[interpreter] Don't assume generator functions do an initial yield.

[interpreter] Don't assume generator functions do an initial yield.

Async functions are implemented via special generator functions; special in the
sense that they generally do not immediately yield.  However, our generators
implementation still assumed that every generator function initially yields
(concretely: before doing the state dispatch in a loop header).  This CL fixes
that.

R=littledan@chromium.org, rmcilroy@chromium.org
BUG=chromium:638019
Committed: https://crrev.com/7fe4d930c9772dfc5f8e506920ad435863ee3b1d
Cr-Commit-Position: refs/heads/master@{#38684}

[neis, 2016-08-17 11:38:56]

The CQ bit was checked by neis@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-17 11:39:01]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-17 12:30:15]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-17 12:30:16]

Dry run: This issue passed the CQ dry run.

[Dan Ehrenberg, 2016-08-17 13:44:34]

lgtm

https://codereview.chromium.org/2253033002/diff/1/src/interpreter/bytecode-ge...
File src/interpreter/bytecode-generator.cc (right):

https://codereview.chromium.org/2253033002/diff/1/src/interpreter/bytecode-ge...
src/interpreter/bytecode-generator.cc:882:
.StoreAccumulatorInRegister(generator_state_);
Looks like you're doing this extra load/store for generators too, not just async
functions, is this right? Seems fine but very slightly suboptimal.

[rmcilroy, 2016-08-17 13:53:40]

LGTM.

https://codereview.chromium.org/2253033002/diff/1/src/interpreter/bytecode-ge...
File src/interpreter/bytecode-generator.cc (right):

https://codereview.chromium.org/2253033002/diff/1/src/interpreter/bytecode-ge...
src/interpreter/bytecode-generator.cc:882:
.StoreAccumulatorInRegister(generator_state_);
On 2016/08/17 13:44:34, Dan Ehrenberg wrote:
> Looks like you're doing this extra load/store for generators too, not just
async
> functions, is this right? Seems fine but very slightly suboptimal.

+1

[neis, 2016-08-17 15:01:01]

On 2016/08/17 13:53:40, rmcilroy wrote:
> LGTM.
> 
>
https://codereview.chromium.org/2253033002/diff/1/src/interpreter/bytecode-ge...
> File src/interpreter/bytecode-generator.cc (right):
> 
>
https://codereview.chromium.org/2253033002/diff/1/src/interpreter/bytecode-ge...
> src/interpreter/bytecode-generator.cc:882:
> .StoreAccumulatorInRegister(generator_state_);
> On 2016/08/17 13:44:34, Dan Ehrenberg wrote:
> > Looks like you're doing this extra load/store for generators too, not just
> async
> > functions, is this right? Seems fine but very slightly suboptimal.
> 
> +1

That's true. But it's done only once per generator instantiation (not per
resume) and I think it's a good idea to keep the code independent of the
particular kind of resumable.

[neis, 2016-08-17 15:01:21]

The CQ bit was checked by neis@chromium.org

[commit-bot: I haz the power, 2016-08-17 15:01:30]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-17 15:03:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-17 15:03:50]

Description was changed from

==========
[interpreter] Don't assume generator functions do an initial yield.

Async functions are implemented via special generator functions; special in the
sense that they generally do not immediately yield.  However, our generators
implementation still assumed that every generator function initially yields
(concretely: before doing the state dispatch in a loop header).  This CL fixes
that.

R=littledan@chromium.org, rmcilroy@chromium.org
BUG=chromium:638019
==========

to

==========
[interpreter] Don't assume generator functions do an initial yield.

Async functions are implemented via special generator functions; special in the
sense that they generally do not immediately yield.  However, our generators
implementation still assumed that every generator function initially yields
(concretely: before doing the state dispatch in a loop header).  This CL fixes
that.

R=littledan@chromium.org, rmcilroy@chromium.org
BUG=chromium:638019

Committed: https://crrev.com/7fe4d930c9772dfc5f8e506920ad435863ee3b1d
Cr-Commit-Position: refs/heads/master@{#38684}
==========

[commit-bot: I haz the power, 2016-08-17 15:03:51]

Patchset 1 (id:??) landed as
https://crrev.com/7fe4d930c9772dfc5f8e506920ad435863ee3b1d
Cr-Commit-Position: refs/heads/master@{#38684}