Comment by ngzhian

If you are using Emscripten, porting x86 should be easy (see https://emscripten.org/docs/porting/simd.html#compiling-simd...), but you will take some performance hits (like float min/max) and these are all documented in the links above.

If you are interested to bring more SIMD instructions, you can participate in the SIMD subgroup. What's needed is interest in suggesting new instructions, working on a proposal (following the process) and pushing it through. Compiler expertise not required :)