[llvm] [SLP]Model gathers of extracted integer sub-fields as bitcast+permute+ext (PR #224919)

[Ryan Buchner via llvm-commits]

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

LGTM, I ran extra tests trying to exploit the pattern match logic but it seems to be robust.

https://github.com/llvm/llvm-project/pull/224919