There's nothing to prevent this from being implemented, other than it'd be a huge hacky mess. It would require sidestepping iconv (or however grep does it) when

There's nothing to prevent this from being implemented, other than it'd be a huge hacky mess. It would require sidestepping iconv (or however grep does it) when LC_ALL is one of a specific set of strings, activating some special cases, and then additionally, building on those special cases, further scanning the input pattern (which may not just be a literal string - how might this work with character classes/ranges?) to ensure it is 7bit, in order to achieve the desired speedup. Or if your input data is sufficiently ASCII-ish, and so is your search pattern, then why not just force the process locale to C and avoid the whole mess to begin with. I'm suddenly left wondering how the "." regex syntax functions in the face of surrogates when handling UTF-8.