[llvm] [SLP]Model or-reduction of masked shifted lanes as a bitfield pack (PR #219731)

[Ryan Buchner via llvm-commits]

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

Left one code cleanup item [here](https://github.com/llvm/llvm-project/pull/219731/changes/68eab32d78b4e422ca62855eecd6d21e7473e6e7#r4011047029). After that LGTM, sorry for the delay in reviewing.

https://github.com/llvm/llvm-project/pull/219731