[llvm] [RISCV] Support isel for Zacas for 2*XLen types. (PR #77814)

[Craig Topper via llvm-commits]

topperc wrote:

> This change isn't OK - we shouldn't add any new expansions of Load to CmpXChg. Unless there is an atomic 128-bit load operation also available in RISC-V, we cannot use amocas.q for implementing atomics.

There is no 128-bit atomic load for RISC-V currently defined


https://github.com/llvm/llvm-project/pull/77814