Rewrite HStringify(a) to a.toString() when guaranteed to return a String

Rewrite HStringify(a) to a.toString() when guaranteed to return a String

BUG=
R=het@google.com

Committed: https://github.com/dart-lang/sdk/commit/a2945cb281518affe109e6a11cba50bb29e19569

[sra1, 2016-09-23 17:37:29]

Patchset #2 (id:20001) has been deleted

[sra1, 2016-09-23 17:37:38]

Patchset #1 (id:1) has been deleted

[sra1, 2016-09-23 17:45:07]

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

[Harry Terkelsen, 2016-09-23 17:49:25]

lgtm

https://codereview.chromium.org/2365493002/diff/40001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/optimize.dart (right):

https://codereview.chromium.org/2365493002/diff/40001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/optimize.dart:1035: HInstruction tryToString() {
Will this only be called in the kernel->ssa case? In the normal case these will
have all been converted already.

[sra1, 2016-09-23 18:15:39]

https://codereview.chromium.org/2365493002/diff/40001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/optimize.dart (right):

https://codereview.chromium.org/2365493002/diff/40001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/optimize.dart:1035: HInstruction tryToString() {
On 2016/09/23 17:49:25, Harry Terkelsen wrote:
> Will this only be called in the kernel->ssa case? In the normal case these
will
> have all been converted already.

There are a few in the old builder case.
There are two reasons - 

1. The builder does not remove useless Phi nodes, so not all are recognized.

2. Optimizations could improve the type (e.g seeing that HStringify(a) is under
'if (a != null)')

[sra1, 2016-09-23 22:30:06]

Description was changed from

==========
Rewrite HStringify(a) to a.toString() when guaranteed to return a String

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

to

==========
Rewrite HStringify(a) to a.toString() when guaranteed to return a String

BUG=
R=het@google.com

Committed:
https://github.com/dart-lang/sdk/commit/a2945cb281518affe109e6a11cba50bb29e19569
==========

[sra1, 2016-09-23 22:30:07]

Committed patchset #1 (id:40001) manually as
a2945cb281518affe109e6a11cba50bb29e19569 (presubmit successful).