[polly] [Polly] Data flow reduction detection to cover more cases (PR #84901)

[Eli Friedman via llvm-commits]

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+; RUN: opt %loadPolly -basic-aa -polly-print-dependences -polly-allow-nonaffine -disable-output < %s | FileCheck %s
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efriedma-quic wrote:

`-passes=print<polly-dependences>` (see #92918).  I think legacy-pm -polly-print-scops wasn't ported yet, so it should be okay to continue using it for now.

Otherwise, patch looks fine.

https://github.com/llvm/llvm-project/pull/84901