881517 - Remove mPrototypeNoHelper

Status: RESOLVED FIXED

(Core :: XPConnect, defect)

Description

[Bobby Holley (:bholley)]

I saw the JS guys trying to root this thing in bug 878160, and am pretty sure we don't need it anymore. Patches coming up.

Comment 1

[Bobby Holley (:bholley)]

https://tbpl.mozilla.org/?tree=Try&rev=07b04bbc012c

Comment 2

[Bobby Holley (:bholley)]

Attachment: Part 1 - Just use Object.prototype for vanilla XPCWNs. v1

Comment 3

[Bobby Holley (:bholley)]

Attachment: Part 2 - Remove mPrototypeNoHelper machinery. v1

The comments surrounding it don't make any sense to me, and most likely applied
to a pre-CPG world.

Comment 4

[Bobby Holley (:bholley)]

This is green

Comment 5

[Bobby Holley (:bholley)]

Brian -

Blake says that this was probably an old performance optimization (back when Shapes were called scopes) that's trying to share a Shape for all XPCWrappedNatives that don't have a custom proto. Does this make sense in the modern world, or can we kill it and just use Object.prototype?

Comment 6

[Blake Kaplan (:mrbkap) (inactive)]

Comment on attachment 760623 [details] [diff] [review]
Part 2 - Remove mPrototypeNoHelper machinery. v1

I've convinced myself this is correct. The old code that decided whether or not to share the base shape with the proto did require the proto to have the same number of fixed slots as the new object and the new code no longer does.

bhackett should still chime in, though.

Comment 7

[Brian Hackett [Laid off!]]

Yeah, these days objects will share an initial shape if their prototype and other attributes are the same, regardless of what that prototype is.

Comment 8

[Bobby Holley (:bholley)]

remote:   https://hg.mozilla.org/integration/mozilla-inbound/rev/9a2f3ec731e4
remote:   https://hg.mozilla.org/integration/mozilla-inbound/rev/a28d5406031e

Comment 9

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/9a2f3ec731e4
https://hg.mozilla.org/mozilla-central/rev/a28d5406031e