[llvm] [VPlan] Remove non-reductions after simplifications. (PR #176795)

[via llvm-commits]

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@@ -113,9 +113,9 @@ inline VPRecipeBase *findRecipe(VPValue *Start, PredT Pred) {
   for (unsigned I = 0; I != Worklist.size(); ++I) {
     VPValue *Cur = Worklist[I];
     auto *R = Cur->getDefiningRecipe();
-    // TODO: Skip live-ins once no degenerate reductions (ones with constant
-    // backedge values) are generated.
-    if (R && Pred(R))
+    if (!R)
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ayalz wrote:

The only Cur that may be free of having a defining recipe, is Start? If so, better peel and check that once, at the outset?

https://github.com/llvm/llvm-project/pull/176795