[brucethemoose2]

The extensions can be kinda broken down into 4 levels. Basically ancient, old (SSE 4.2), reasonably new (AVX2, Haswell/Zen 1 and up), and baseline AVX512.

https://developers.redhat.com/blog/2021/01/05/building-red-h...

There is discussion of a fifth level. Someone in the Intel Clear Linux IRC said a fifth level wasn't "worth it" for Sapphire Rapids because most of the new AVX512 extensions were not autovectorized by compilers, but that a new level would be needed in the future. Perhaps they were thinking of APX, but couldn't disclose it.

[jcranmer]

AVX10/APX does sound like a good baseline for v5.

[Bulat_Ziganshin]

except that it doesn't support full AVX-512, making the whole idea of backward compatibility between these levels meaningless. "It's Intel!!!"

[brucethemoose2]

Well that's an even better justification, as a x86-64-v5 level would be needed for the newer CPUs.

We can throw away any hope of v4 being a standard baseline.