893897 - Change deoptimization in MonitorAssign to only take effect once we have enough properties

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Boris Zbarsky [:bzbarsky]]

We're trying to guard against hashtable-like things, but since we deoptimize other things that have the same proto (at least for DOM objects) it's better if we're not too eager about it.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Attachment: Don't deoptimize typeobjects in TypeScript::MonitorAssign if they only have a few properties.

Comment 2

[Brian Hackett [Laid off!]]

Comment on attachment 775752 [details] [diff] [review]
Don't deoptimize typeobjects in TypeScript::MonitorAssign if they only have a few properties.

Review of attachment 775752 [details] [diff] [review]:
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::: js/src/jsinferinlines.h
@@ +966,5 @@
>          uint32_t i;
>          if (js_IdIsIndex(id, &i))
>              return;
> +        // But if we don't have too many properties yet, don't do anything.  8
> +        // is a fairly random "not too many" value picked for no good reason.

Newline above this comment.  Maybe remove the second sentence, 8 was picked so that the deoptimization is more likely to kick in only after object initialization.

Comment 3

[Boris Zbarsky [:bzbarsky]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/fc6ed6c80500

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/fc6ed6c80500