[llvm] [VPlan] Extract reverse mask from reverse accesses (PR #155579)

[Luke Lau via llvm-commits]

https://github.com/lukel97 commented:

Sorry for the delay in the review, generally looks good. Just have one question about the legacy cost model workaround.

> I’m not sure whether these checks will become much more complicated once vp.reverse is replaced by splice + llvm.reverse.

I'm currently working on removing vp.reverse, I think these checks should all become simpler because we only need to check for llvm.reverse


https://github.com/llvm/llvm-project/pull/155579