[llvm] [SPARC] Accept named register aliases (PR #212838)

[via llvm-commits]

koachan wrote:

> Not near a computer now so I can't check, but I suppose IAS already accepts the `%rX` form too like GNU binutils?

Finally got the time to do it, seems like IAS already accepts `%rX` form too so this is not an issue.

> @koachan it was discovered by attempt to build clisp which failed as:
> 
> ```
> error: <unknown>:0:0: invalid register "%sp" for llvm.read_register
> ```

Ah, I see, so it's inline asm...

https://github.com/llvm/llvm-project/pull/212838