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

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

We could consider creating a TTI::ShuffleKindSet mask type and create the entire set in one call in the ShuffleVectorInst constructor - the ShuffleVectorInst::is*Mask calls are all very similar, it shouldn't take much to merge them all into a single analysis loop.

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