[llvm] [RISCV][MC] Add support for experimental Zimop extension (PR #75182)

[Jivan Hakobyan via llvm-commits]

JivanH wrote:

@dtcxzyw
Here is the first patch of the series as you suggested. Next, I will send patches for lSel and builtins support.

@wangpc-pp 
I think the schedule/cost model depends on the vendors. Currently, I cannot add it because the latency for those instructions is not defined yet.

@topperc 
If I am not mistaken Zicfiss extension uses moprr instructions to get ROP functionality. But Zimop does not limit only the use of Zicfiss extension. They can be redefined and assigned other operations.



https://github.com/llvm/llvm-project/pull/75182