[compiler] Make feedback vector cope with flag changes.

[compiler] Make feedback vector cope with flag changes.

This fixes corner cases where the layout of feedback vectors baked into
the snapshot is different from the expected layout, depending on some
runtime flags. We make sure the feedback vector is regenereated for
functions that are not compiled. Flag changes of this kind are only
allowed when code is not serialized.

An alternative solution would be to not serialize the feedback vector
for such cases in the first place. That solution however would have a
higher overhead, as it would required the serializer to be able to
recognize feedback vectors while generating a snapshot.

R=mvstanton@chromium.org
TEST=mjsunit/regress/regress-crbug-600995
BUG=chromium:600995
LOG=n

Committed: https://crrev.com/460bff5fb6af2bd79e610f89afdf6da9dba3cf0c
Cr-Commit-Position: refs/heads/master@{#35339}

[mvstanton, 2016-04-07 14:42:25]

lgtm

[Michael Starzinger, 2016-04-07 15:31:48]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2016-04-07 15:31:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1869693003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1869693003/1

[commit-bot: I haz the power, 2016-04-07 15:34:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-07 15:35:08]

Description was changed from

==========
[compiler] Make feedback vector cope with flag changes.

This fixes corner cases where the layout of feedback vectors baked into
the snapshot is different from the expected layout, depending on some
runtime flags. We make sure the feedback vector is regenereated for
functions that are not compiled. Flag changes of this kind are only
allowed when code is not serialized.

An alternative solution would be to not serialize the feedback vector
for such cases in the first place. That solution however would have a
higher overhead, as it would required the serializer to be able to
recognize feedback vectors while generating a snapshot.

R=mvstanton@chromium.org
TEST=mjsunit/regress/regress-crbug-600995
BUG=chromium:600995
LOG=n
==========

to

==========
[compiler] Make feedback vector cope with flag changes.

This fixes corner cases where the layout of feedback vectors baked into
the snapshot is different from the expected layout, depending on some
runtime flags. We make sure the feedback vector is regenereated for
functions that are not compiled. Flag changes of this kind are only
allowed when code is not serialized.

An alternative solution would be to not serialize the feedback vector
for such cases in the first place. That solution however would have a
higher overhead, as it would required the serializer to be able to
recognize feedback vectors while generating a snapshot.

R=mvstanton@chromium.org
TEST=mjsunit/regress/regress-crbug-600995
BUG=chromium:600995
LOG=n

Committed: https://crrev.com/460bff5fb6af2bd79e610f89afdf6da9dba3cf0c
Cr-Commit-Position: refs/heads/master@{#35339}
==========

[commit-bot: I haz the power, 2016-04-07 15:35:08]

Patchset 1 (id:??) landed as
https://crrev.com/460bff5fb6af2bd79e610f89afdf6da9dba3cf0c
Cr-Commit-Position: refs/heads/master@{#35339}

[Michael Hablich, 2016-04-11 15:09:32]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1876103002/ by hablich@chromium.org.

The reason for reverting is: Blocks current roll:
https://codereview.chromium.org/1876713002/ according to bisect:
https://codereview.chromium.org/1872353002/#ps80001.