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

[Luke Lau via llvm-commits]

https://github.com/lukel97 commented:

Do we need to somehow check the mask/vl? E.g. with this patch if we have a store with vl=0 and a load of vl=8 to the same pointer, does EarlyCSE still get rid of the load

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