[clang] [llvm] RFC: Implementing new mechanism for hard register operands to inline asm as a constraint. (PR #85846)

[Tony Tao via llvm-commits]

tltao wrote:

> If you do want to reject, please make sure we reject gracefully at both the clang level and the LLVM IR level.

Is there a reason we also need to check it in the LLVM IR level if we are already checking for it in clang? This PR only affects the Clang output so I don't know for sure if there's another path to generate the LLVM IR pattern. 

https://github.com/llvm/llvm-project/pull/85846