Bug 144456

Summary:

TypeOfIsUndefined by-type folding should take advantage of the masquerades-as-undefined watchpoint

Product:

WebKit

Reporter:

Filip Pizlo <fpizlo>

Component:

JavaScriptCore

Assignee:

Alexey Shvayka <ashvayka>

Status:

NEW ---

Severity:

Enhancement

CC:

ashvayka, ews-watchlist, keith_miller, mark.lam, msaboff, saam, tzagallo

Priority:

Version:

WebKit Nightly Build

Hardware:

All

OS:

All

Bug Depends on:

144409

Bug Blocks:

Attachments:

Description	Flags
Patch	fpizlo: review+

Description Filip Pizlo 2015-04-30 10:31:02 PDT

This would allow us to fold more things.

Comment 1 Alexey Shvayka 2021-08-04 14:52:44 PDT

Created attachment 434939 [details]
Patch

Comment 2 Alexey Shvayka 2021-08-04 14:53:30 PDT

(In reply to Alexey Shvayka from comment #1)
> Created attachment 434939 [details]
> Patch

                                                    r280626                    patch

is-undefined-fold-tricky-spec-object-other      30.6171+-0.7028     ^     21.8494+-0.6913        ^ definitely 1.4013x faster

Comment 3 Filip Pizlo 2021-08-04 15:10:39 PDT

Comment on attachment 434939 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=434939&action=review

> Source/JavaScriptCore/ChangeLog:12
> +        TypeOfIsObject / TypeOfIsFunction by-type folding can't be improved in the same way:
> +        even if SpecObjectOther is a proven non-masquerader, we don't know if it's callable.

Can you replace the FIXME's with comments to this effect?  This is an easy detail to forget.  I would say something like - we could use the masquerade watchpoint to prove it's not undefined, but we don't have a trick for callability.