[PATCH] D123408: [InstCombine] Limit folding of cast into PHI

[Bardia Mahjour via Phabricator via llvm-commits]

bmahjour added a comment.

The cleanest way I can think of to teach LoopVectorizer about this would be to introduce a whole new set of composite reduction operations of the form `<op>-then-<lop>` (eg `RecurKind::AddThenAnd`, `RecurKind::MulThenAnd`, `RecurKind::OrThenAnd`, and so on)...and that's just for combining logical `and` with the known integer reduction ops, so if we want to support e.g. `or` we'd need to double the number of additional recurrence kinds (and the extra logic that comes with it) again. The identity value would be determined from the `<op>` and the `<lop>` has to be applied when reducing the final vector into a single scalar upon loop exit.

@lebedev.ri is this what you had in mind or is there a better way to do it?


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https://reviews.llvm.org/D123408