834826 - Eliminate various unnecessary stack roots

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Brian Hackett [Laid off!]]

Attachment: patch

The attached patch fixes various unnecessary roots in SS, reducing the number of constructed roots from 39% of the original total to 22%.  A fair amount of this is removing inference and compilation roots that with bug 772820 are now unnecessary, though there are various miscellaneous rooting refactorings as well.

Comment 1

[Terrence Cole [:terrence]]

How big is the performance regression on SS now?

Comment 2

[Brian Hackett [Laid off!]]

I haven't measured, but will do so after this lands.  My target was to eliminate at least 80% of the roots so this is right about there.  There is still some more that can be done fwiw.

Comment 3

[Terrence Cole [:terrence]]

Comment on attachment 706525 [details] [diff] [review]
patch

Review of attachment 706525 [details] [diff] [review]:
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::: js/src/jsobj.h
@@ +1134,2 @@
>  extern JSBool
> +HasOwnProperty(JSContext *cx, LookupGenericOp lookup,

Disregard my IRC request for a comment here. It did not occur to me that Has*Own*Property would need to throw exceptions.

Comment 4

[Brian Hackett [Laid off!]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/052d2de29f8f

Comment 5

[Brian Hackett [Laid off!]]

(In reply to Terrence Cole [:terrence] from comment #1)
> How big is the performance regression on SS now?

Testing on linux/x64 I get a difference of <1ms on SS, or .4%

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/052d2de29f8f