[llvm] [RISCV] Initial support for EarlyCSE (PR #138812)

[Hank Chang via llvm-commits]

HankChang736 wrote:

> Maybe the title should mention vector memory intrinsic? the EarlyCSE still work for RISC-V before, but just not work with those RISC-V specific memory intrinsic.

@kito-cheng Thank you for the feedback. Yeah, I think it's better to mention RISC-V specific memory intrinsics. Will update it later.

https://github.com/llvm/llvm-project/pull/138812