[llvm] [VectorCombine] isExtractExtractCheap - specify the extract/insert shuffle mask to improve shuffle costs (PR #114780)

[David Green via llvm-commits]

https://github.com/davemgreen approved this pull request.

Thanks. Lets go with this version and I might try and change the AArch64 cost model if I can come up with something sensible.

https://github.com/llvm/llvm-project/pull/114780