[llvm] [Instructions] cache computed shufflevector properties (PR #115536)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

I didn't see any compile-time impact when testing this, but probably this needs a fairly specific workload to see benefits. Could you maybe provide some numbers on what you see?

In terms of implementation, I do wonder whether it would make sense to always compute the full properties on construction / mask change, as the lazy initialization makes this somewhat ugly.

https://github.com/llvm/llvm-project/pull/115536