dart2js cps: Better 'is int' checks.

dart2js cps: Better 'is int' checks.

BUG=
R=karlklose@google.com

Committed: https://github.com/dart-lang/sdk/commit/14749489efdef1a0ce81048310c590ce6717f6fa

[asgerf, 2015-06-17 17:14:38]

asgerf@google.com changed reviewers:
+ karlklose@google.com

[karlklose, 2015-06-18 07:36:56]

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
File pkg/compiler/lib/src/cps_ir/builtin_operator.dart (right):

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
pkg/compiler/lib/src/cps_ir/builtin_operator.dart:21: /// Some operators,
notably [IsFloor] and [IsNumberAndFloor], take "repeated"
We could avoid this problem by adding 'typeof' and 'Math.isFloor' as builtin
operators instead.  WDYT?

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
File pkg/compiler/lib/src/cps_ir/type_propagation.dart (right):

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
pkg/compiler/lib/src/cps_ir/type_propagation.dart:234: /// In other words, if
true is returned, and IF the value is a number, then
Remove 'IF'.

[asgerf, 2015-06-18 09:08:49]

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
File pkg/compiler/lib/src/cps_ir/builtin_operator.dart (right):

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
pkg/compiler/lib/src/cps_ir/builtin_operator.dart:21: /// Some operators,
notably [IsFloor] and [IsNumberAndFloor], take "repeated"
On 2015/06/18 07:36:56, karlklose wrote:
> We could avoid this problem by adding 'typeof' and 'Math.isFloor' as builtin
> operators instead.  WDYT?

(Summary from offline discussion with Karl)

I agree that it's somewhat unusual, but I wouldn't go as far as calling it a
problem, because there really is no harm in it. It has the positive benefit of
bringing awareness to an issue that is otherwise easily overlooked.

Try to see codegen_helpers.dart:410 to see the corresponding logic in SSA. The
"complexity" was there all along, we are just tackling it head on instead of
leaving it as a subtlety for assignment propagation to think about.

But is true, with more fine-grained operators, it would go away entirely. But
there are some drawbacks to fine-grained operators:
1. They require more IR nodes at runtime.
2. Building complex expressions is more complicated than just adding one
operator.
3. Analyzing the resulting IR is harder. The IR for IsNumberAndFloor would
require two LetConts and a Branch, and then it's much harder to see that it just
checks if a value is an integer.

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
File pkg/compiler/lib/src/cps_ir/type_propagation.dart (right):

https://codereview.chromium.org/1184963006/diff/1/pkg/compiler/lib/src/cps_ir...
pkg/compiler/lib/src/cps_ir/type_propagation.dart:234: /// In other words, if
true is returned, and IF the value is a number, then
On 2015/06/18 07:36:56, karlklose wrote:
> Remove 'IF'.

Done.

[karlklose, 2015-06-18 09:13:49]

LGTM.

[asgerf, 2015-06-18 09:25:03]

Committed patchset #2 (id:20001) manually as
14749489efdef1a0ce81048310c590ce6717f6fa (presubmit successful).