Auto merge of rust-lang#121138 - Swatinem:grapheme-extend-ascii, r=<try>

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.
rust-lang-ci · Feb 20, 2024 · 2d650c6 · 2d650c6
2 parents bb86353 8eaaa6e
commit 2d650c6
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/library/core/src/char/methods.rs b/library/core/src/char/methods.rs
@@ -927,7 927,7 @@ impl char {
  #[must_use]
  #[inline]
  pub(crate) fn is_grapheme_extended(self) -> bool {
- unicode::Grapheme_Extend(self)
  self > '\x7f' && unicode::Grapheme_Extend(self)
  }
 
  /// Returns `true` if this `char` has one of the general categories for numbers.