This gmail profile has a sample showing IsCJKFont. Spoke to jfkthame and he thinks it could be optimized. Profile: https://perf-html.io/public/760909d9456fb753500182eb04f593317b948d48/calltree/?invertCallstack&search=isCJKFont&thread=5

I doubt the difference is really measurable, but in principle this should be better as it tries to just access the table without copying.

Comment on attachment 8908976 [details] [diff] [review] Use GetFontTable rather than CopyFontTable in gfxDWriteFontEntry::IsCJKFont() to try and avoid copying Review of attachment 8908976 [details] [diff] [review]: ----------------------------------------------------------------- Seems like strictly an improvement to me. ::: gfx/thebes/gfxDWriteFontList.cpp @@ +698,5 @@ > > mIsCJK = false; > > const uint32_t kOS2Tag = TRUETYPE_TAG('O','S','/','2'); > + hb_blob_t* blob = GetFontTable(kOS2Tag); nit: Maybe add a comment that if anyone adds any early return paths here they need to remember to call hb_blob_destroy? It's a shame we don't have an RAII class for this.

Pushed by jkew@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/98c159aec57e Use GetFontTable rather than CopyFontTable in gfxDWriteFontEntry::IsCJKFont() to try and avoid copying. r=bas