[llvm] [RISCV][VLOPT] Look through PHI instructions (PR #132236)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

@preames @topperc @lukel97 thanks for pointing this out. I've updated the patch to avoid an infinite loop. I think it is conservative in that case since the user in the loop body is causing us not to optimize. Maybe we can handle that in a follow up.

@lukel97 thanks for sharing your patch, I''ll take a closer look now.

https://github.com/llvm/llvm-project/pull/132236