1839082 - Some more improvements for attribute selector matching

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, task)

Description

[Markus Stange [:mstange]]

To speed up the testcase in bug 1837673 (attachment 9338349 [details]).

Comment 1

[Markus Stange [:mstange]]

Attachment: Bug 1839082 - Optimize attribute traversal in stylo. r=emilio

This deduplicates some checks for whether attr() is None,
and avoids a flag check in the chain iterator.

On my machine, with a local macOS arm64 --enable-release non-PGO build,
this fix reduces the time spent in has_attr by 38% on the testcase
in bug 1837673.

Comment 2

[Markus Stange [:mstange]]

Attachment: Bug 1839082 - Add a fast path to nsAttrValue::Equals for comparing a string attribute to an atom value. r=emilio

This improves the testcase in bug 1837673 by a small amount.

In this profile you can see nsAttrValue::GetStoredAtom() call BaseType(),
and then nsAttrValue::Equals(string) calls it again: https://share.firefox.dev/3p8r71q

Depends on D181346

Comment 3

[Markus Stange [:mstange]]

Attachment: Bug 1839082 - Move attribute checking around so that the attribute name can be checked without a function call. r=emilio

The goal here is to inline the loop and attribute name check into the caller.
Once an attribute with a matching name is found, we do the remainder of the
checks (namespace, attribute value) with a function call.

This probably helps some cases and hurts others.

Depends on D181347

Comment 4

[Markus Stange [:mstange]]

Attachment: Bug 1839082 - Add a fast path for non-compound attribute selectors. r=emilio

This improves the testcase in bug 1837673, because it means that we only
check attributes once. Before this patch, we would check them twice: First,
the SimpleFilter path would check for the presence of the attribute, and then
later we would enumerate attributes again to check the attribute value.
Now we don't use the SimpleFilter path anymore and go straight to attribute
enumeration.

TODO: One of the checks that this skips is a quirks mode check - what are the effects of it? Do we need to handle something about it here?

Depends on D181348

Comment 5

[Markus Stange [:mstange]]

Attachment: Bug 1839082 - Remove iter_attrs. This is no longer needed, now that attributes are always a single slice. r=emilio

Depends on D181347

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/50016a097d86
Add a fast path to nsAttrValue::Equals for comparing a string attribute to an atom value. r=emilio
https://hg.mozilla.org/integration/autoland/rev/ab90251925ec
Remove iter_attrs. This is no longer needed, now that attributes are always a single slice. r=emilio
https://hg.mozilla.org/integration/autoland/rev/5b02f6714bb7
Move attribute checking around so that the attribute name can be checked without a function call. r=emilio
https://hg.mozilla.org/integration/autoland/rev/50d6377ff840
Add a fast path for non-compound attribute selectors. r=emilio

Comment 7

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/50016a097d86
https://hg.mozilla.org/mozilla-central/rev/ab90251925ec
https://hg.mozilla.org/mozilla-central/rev/5b02f6714bb7
https://hg.mozilla.org/mozilla-central/rev/50d6377ff840