[llvm] [X86][AMX] Check also AMX register live out for copy lowering (PR #93692)

[Nikita Popov via llvm-commits]

nikic wrote:

> I think a short term solution is to check `hasAMXTILE()` at the beginning. It would appears just well for these tests because I assume they won't enable AMX features but it takes no effect when compiling for targets have this feature.

This is fine, though maybe it would be better to copy the register check from X86FastPreTileConfig as well? Otherwise it may affect `-march=native` builds even though there is no AMX use.

> For long term solution, we do need a one time analysis for all passes. I like @aengelke 's ideas in #92910 and want this to be addressed together.
> 
> @nikic What do you think?

Sounds good!

https://github.com/llvm/llvm-project/pull/93692