[llvm] [ARM64EC] Warn on using disallowed registers in assembly src. (PR #93618)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo commented:

Thanks, this looks very valuable!

Can you mention how to enable this warning when using armasm64? (Or I guess it probably gets enabled automatically if assembling with some flag to switch to arm64ec mode - what's the armasm64 flag for that?)

https://github.com/llvm/llvm-project/pull/93618