I merged a few PRs to SIMD optimize Wasm WASI libc, but it all got stalled in str(c)spn (which is slightly more sophisticated than the rest).
There wasn't much appetite for any of it on Emscripten.
https://github.com/WebAssembly/wasi-libc/pulls?q=is%3Apr+opt...
subscribed to the str(c)spn thread for the eventual explanation of why the non-simd version seemed to give the wrong answer