dart2js cps: Always use interceptors and type tags for 'is' checks.

dart2js cps: Always use interceptors and type tags for 'is' checks.

"x is Foo" will become getInterceptor(x).$isFoo

Testing against a type with type arguments is still a giveup().

This test always works, but is not very fast. For instance, testing
against an int should be "typeof x === 'number' && Math.floor(x) === x".

Following an offline discussion with Karl, the plan is to rewrite
'is'-checks to more fine-grained tests in a CPS optimization pass,
probably the type propagator.

Concretely, we plan to introduce IR nodes like TypeOfTest, FloorTest,
InstanceofTest, etc, which optimization phases can introduce under the
right circumstances. That way, the code generation phase remains simple.

BUG=
R=karlklose@google.com

Committed: https://github.com/dart-lang/sdk/commit/f42a0ef25cd042f7fdd2b6afdc3cbb2a36b6dfd4

[asgerf, 2015-05-21 12:34:07]

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

[karlklose, 2015-05-22 07:40:49]

LGTM.

https://codereview.chromium.org/1144163004/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js_backend/codegen/unsugar.dart (right):

https://codereview.chromium.org/1144163004/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_backend/codegen/unsugar.dart:265:
processTypeOperator(TypeOperator node) {
I think we should do this in the IR builder. Long term we should merge all of
the unsugar rewrites into the IR builder.

[asgerf, 2015-05-22 12:31:36]

PTAL at delta 4 -> 2.

It gets more complicated when we do interception in the builder, but I think
it's something we have to address anyway.

https://codereview.chromium.org/1144163004/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js_backend/codegen/unsugar.dart (right):

https://codereview.chromium.org/1144163004/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_backend/codegen/unsugar.dart:265:
processTypeOperator(TypeOperator node) {
On 2015/05/22 07:40:49, karlklose wrote:
> I think we should do this in the IR builder. Long term we should merge all of
> the unsugar rewrites into the IR builder.

I completely agree. There is a strange limbo in the time between building and
unsugaring where the IR doesn't seem to have clear semantics.

[asgerf, 2015-05-26 15:50:53]

Committed patchset #5 (id:80001) manually as
f42a0ef25cd042f7fdd2b6afdc3cbb2a36b6dfd4 (presubmit successful).