[llvm] [VPlan] Use ResumePhi to create reduction resume phis. (PR #110004)

[via llvm-commits]

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@@ -7561,67 +7561,53 @@ static void addRuntimeUnrollDisableMetaData(Loop *L) {
   }
 }
 
-// Check if \p RedResult is a ComputeReductionResult instruction, and if it is
-// create a merge phi node for it.
-static void createAndCollectMergePhiForReduction(
-    VPInstruction *RedResult,
-    VPTransformState &State, Loop *OrigLoop, BasicBlock *LoopMiddleBlock,
-    bool VectorizingEpilogue) {
+// If \p R is a ComputeReductionResult when vectorizing the epilog loop,
+// update the reduction's scalar PHI node by adding the incoming value from the
+// main vector loop.
+static void updateMergePhiForReductionForEpilogueVectorization(
+    VPRecipeBase *R, VPTransformState &State, Loop *OrigLoop,
+    BasicBlock *LoopMiddleBlock) {
+  auto *RedResult = dyn_cast<VPInstruction>(R);
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ayalz wrote:

```suggestion
  auto *EpiRedResult = dyn_cast<VPInstruction>(R);
```
would be good to keep Epi/Main names consistent.

https://github.com/llvm/llvm-project/pull/110004