1723085 - Optimize reserved slot accesses

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[Jan de Mooij [:jandem]]

After removing private slots in bug 1719457, we can optimize gets/sets of reserved slots by relying on the fact that fixed slots are used for them (up to the maximum number of fixed slots).

This means we no longer need to read obj->shape->numFixedSlots when getting/setting reserved slots and can optimize a slot access with constant index (the common case) to a single memory load/store.

Unfortunately doing the same for the JS::GetReservedSlot and JS::SetReservedSlot APIs is more complicated because these can also be used for proxies.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1723085 part 1 - Remove getReservedSlotRef. r?jonco!

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1723085 part 2 - Optimize getting/setting reserved slots inside the JS engine. r?jonco!

After removing private slots, we can optimize gets/sets of reserved slots by
relying on the fact that fixed slots are used for them (up to the maximum number
of fixed slots).

This means we no longer need to read obj->shape->numFixedSlots when getting/setting
reserved slots and can optimize a slot access with constant index (the common case)
to a single memory load/store.

Unfortunately doing the same for the JS::GetReservedSlot and JS::SetReservedSlot
APIs is more complicated because these can also be used for proxies and swappable
DOM objects.

Depends on D121355

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1723085 part 3 - Use getReservedSlot/setReservedSlot in more places. r?jonco!

Depends on D121356

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/mozilla-central/rev/54dc60004dcf
part 1 - Remove getReservedSlotRef. r=jonco
https://hg.mozilla.org/mozilla-central/rev/dfd6d7623515
part 2 - Optimize getting/setting reserved slots inside the JS engine. r=jonco
https://hg.mozilla.org/mozilla-central/rev/62aa961c1bd7
part 3 - Use getReservedSlot/setReservedSlot in more places. r=jonco

Comment 5

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/54dc60004dcf
https://hg.mozilla.org/mozilla-central/rev/dfd6d7623515
https://hg.mozilla.org/mozilla-central/rev/62aa961c1bd7