Libco alternatives.

[ghost]

I found a potential replacement for libco though I am not 100% sure as to the veracity of its claims:
https://github.com/hnes/libaco
Also found another library by Tencent:
https://github.com/Tencent/libco/tree/v1.0
and this:
https://github.com/heiher/hev-task-system

libaco claims to be the fastest cothread library, while also having support for saving/restoring MMX/SSE/AVX state on x86/x64, which iirc byuu's libco doesn't have. The changes compared to libco on resulting cores haven't been profiled, though personally I am quite intrigued in seeing if on bsnes-mercury it helps, if even minutely.

[hizzlekizzle]

One of the SNES Mini guys says he has some homegrown better-than-libco cothread library, as well, which I am skeptical about, but it would be good to try the Tencent one and libaco, at least, I would think.

[inactive123]

I'm fine with libco alternatives being available in libretro-common.

[ghost]

One of the SNES Mini guys says he has some homegrown better-than-libco cothread library

I'd like to see some proof about that.