[Interpreter] Adds a placeholder merge node when visiting jumps.

[Interpreter] Adds a placeholder merge node when visiting jumps.

This is to fix a bug in the bytecode graph builder. This cl adds a new merge
node before we copy the environment on conditional/unconditional jumps. Since
these environments could be merged later, we add a place holder merge so that
the control dependencies are correctly merged. If we do not have a merge node
we may incorrectly merge the dependencies into the previous block.
For ex: test-run-variables/ContextStoreVariables in cctests.

BUG=v8:4280
LOG=N

Committed: https://crrev.com/d0e01b0ba0f58fb1d94b21e8dcb33bb95917b1f0
Cr-Commit-Position: refs/heads/master@{#33591}

[mythria, 2016-01-28 11:35:12]

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

[commit-bot: I haz the power, 2016-01-28 11:35:17]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1641143002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1641143002/1

[commit-bot: I haz the power, 2016-01-28 11:35:18]

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

[commit-bot: I haz the power, 2016-01-28 11:35:18]

Dry run: No L-G-T-M from a valid reviewer yet. Only full committers are
accepted.
Even if an L-G-T-M may have been provided, it was from a non-committer,
_not_ a full super star committer.
Committers are members of the group "project-v8-committers".
Note that this has nothing to do with OWNERS files.

[mythria, 2016-01-28 11:36:54]

mythria@chromium.org changed reviewers:
+ mstarzinger@chromium.org, oth@chromium.org

[mythria, 2016-01-28 11:36:55]

PTAL

Thanks,
Mythri

[oth, 2016-01-28 11:40:17]

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

[commit-bot: I haz the power, 2016-01-28 11:40:18]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1641143002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1641143002/1

[oth, 2016-01-28 12:01:14]

lgtm, thank you. Nice tests.

[commit-bot: I haz the power, 2016-01-28 12:01:43]

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

[commit-bot: I haz the power, 2016-01-28 12:01:43]

Dry run: This issue passed the CQ dry run.

[Michael Starzinger, 2016-01-28 12:27:50]

LGTM. I am fine with landing this as it is. And especially the tests are
awesome. I might refactor this slightly in the coming days.

https://codereview.chromium.org/1641143002/diff/1/src/compiler/bytecode-graph...
File src/compiler/bytecode-graph-builder.cc (right):

https://codereview.chromium.org/1641143002/diff/1/src/compiler/bytecode-graph...
src/compiler/bytecode-graph-builder.cc:1904: NewMerge();
This can be made nice when we forward propagate environments along the direction
of the data-flow. Can you leave TODO(mstarzinger) here in that regard?

[mythria, 2016-01-28 13:03:16]

Thanks for your reviews.

https://codereview.chromium.org/1641143002/diff/1/src/compiler/bytecode-graph...
File src/compiler/bytecode-graph-builder.cc (right):

https://codereview.chromium.org/1641143002/diff/1/src/compiler/bytecode-graph...
src/compiler/bytecode-graph-builder.cc:1904: NewMerge();
On 2016/01/28 12:27:50, Michael Starzinger wrote:
> This can be made nice when we forward propagate environments along the
direction
> of the data-flow. Can you leave TODO(mstarzinger) here in that regard?

Done.

[mythria, 2016-01-28 13:03:50]

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

[commit-bot: I haz the power, 2016-01-28 13:04:03]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1641143002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1641143002/20001

[commit-bot: I haz the power, 2016-01-28 13:25:54]

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

[commit-bot: I haz the power, 2016-01-28 13:25:55]

Dry run: This issue passed the CQ dry run.

[mythria, 2016-01-28 16:19:43]

The CQ bit was checked by mythria@chromium.org

[mythria, 2016-01-28 16:19:43]

The patchset sent to the CQ was uploaded after l-g-t-m from oth@chromium.org,
mstarzinger@chromium.org
Link to the patchset: https://codereview.chromium.org/1641143002/#ps20001
(title: "Address review comments")

[commit-bot: I haz the power, 2016-01-28 16:19:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1641143002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1641143002/20001

[commit-bot: I haz the power, 2016-01-28 16:21:30]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-01-28 16:22:06]

Description was changed from

==========
[Interpreter] Adds a placeholder merge node when visiting jumps.

This is to fix a bug in the bytecode graph builder. This cl adds a new merge
node before we copy the environment on conditional/unconditional jumps. Since
these environments could be merged later, we add a place holder merge so that
the control dependencies are correctly merged. If we do not have a merge node
we may incorrectly merge the dependencies into the previous block.
For ex: test-run-variables/ContextStoreVariables in cctests.

BUG=v8:4280
LOG=N
==========

to

==========
[Interpreter] Adds a placeholder merge node when visiting jumps.

This is to fix a bug in the bytecode graph builder. This cl adds a new merge
node before we copy the environment on conditional/unconditional jumps. Since
these environments could be merged later, we add a place holder merge so that
the control dependencies are correctly merged. If we do not have a merge node
we may incorrectly merge the dependencies into the previous block.
For ex: test-run-variables/ContextStoreVariables in cctests.

BUG=v8:4280
LOG=N

Committed: https://crrev.com/d0e01b0ba0f58fb1d94b21e8dcb33bb95917b1f0
Cr-Commit-Position: refs/heads/master@{#33591}
==========

[commit-bot: I haz the power, 2016-01-28 16:22:07]

Patchset 2 (id:??) landed as
https://crrev.com/d0e01b0ba0f58fb1d94b21e8dcb33bb95917b1f0
Cr-Commit-Position: refs/heads/master@{#33591}