[llvm] [VPlan] Impl VPlan-based pattern match for ExtendedRed and MulAccRed (NFCI) (PR #113903)

[Florian Hahn via llvm-commits]

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@@ -1263,10 +1264,17 @@ void VPlanTransforms::clearReductionWrapFlags(VPlan &Plan) {
     if (RK != RecurKind::Add && RK != RecurKind::Mul)
       continue;
 
-    for (VPUser *U : collectUsersRecursively(PhiR))
+    for (VPUser *U : collectUsersRecursively(PhiR)) {
+      // Flags in reduction recipes are control/store by the recurrence
+      // descriptor. Dropping flags for VPExtendedReductionRecipe and
+      // VPMulaccRecipe may drop flags that we don't expect to drop.
+      if (isa<VPReductionRecipe>(U))
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fhahn wrote:

What case is this covering? If it is using VPRecipeWithIRFlags to manage flags, they should be dropped here as needed I think?

https://github.com/llvm/llvm-project/pull/113903