variable uses.

Support compounds for string concatenation with >2 arguments, previously
only supported with exactly 2 arguments.

BUG=
==========

to

==========
dart2js cps: More rewritings for compound assignments.

Compound assignment are now generated for:

- SetStatic, previously only supported for SetField, SetIndex, and
  variable uses.

- SetField and SetIndex when the receiver is 'this', previously only
  supported for variable uses.

- String concatenation with >2 arguments, previously only supported
  with exactly 2 arguments.

BUG=
==========

[asgerf, 2016-01-22 18:49:56]

Description was changed from

==========
dart2js cps: More rewritings for compound assignments.

Compound assignment are now generated for:

- SetStatic, previously only supported for SetField, SetIndex, and
  variable uses.

- SetField and SetIndex when the receiver is 'this', previously only
  supported for variable uses.

- String concatenation with >2 arguments, previously only supported
  with exactly 2 arguments.

BUG=
==========

to

==========
dart2js cps: More rewritings for compound assignments.

Compound assignments are now generated for:

- SetStatic, previously only supported for SetField, SetIndex, and
  variable uses.

- SetField and SetIndex when the receiver is 'this', previously only
  supported for variable uses.

- String concatenation with >2 arguments, previously only supported
  with exactly 2 arguments.

BUG=
==========

[asgerf, 2016-01-22 18:54:47]

As you suggested, I am changing this CL to only contain the changes to compound
assignments.

https://codereview.chromium.org/1613853003/diff/1/pkg/compiler/lib/src/tree_i...
File pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart (right):

https://codereview.chromium.org/1613853003/diff/1/pkg/compiler/lib/src/tree_i...
pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart:1328: /// a
single assignment of form `v := combine(E1, E2)`.
On 2016/01/22 03:22:04, sra1 wrote:
> We probably want to avoid this where one arm is a constant that the JS VM can
> tell does not need a write-barrier. 

Good point.  I looked at the IR generated by V8 in the two cases and it does
indeed hit a write-barrier it would not hit otherwise.

[asgerf, 2016-01-22 19:22:07]

Description was changed from

==========
dart2js cps: More rewritings for compound assignments.

Compound assignments are now generated for:

- SetStatic, previously only supported for SetField, SetIndex, and
  variable uses.

- SetField and SetIndex when the receiver is 'this', previously only
  supported for variable uses.

- String concatenation with >2 arguments, previously only supported
  with exactly 2 arguments.

BUG=
==========

to

==========
dart2js cps: More rewritings for compound assignments.

Compound assignments are now generated for:

- SetStatic, previously only supported for SetField, SetIndex, and
  variable uses.

- SetField and SetIndex when the receiver is 'this', previously only
  supported for variable uses.

- String concatenation with >2 arguments, previously only supported
  with exactly 2 arguments.

BUG=
R=sra@google.com

Committed:
https://github.com/dart-lang/sdk/commit/762c41f9e49d56846f9c67cce300f92308a6b7aa
==========

[asgerf, 2016-01-22 19:22:08]

Committed patchset #3 (id:40001) manually as
762c41f9e49d56846f9c67cce300f92308a6b7aa (presubmit successful).