[contexts] Place the initial JSArray maps on the native context directly.

[contexts] Place the initial JSArray maps on the native context directly.

No need to have an indirection to get to the initial JSArray maps from
the native context; we only cache the fast elements maps anyway, so
those could live on the native context directly. This will also
integrate nicely with the load/store propagation in TurboFan (once we
propagate the immutable flag for FieldAccess as well).

Drive-by-fix: Also don't embed any of the initial JSArray maps in
TurboFan generated code when allocating a new JSArray, but instead
always load the appropriate map from the native context.  This way
we ensure that we never leak a reference to one of those maps and
its as efficient as embedding a constant map.

R=yangguo@chromium.org

Committed: https://crrev.com/5964152c8fb61d1b7e19d6c678367fcf014b7700
Cr-Commit-Position: refs/heads/master@{#32779}

[Benedikt Meurer, 2015-12-11 06:05:10]

Hey Yang,

Some cleanup/refactoring on the way we deal with the initial maps for the Array
constructor.
Please take a look.

Thanks,
Benedikt

[Yang, 2015-12-11 06:15:12]

On 2015/12/11 06:05:10, Benedikt Meurer wrote:
> Hey Yang,
> 
> Some cleanup/refactoring on the way we deal with the initial maps for the
Array
> constructor.
> Please take a look.
> 
> Thanks,
> Benedikt

We do the calculation for the offset in several places. Wouldn't it be better to
introduce a function, something like Context::ArrayMapIndex(ElementsKind
elements_kind, bool is_strong) that calculates it? Even if it's just a trivial
addition.

Otherwise LGTM.

[Benedikt Meurer, 2015-12-11 06:27:53]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-12-11 06:27:54]

The patchset sent to the CQ was uploaded after l-g-t-m from yangguo@chromium.org
Link to the patchset: https://codereview.chromium.org/1516433005/#ps40001
(title: "Address comment.")

[commit-bot: I haz the power, 2015-12-11 06:28:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1516433005/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1516433005/40001

[commit-bot: I haz the power, 2015-12-11 06:50:52]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-12-11 06:51:30]

Description was changed from

==========
[contexts] Place the initial JSArray maps on the native context directly.

No need to have an indirection to get to the initial JSArray maps from
the native context; we only cache the fast elements maps anyway, so
those could live on the native context directly. This will also
integrate nicely with the load/store propagation in TurboFan (once we
propagate the immutable flag for FieldAccess as well).

Drive-by-fix: Also don't embed any of the initial JSArray maps in
TurboFan generated code when allocating a new JSArray, but instead
always load the appropriate map from the native context.  This way
we ensure that we never leak a reference to one of those maps and
its as efficient as embedding a constant map.

R=yangguo@chromium.org
==========

to

==========
[contexts] Place the initial JSArray maps on the native context directly.

No need to have an indirection to get to the initial JSArray maps from
the native context; we only cache the fast elements maps anyway, so
those could live on the native context directly. This will also
integrate nicely with the load/store propagation in TurboFan (once we
propagate the immutable flag for FieldAccess as well).

Drive-by-fix: Also don't embed any of the initial JSArray maps in
TurboFan generated code when allocating a new JSArray, but instead
always load the appropriate map from the native context.  This way
we ensure that we never leak a reference to one of those maps and
its as efficient as embedding a constant map.

R=yangguo@chromium.org

Committed: https://crrev.com/5964152c8fb61d1b7e19d6c678367fcf014b7700
Cr-Commit-Position: refs/heads/master@{#32779}
==========

[commit-bot: I haz the power, 2015-12-11 06:51:31]

Patchset 3 (id:??) landed as
https://crrev.com/5964152c8fb61d1b7e19d6c678367fcf014b7700
Cr-Commit-Position: refs/heads/master@{#32779}