Add IR nodes needed for deferred loading.

Add IR nodes needed for deferred loading.

BUG=
R=sra@google.com

Committed: https://github.com/dart-lang/sdk/commit/fd6018d2abd3896e44784c4b8de5f888910989a6

[sra1, 2017-01-30 18:21:33]

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

[sra1, 2017-01-30 18:21:33]

I think we should make the check a special instruction.
It has special properties that regular mutable state does not:

1. The state is monotonic (unload->loaded). We can optimize multiple library
checks, something that cannot be done for a non-final static bool without (a)
global analysis (b) more advanced analysis that we currently do.

2. The code to throw the exception, if lowered to a throw instruction, will be
much larger in JS than a special instruction.

3. The LoadLibrary instruction is related to some specific checked state, but
this is not explicit. So the best we can do in analysis is know that some of the
static bools have changed.  We do not currently model changes to a set of
variables in any of our global analyses.

[asgerf, 2017-01-31 11:17:01]

On 2017/01/30 18:21:33, sra1 wrote:
> I think we should make the check a special instruction.
> It has special properties that regular mutable state does not:
> 
> 1. The state is monotonic (unload->loaded). We can optimize multiple library
> checks, something that cannot be done for a non-final static bool without (a)
> global analysis (b) more advanced analysis that we currently do.
> 
> 2. The code to throw the exception, if lowered to a throw instruction, will be
> much larger in JS than a special instruction.
> 
> 3. The LoadLibrary instruction is related to some specific checked state, but
> this is not explicit. So the best we can do in analysis is know that some of
the
> static bools have changed.  We do not currently model changes to a set of
> variables in any of our global analyses.

Good points.

floitch also explained to me some points about how libraries are split into
smaller
fragments, so each deferred import only loads what is loaded through that
particular
import.

I've added explicit deferred imports and an explicit check instruction.  The
frontend
still doesn't do anything new.

I'm still not sure if the frontend should actually insert the checks using Let
or if it
should be embedded in the static-access expression (StaticX and
ConstructorInvocation).
I prefer to insert the checks with a Let, but let me know if there are any
requirements
against that.

[asgerf, 2017-01-31 11:17:27]

Description was changed from

==========
Add a LoadLibrary IR node for deferred loading.

The intent is that the frontend should insert the checks on deferred
import prefixes, while the actual downloading and linking of a given
library is left up to the backend through this node.

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

to

==========
Add a IR nodes needed for deferred loading.

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

[sra1, 2017-02-01 01:11:16]

I think this is OK. We are just going to look at some test cases before giving
an LGTM

https://codereview.chromium.org/2659343002/diff/20001/pkg/kernel/binary.md
File pkg/kernel/binary.md (right):

https://codereview.chromium.org/2659343002/diff/20001/pkg/kernel/binary.md#ne...
pkg/kernel/binary.md:671: 
Do you need at add DeferredLibary and the check here?

[Emily Fortuna, 2017-02-02 00:44:40]

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

[Emily Fortuna, 2017-02-02 00:44:41]

just wanted to pile on, I think this seems reasonable. Thanks for writing it up,
Asger!

[asgerf, 2017-02-02 12:50:36]

Just let me know if you want to me to land this, or, if you prefer, you can take
it over from here.

(Next week I am on vacation)

https://codereview.chromium.org/2659343002/diff/20001/pkg/kernel/binary.md
File pkg/kernel/binary.md (right):

https://codereview.chromium.org/2659343002/diff/20001/pkg/kernel/binary.md#ne...
pkg/kernel/binary.md:671: 
On 2017/02/01 01:11:16, sra1 wrote:
> Do you need at add DeferredLibary and the check here?

Yep. Updated.

[Emily Fortuna, 2017-02-02 18:22:38]

On 2017/02/02 12:50:36, asgerf wrote:
> Just let me know if you want to me to land this, or, if you prefer, you can
take
> it over from here.
> 
> (Next week I am on vacation)
> 
> https://codereview.chromium.org/2659343002/diff/20001/pkg/kernel/binary.md
> File pkg/kernel/binary.md (right):
> 
>
https://codereview.chromium.org/2659343002/diff/20001/pkg/kernel/binary.md#ne...
> pkg/kernel/binary.md:671: 
> On 2017/02/01 01:11:16, sra1 wrote:
> > Do you need at add DeferredLibary and the check here?
> 
> Yep. Updated.

You landing it is fine with me!

[asgerf, 2017-02-03 10:22:39]

Description was changed from

==========
Add a IR nodes needed for deferred loading.

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

to

==========
Add IR nodes needed for deferred loading.

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

[sra1, 2017-02-03 23:43:45]

lgtm

[asgerf, 2017-02-13 13:31:30]

Description was changed from

==========
Add IR nodes needed for deferred loading.

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

to

==========
Add IR nodes needed for deferred loading.

BUG=
R=sra@google.com

Committed:
https://github.com/dart-lang/sdk/commit/fd6018d2abd3896e44784c4b8de5f888910989a6
==========

[asgerf, 2017-02-13 13:31:31]

Committed patchset #3 (id:40001) manually as
fd6018d2abd3896e44784c4b8de5f888910989a6 (presubmit successful).