[llvm] [LoopInterchange] Support inner-loop simple reductions via UndoSimpleReduction (PR #172970)

[Ryotaro Kasuga via llvm-commits]

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@@ -0,0 +1,86 @@
+; NOTE: Support simple reduction in the inner loop by undoing the simple reduction.
+; RUN: opt < %s -passes="loop(loop-interchange),dce"  -undo-simple-reduction -loop-interchange-profitabilities=ignore -S | FileCheck %s
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kasuga-fj wrote:

```suggestion
; RUN: opt < %s -passes="loop-interchange"  -undo-simple-reduction -loop-interchange-profitabilities=ignore -S | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/172970