[clang] [llvm] Remove mmx 3dnow (PR #96246)

[James Y Knight via llvm-commits]

jyknight wrote:

> I'd prefer we rip off ALL the 3dnow/mmx bandaid in one big series of patches - and not split across the 19.X/20.X releases.

The 3dnow part is a lot easier -- because it's not trying to be compatible, just dropping support entirely. And I don't think anyone will care, since 3dnow is effectively never used (even before it was discontinued in 2010, it was barely used).

For that same reason -- that it's unused and nobody will notice -- I also think there's not really a reason to wait on removing 3dnow support until other MMX changes are done.

> So can we get all the mmx patches done in time for the 19.0 branch?

Maybe? Depends on how the discussion on the other PR goes -- whether that proposal is acceptable, or if a different transition strategy is desired.

https://github.com/llvm/llvm-project/pull/96246