[llvm] [LoopInterchange] Handle PHI nodes in inner loop preheader (PR #196691)

[Ryotaro Kasuga via llvm-commits]

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@@ -2019,6 +2019,19 @@ bool LoopInterchangeTransform::transform(
   // instructions outside the loop nest.
   BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
   BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
+
+  // check if there are any Single path Phi Nodes in InnerLoop-Pre Header
+
+  if (InnerLoopPreHeader && InnerLoopPreHeader != OuterLoopHeader) {
+
+    for (PHINode &P : make_early_inc_range(InnerLoopPreHeader->phis())) {
+      if (P.getNumIncomingValues() == 1) {
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kasuga-fj wrote:

IIUC, `P` should not have more than one incoming values here because such cases would have been rejected in earlier stages. If that's the case, maybe adding an assert `P.getNumIncommingValues() == 1` would be better than if-statement.

https://github.com/llvm/llvm-project/pull/196691