dart2js: fill in the basic functionality of the startup emitter.

dart2js: fill in the basic functionality of the startup emitter.

R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/dcb76e65e6d12ce6fd0c1c3bf302d8f61ae74f8f

[floitsch, 2015-07-10 17:21:44]

floitsch@google.com changed reviewers:
+ herhut@google.com

[Siggi Cherem (dart-lang), 2015-07-14 16:17:02]

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

[Siggi Cherem (dart-lang), 2015-07-14 16:17:03]

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
(right):

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:9: const
String deferredInitializersGlobal = r"$__dart_deferred_initializers__";
could you also delete the duplicate declarations of these two constants in
ModelEmitter?

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:520: case
1: return "function() { return this[#]; }";
could we define constants to make it easier to understand what these flags mean?

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:647: //
constant-holder variable).
would it be worth defining an object literal for each layer of constants in the
dependency-tree?

For example:

const a = const [1];
const b = const [2];
const c = const [a];
const d = const [c, b];


C1 = {  // leaf constants
  a: [1],
  b: [2],
};
C2 = {  // depend on C1 constants
  c: [C1.a],
}
C3 = {  // depend on C2 or C1 constants
  d: [C2.c, C1.b],
}

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:668:
[field.holder.name, field.name, field.code]);
what is field.code when you don't require an initializer? would this practically
be 'null'? (if so, maybe switch to just write it that way?)

[floitsch, 2015-07-22 15:02:13]

PTAL.

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
(right):

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:9: const
String deferredInitializersGlobal = r"$__dart_deferred_initializers__";
On 2015/07/14 16:17:02, Siggi Cherem (dart-lang) wrote:
> could you also delete the duplicate declarations of these two constants in
> ModelEmitter?

These constants should be in the ModelEmitter. Removed them here.

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:520: case
1: return "function() { return this[#]; }";
On 2015/07/14 16:17:02, Siggi Cherem (dart-lang) wrote:
> could we define constants to make it easier to understand what these flags
mean?

I just added more getters on the Field class. If you prefer constants I can
change it, but this seems to be simpler.

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:647: //
constant-holder variable).
On 2015/07/14 16:17:02, Siggi Cherem (dart-lang) wrote:
> would it be worth defining an object literal for each layer of constants in
the
> dependency-tree?
> 
> For example:
> 
> const a = const [1];
> const b = const [2];
> const c = const [a];
> const d = const [c, b];
> 
> 
> C1 = {  // leaf constants
>   a: [1],
>   b: [2],
> };
> C2 = {  // depend on C1 constants
>   c: [C1.a],
> }
> C3 = {  // depend on C2 or C1 constants
>   d: [C2.c, C1.b],
> }

Yes, but for that we would need to have the constant-hierarchy.
Also, we currently emit all nested constants as top-level constants, even if
they are only used to initialize other constants.

This is something that needs some work in the constant-handler, so I'm not
changing it here.

https://codereview.chromium.org/1234493003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart:668:
[field.holder.name, field.name, field.code]);
On 2015/07/14 16:17:02, Siggi Cherem (dart-lang) wrote:
> what is field.code when you don't require an initializer? would this
practically
> be 'null'? (if so, maybe switch to just write it that way?)

It is the js-code 'null'. So the code itself is not null, but the js-expression
it contains evaluates to `null`.

I could check if field.code is js.LiteralNull, but I don't see the advantage.
(That said, it might save space, to initialize statics that have the same value
in one go: a.x = a.y = ... = 0;)

I added a TODO.

[Siggi Cherem (dart-lang), 2015-07-22 20:55:09]

lgtm

[floitsch, 2015-07-29 17:17:37]

Committed patchset #4 (id:60001) manually as
dcb76e65e6d12ce6fd0c1c3bf302d8f61ae74f8f (presubmit successful).