Eh? PCMPISTRI has a few different modes of operation, including full substring search and character classes. e.g., You can use PCMPISTRI on a needle that contains adjacent classes. For example, `azAZ09` would check if any byte in the search string is in any of the ranges a-z, A-Z and 0-9.

Regardless, in the OP, they're specifically looking for one of a small number of bytes, which is exactly what PCMPISTRI is supposed to be good for.

With that said, my experience mirrors glangdale's. Every time I've tried to use PCMPISTRI, it's either been slower than other methods or not enough of an improvement to justify it.