I guess I stand corrected. I was under the impression that C compilers don't tend to use it anymore when compiling for amd64. (Because you can assume SSE support on amd64, unlike a binary that might run on an old Pentium.) Then I misread that situation as it not working.
It does take effort for an OS kernel to save and restore x87 state, so I could imagine somebody dropping support.
> It does take effort for an OS kernel to save and restore x87 state, so I could imagine somebody dropping support.
FXSAVE saves the x87 state with the SSE state, and XSAVE generalizes that to add several optional components, depending on what your processor support (as of right now, AVX state, MPX state, 3 for AVX-512, PT state, and SGX state, IIRC).
It does take effort for an OS kernel to save and restore x87 state, so I could imagine somebody dropping support.