Bug 239545 – Avoid call to convertToASCIILowercase() in SelectorFilter::collectElementIdentifierHashes() in the common case

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Chris Dumez]

Avoid call to convertToASCIILowercase() in SelectorFilter::collectElementIdentifierHashes() in the common case.

[Chris Dumez]

Created attachment 457993 [details]
Patch

[Sam Weinig]

Comment on attachment 457993 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=457993&action=review

> Source/WebCore/css/SelectorFilter.cpp:50
> +    AtomString tagLowercaseLocalName = LIKELY(element.isHTMLElement() && !element.isUnknownElement()) ? element.localName() : element.localName().convertToASCIILowercase();

A comment explaining this assumption would be useful even with the assert.

[EWS]

Committed r293123 (249826@main): <https://commits.webkit.org/249826@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 457993 [details].

[Radar WebKit Bug Importer]

<rdar://problem/92054703>

[Darin Adler]

Comment on attachment 457993 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=457993&action=review

>> Source/WebCore/css/SelectorFilter.cpp:50
>> +    AtomString tagLowercaseLocalName = LIKELY(element.isHTMLElement() && !element.isUnknownElement()) ? element.localName() : element.localName().convertToASCIILowercase();
> 
> A comment explaining this assumption would be useful even with the assert.

The classic way to do this is to write a function named localNameIsKnownToBeLowercase or localNameMayContainUppercaseASCII. Then that function is the perfect place for the comment explaining why the rule is correct, and here the code is more obviously correct.

[Chris Dumez]

(In reply to Darin Adler from comment #5)
> Comment on attachment 457993 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=457993&action=review
> 
> >> Source/WebCore/css/SelectorFilter.cpp:50
> >> +    AtomString tagLowercaseLocalName = LIKELY(element.isHTMLElement() && !element.isUnknownElement()) ? element.localName() : element.localName().convertToASCIILowercase();
> > 
> > A comment explaining this assumption would be useful even with the assert.
> 
> The classic way to do this is to write a function named
> localNameIsKnownToBeLowercase or localNameMayContainUppercaseASCII. Then
> that function is the perfect place for the comment explaining why the rule
> is correct, and here the code is more obviously correct.

Oh, I missed Sam's comment before landing. Sorry about that. I'll follow-up.

[Chris Dumez]

0.38% progression on Speedometer on Intel, neutral on Apple Silicon.

[Chris Dumez]

(In reply to Darin Adler from comment #5)
> Comment on attachment 457993 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=457993&action=review
> 
> >> Source/WebCore/css/SelectorFilter.cpp:50
> >> +    AtomString tagLowercaseLocalName = LIKELY(element.isHTMLElement() && !element.isUnknownElement()) ? element.localName() : element.localName().convertToASCIILowercase();
> > 
> > A comment explaining this assumption would be useful even with the assert.
> 
> The classic way to do this is to write a function named
> localNameIsKnownToBeLowercase or localNameMayContainUppercaseASCII. Then
> that function is the perfect place for the comment explaining why the rule
> is correct, and here the code is more obviously correct.

Done in <https://commits.webkit.org/r293138>.