[llvm] [LLVM][CodeGen][AArch64] Increase opportunities to fold shift-of-extend into sshll/ushll. (PR #213989)

[Ricardo Jesus via llvm-commits]

https://github.com/rj-jesus approved this pull request.

One query but otherwise looks good, cheers.

Is it worth having tests where both A and B are extended? To avoid potential regressions if multiply-long nodes are ever removed or formed later.

https://github.com/llvm/llvm-project/pull/213989