[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

[Craig Topper via cfe-commits]

topperc wrote:

> > I guess Zaamo + Zacas is technically a way one could implement atomics without LR/SC?
> 
> The Zacas extension depends upon the A extension.

I filed an issue asking about that https://github.com/riscv/riscv-zaamo-zalrsc/issues/5

https://github.com/llvm/llvm-project/pull/77424