[llvm] [X86] Fold BLEND(PERMUTE(X), PERMUTE(Y)) -> PERMUTE(BLEND(X, Y)) (PR #90219)

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dyung wrote:

Hi @RKSimon, we are seeing the compiler get into a seemingly infinite loop while compiling after this change. I have put a repro in #91433. Can you take a look?

https://github.com/llvm/llvm-project/pull/90219