They do not translate x87 to SSE/AVX under the hood. It's goofy enough, (not just with the extra precision, but the status word needs to be renamed too) that i

They do not translate x87 to SSE/AVX under the hood. It's goofy enough, (not just with the extra precision, but the status word needs to be renamed too) that it has dedicated hardware. Therefore there's a seperate register file that stores x87/mmx state (and avx-512 k mask registers). https://travisdowns.github.io/blog/2020/05/26/kreg2.html https://travisdowns.github.io/blog/2020/05/26/kreg2.html