[clang] [llvm] [RISCV][clang] Support XSfmm ABI attributes (PR #206260)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

Do we have a plan for compiler-inserted library function calls?  Like, what happens when the compiler generates llvm.memcpy for struct assignment?

https://github.com/llvm/llvm-project/pull/206260