Auto merge of #121138 - Swatinem:grapheme-extend-ascii, r= · rust-lang/rust@2d650c6 (original) (raw)

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Commit 2d650c6

Auto merge of #121138 - Swatinem:grapheme-extend-ascii, r=

Add ASCII fast-path for `char::is_grapheme_extended` I discovered that `impl Debug for str` is quite slow because it ends up doing a `unicode_data::grapheme_extend::lookup` for each char, which ends up doing a binary search. This introduces a fast-path for ASCII chars which do not have this property. The `lookup` is thus completely gone from profiles. --- As a followup, maybe it’s worth implementing this fast path directly in `unicode_data` so that it can check for the lower bound directly before going to a potentially expensive binary search.

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Original file line number Diff line number Diff line change
@@ -927,7 +927,7 @@ impl char {
927 927 #[must_use]
928 928 #[inline]
929 929 pub(crate) fn is_grapheme_extended(self) -> bool {
930 - unicode::Grapheme_Extend(self)
930 +self > '\x7f' && unicode::Grapheme_Extend(self)
931 931 }
932 932
933 933 /// Returns `true` if this `char` has one of the general categories for numbers.