[turbofan] First step towards sanitizing for-in and making it optimizable.

[turbofan] First step towards sanitizing for-in and making it optimizable.

In a nutshell: The FILTER_KEY builtin is gone, and was replaced by a
simple runtime call to ForInFilter, which does everything and is even
cheaper (because FILTER_KEY used to call into the runtime anyway).
And ForInFilter returns either the name or undefined, which makes it
possible to remove the control flow construction from the AstGraphBuilder,
and thereby make both the initialization and the per-loop code of for-in
optimizable later (in typed lowering).

R=jarin@chromium.org

Committed: https://crrev.com/e2e47f30be06e6ea6b8a3cc90138381914ecd07d
Cr-Commit-Position: refs/heads/master@{#28711}

[Benedikt Meurer, 2015-05-29 11:55:26]

bmeurer@chromium.org changed reviewers:
+ mstarzinger@chromium.org, plind44@gmail.com

[Benedikt Meurer, 2015-05-29 11:55:26]

Michi, Jaro: Please take a look and comment on the direction.
Paul: Please add MIPS ports.

[paul.l..., 2015-06-01 05:45:29]

paul.lind@imgtec.com changed reviewers:
+ paul.lind@imgtec.com

[paul.l..., 2015-06-01 05:45:30]

I'm OOO today, but have cc'd the mips team. You should have it later this
morning.

[Benedikt Meurer, 2015-06-01 06:10:39]

On 2015/06/01 05:45:30, paul.l... wrote:
> I'm OOO today, but have cc'd the mips team. You should have it later this
> morning.

Thanks Paul. I did the ports myself, because it was only two lines. :-)

[Benedikt Meurer, 2015-06-01 06:16:35]

Hey Jaro,

This is the unoptimized, optimizable, and fixed version of for-in. The next step
is to actually optimize it in typed lowering.
Please take a look.

Thanks,
Benedikt

[Jarin, 2015-06-01 07:16:49]

lgtm

[Benedikt Meurer, 2015-06-01 07:19:09]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-06-01 07:19:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1160983004/40001

[commit-bot: I haz the power, 2015-06-01 07:20:55]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-06-01 07:21:11]

Patchset 3 (id:??) landed as
https://crrev.com/e2e47f30be06e6ea6b8a3cc90138381914ecd07d
Cr-Commit-Position: refs/heads/master@{#28711}