libgreen context switching never swaps AVX registers, and SSE registers aren't handled on 32-bit

[thestinger]

We support flags to enable AVX and SSE, but it's broken because context switching doesn't handle it. The OS will detect the CPU and swap appropriately, but we don't.

[thestinger]

Nominating for production ready. It's not good to be generating invalid binaries from a non-experimental feature.

[graydon]

I have some fixes to this in the gc branch but likely more are required.

[thestinger]

This is still an issue.

[catamorphism]

Accepted for production-ready

[flaper87]

triage bump, nothing to add.

[pnkfelix]

cc me.

As part of my gc experiments I have played with the code graydon mentioned above. Probably should look into landing it or some variant of it independently of the GC work.

[pnkfelix]

P-low, not a 1.0 blocker; at worst we do not support enabling SSE until sometime after 1.0 release.

[thestinger]

#17325 means this is no longer relevant to the standard libraries