[turbofan] Fixed reuse of nested ObjectState in escape analysis

[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a referencing VirtualObject, and that each VirtualObjects maintains a cache of an ObjectState node. Together, this leads to inappropriate reuse of ObjectState nodes.
This fix simply always copies all virtual objects when a new VirtualState is created. This is clearly not optimal to avoid clones, but determining precisely which virtual objects are affected by a write is a transitive closure computation on the virtual objects of a virtual state. Alternatively, one could change the semantics of the node cache.

BUG=v8:5611
Committed: https://crrev.com/288d38127a953eb43f0175637ac16d3c371c1422
Cr-Commit-Position: refs/heads/master@{#40854}

[Tobias Tebbi, 2016-11-08 15:31:55]

Description was changed from

==========
[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a
referencing VirtualObject, and that each VirtualObjects maintains a cache of an
ObjectState node. Together, this leads to inappropriate reuse of ObjectState
nodes.
This fix simply always copies all virtual objects when a new VirtualState is
created. This is clearly not optimal to avoid clones, but determining precisely
which virtual objects are affected by a write is a transitive closure
computation on the virtual objects of a virtual state. Alternatively, one could
change the semantics of the node cache.

BUG=v8:5611
==========

to

==========
[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a
referencing VirtualObject, and that each VirtualObjects maintains a cache of an
ObjectState node. Together, this leads to inappropriate reuse of ObjectState
nodes.
This fix simply always copies all virtual objects when a new VirtualState is
created. This is clearly not optimal to avoid clones, but determining precisely
which virtual objects are affected by a write is a transitive closure
computation on the virtual objects of a virtual state. Alternatively, one could
change the semantics of the node cache.

BUG=v8:5611
==========

[Tobias Tebbi, 2016-11-08 15:31:56]

tebbi@chromium.org changed reviewers:
+ bmeurer@chromium.org, mstarzinger@chromium.org

[Benedikt Meurer, 2016-11-08 19:32:02]

Nice. LGTM.

[Tobias Tebbi, 2016-11-09 09:42:41]

The CQ bit was checked by tebbi@chromium.org

[commit-bot: I haz the power, 2016-11-09 09:42:43]

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, 2016-11-09 10:08:47]

Description was changed from

==========
[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a
referencing VirtualObject, and that each VirtualObjects maintains a cache of an
ObjectState node. Together, this leads to inappropriate reuse of ObjectState
nodes.
This fix simply always copies all virtual objects when a new VirtualState is
created. This is clearly not optimal to avoid clones, but determining precisely
which virtual objects are affected by a write is a transitive closure
computation on the virtual objects of a virtual state. Alternatively, one could
change the semantics of the node cache.

BUG=v8:5611
==========

to

==========
[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a
referencing VirtualObject, and that each VirtualObjects maintains a cache of an
ObjectState node. Together, this leads to inappropriate reuse of ObjectState
nodes.
This fix simply always copies all virtual objects when a new VirtualState is
created. This is clearly not optimal to avoid clones, but determining precisely
which virtual objects are affected by a write is a transitive closure
computation on the virtual objects of a virtual state. Alternatively, one could
change the semantics of the node cache.

BUG=v8:5611
==========

[commit-bot: I haz the power, 2016-11-09 10:08:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-17 22:27:10]

Description was changed from

==========
[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a
referencing VirtualObject, and that each VirtualObjects maintains a cache of an
ObjectState node. Together, this leads to inappropriate reuse of ObjectState
nodes.
This fix simply always copies all virtual objects when a new VirtualState is
created. This is clearly not optimal to avoid clones, but determining precisely
which virtual objects are affected by a write is a transitive closure
computation on the virtual objects of a virtual state. Alternatively, one could
change the semantics of the node cache.

BUG=v8:5611
==========

to

==========
[turbofan] Fixed reuse of nested ObjectState in escape analysis

The problem is that writes to nested objects do not lead to a copy of a
referencing VirtualObject, and that each VirtualObjects maintains a cache of an
ObjectState node. Together, this leads to inappropriate reuse of ObjectState
nodes.
This fix simply always copies all virtual objects when a new VirtualState is
created. This is clearly not optimal to avoid clones, but determining precisely
which virtual objects are affected by a write is a transitive closure
computation on the virtual objects of a virtual state. Alternatively, one could
change the semantics of the node cache.

BUG=v8:5611

Committed: https://crrev.com/288d38127a953eb43f0175637ac16d3c371c1422
Cr-Commit-Position: refs/heads/master@{#40854}
==========

[commit-bot: I haz the power, 2016-11-17 22:27:11]

Patchset 1 (id:??) landed as
https://crrev.com/288d38127a953eb43f0175637ac16d3c371c1422
Cr-Commit-Position: refs/heads/master@{#40854}