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

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

BUG=

Committed: https://github.com/dart-lang/sdk/commit/4867cf9adca793779397e4de068bcddaedba14ff

[sra1, 2017-02-01 00:57:25]

Description was changed from

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

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

to

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

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

[sra1, 2017-02-01 00:57:25]

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

[sra1, 2017-02-01 00:59:15]

https://codereview.chromium.org/2662493004/diff/20001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/codegen.dart (left):

https://codereview.chromium.org/2662493004/diff/20001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/codegen.dart:2853: // sufficient for doing an argument
or receiver check.
I think this is incorrect. The check is Math.floor(x) !== x, which will not
accidentally accept numeric strings.

[sra1, 2017-02-01 00:59:35]

Description was changed from

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

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

to

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

BUG=

Committed:
https://github.com/dart-lang/sdk/commit/4867cf9adca793779397e4de068bcddaedba14ff
==========

[sra1, 2017-02-01 00:59:36]

Committed patchset #2 (id:20001) manually as
4867cf9adca793779397e4de068bcddaedba14ff (presubmit successful).

[Siggi Cherem (dart-lang), 2017-02-01 01:31:48]

https://codereview.chromium.org/2662493004/diff/20001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/codegen.dart (left):

https://codereview.chromium.org/2662493004/diff/20001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/codegen.dart:2853: // sufficient for doing an argument
or receiver check.
On 2017/02/01 00:59:15, sra1 wrote:
> I think this is incorrect. The check is Math.floor(x) !== x, which will not
> accidentally accept numeric strings.

Could we end up hitting the Math.floor case when the input is `null`? which will
say true instead of false? for example if input.isPrimitiveOrNull? 

I'm not as familiar with this as you are, so feel free to ignore and I'll ask
you in person later in the week.

[sra1, 2017-02-01 02:15:47]

https://codereview.chromium.org/2662493004/diff/20001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/codegen.dart (left):

https://codereview.chromium.org/2662493004/diff/20001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/codegen.dart:2853: // sufficient for doing an argument
or receiver check.
On 2017/02/01 01:31:48, Siggi Cherem (dart-lang) wrote:
> On 2017/02/01 00:59:15, sra1 wrote:
> > I think this is incorrect. The check is Math.floor(x) !== x, which will not
> > accidentally accept numeric strings.
> 
> Could we end up hitting the Math.floor case when the input is `null`? which
will
> say true instead of false? for example if input.isPrimitiveOrNull? 
> 
> I'm not as familiar with this as you are, so feel free to ignore and I'll ask
> you in person later in the week.

It works as intended:

  Math.floor(null) --> 0,           0 !== null
  Math.floor(undefined) --> NaN,  NaN !== undefined

These cases might be a slow path, but only when the program is going to throw an
exception.
`x is int` sometimes generates an additional `typeof x === "number"` to avoid
this potential slowness.