[llvm] [AArch64] Combine getActiveLaneMask with vector_extract (PR #81139)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

Sorry for the delay.  To me it looks like you're doing type legalisation as a DAG Combine, which while a similar crime is being committed for fixed length types I don't think you should repeat because it will prevent any legitimate DAG combines.  Custom type legalisation really belongs in `ReplaceNodeResults`.

https://github.com/llvm/llvm-project/pull/81139