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

[Kito Cheng via llvm-commits]

kito-cheng 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.

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