Allow LetCont to bind multiple continuations.

Allow LetCont to bind multiple continuations.

LetCont can now bind multiple continuations in the same scope.  As an
example, the 'then' and 'else' continuations of a branch are siblings
in the expression, and neither is in the scope of the other.  None of
the LetCont-bound continuations are in scope for any of the
continuation bodies.  Recursive continuations are still recursive
values, not recursive bindings, so there is no direct way to have
mutually recursive continuations.  This matches the JavaScript
semantics.

R=asgerf@google.com, sigurdm@google.com, karlklose@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=42945

[asgerf, 2015-01-15 15:29:45]

LGTM.

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
File pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart (right):

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart:400: add(new
ir.LetCont(<ir.Continuation>[k], expression));
It may be nicer to introduce a named constructor for the case of multiple
continuations, and preserve the unnamed LetCont constructor for the common case
where there is only one continuation.

E.g.
new ir.LetCont(k, expression)
new ir.LetCont.many([trueCont, falseCont], expression)

Alternatively, the single-continuation constructor could also be named. It would
still be more readable than the pervasive <ir.Continuation>.

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart:538: //   let cont else() =
[[elsePart]]; join(v, ...) in
'let cont else()' --> 'and cont else()' ?

[sigurdm, 2015-01-16 08:01:57]

lgtm

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
File pkg/compiler/lib/src/cps_ir/optimizers.dart (right):

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
pkg/compiler/lib/src/cps_ir/optimizers.dart:54: }
Did anything change here?

[Kevin Millikin (Google), 2015-01-16 08:46:54]

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
File pkg/compiler/lib/src/cps_ir/optimizers.dart (right):

https://codereview.chromium.org/848363002/diff/1/pkg/compiler/lib/src/cps_ir/...
pkg/compiler/lib/src/cps_ir/optimizers.dart:54: }
On 2015/01/16 08:01:57, sigurdm wrote:
> Did anything change here?

My editor inserted a newline at the end of the file.  The style guide seems to
be silent on the issue so I think it's OK.

[Kevin Millikin (Google), 2015-01-16 08:55:34]

Committed patchset #1 (id:1) manually as 42945 (presubmit successful).

[asgerf, 2015-01-16 09:58:42]

On 2015/01/16 08:55:34, kmillikin wrote:
> Committed patchset #1 (id:1) manually as 42945 (presubmit successful).

Seems the commit broke one of the tests:
python tools/test.py --checked -mrelease -t60
dart2js/js_backend_cps_ir_operators_test

The assertion in the _ReductionTask constructor seems to be out of date:

  _ReductionTask(this.kind, this.node) {
    // If new node types are added, they must be marked as deleted in
    // [[_RemovalRedexVisitor]].
    assert(node is LetCont || node is LetPrim);
  }

The node is now a Continuation instead of a LetCont.