[llvm] InstSimplify: lookthru casts, binops in folding shuffles (PR #92668)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> You cannot RAUW inside InstSimplify. InstSimplify is an analysis, it cannot change IR in any way.

Oh no. Looks like I have to clone the entire chain of instructions, make the replacement in the new head instruction, and return the new tail? Is InstSimplify poorly-suited for this kind of change, and should I just leave it up to VectorCombine?

https://github.com/llvm/llvm-project/pull/92668