1926226 - Try to lazily allocate slots for attributes marked as FrozenArray

Status: RESOLVED FIXED

(Core :: DOM: Bindings (WebIDL), task, P1)

Description

[Hsin-Yi Tsai (she/her) [:hsinyi]]

spin off from bug 1920082 comment 25 -

Each attribute marked with [FrozenArray] requires a reserved slot on the JS object. We went from 1 to 8 slots, so I think that means the size of the JSObject went from a size of 4 64-bit values to 10 (JSObject_slots2 to JSObject_slots8). I'll try to make this more lazily allocated, but it's annoying because it means more special cases in the generated code.

Comment 1

[Peter Van der Beken [:peterv]]

Attachment: Bug 1926226 - Add a JSSLOT_EXPANDO_COUNT alias in a DOM header, to avoid pulling in XPConnect headers everywhere. r?edgar!

Comment 2

[Peter Van der Beken [:peterv]]

Attachment: Bug 1926226 - Change DEFINE_XRAY_EXPANDO_CLASS to allow passing in custom ops. r?edgar!

Comment 3

[Peter Van der Beken [:peterv]]

Attachment: Bug 1926226 - Add a ClearXrayExpandoSlots helper for WebIDL bindings. r?edgar!

Comment 4

[Peter Van der Beken [:peterv]]

Attachment: Bug 1926226 - Use only one reserved slot for reflected attributes returning a FrozenArray. r?edgar!

HTML reflected IDL attributes that return a FrozenArray<T>? need to cache the
FrozenArray. This switches them from using a reserved slot on the JS object
per attribute to using an array of values for all of these types of attributes
for a particular interface, which is then stored in one reserved slot on the JS
object. This reduces the memory reserved for these attributes if they're not
actually used.

Comment 5

[Peter Van der Beken [:peterv]]

Attachment: Diff of the generated binding code for D228797

Comment 6

[Peter Van der Beken [:peterv]]

Attachment: Diff of the generated binding code for D228797

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/129aa517bd23
Add a JSSLOT_EXPANDO_COUNT alias in a DOM header, to avoid pulling in XPConnect headers everywhere. r=edgar
https://hg.mozilla.org/integration/autoland/rev/028c77b002e3
Change DEFINE_XRAY_EXPANDO_CLASS to allow passing in custom ops. r=edgar
https://hg.mozilla.org/integration/autoland/rev/88a6b0fd4e68
Add a ClearXrayExpandoSlots helper for WebIDL bindings. r=edgar
https://hg.mozilla.org/integration/autoland/rev/5560b5784075
Use only one reserved slot for reflected attributes returning a FrozenArray. r=edgar

Comment 8

[pstanciu]

https://hg.mozilla.org/mozilla-central/rev/129aa517bd23
https://hg.mozilla.org/mozilla-central/rev/028c77b002e3
https://hg.mozilla.org/mozilla-central/rev/88a6b0fd4e68
https://hg.mozilla.org/mozilla-central/rev/5560b5784075