[llvm] [VPlan] Consolidate logic for narrowToSingleScalars (NFC) (PR #167360)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-vectorizers

Author: Ramkumar Ramachandra (artagnon)

<details>
<summary>Changes</summary>

The logic for narrowing to single scalar recipes is in two different places: narrowToSingleScalarRecipes and legalizeAndOptimizeInductions. Consolidate them.

---
Full diff: https://github.com/llvm/llvm-project/pull/167360.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp (+3-25) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index f5bef08fafcdc..77fd6203016ae 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -670,30 +670,6 @@ static void legalizeAndOptimizeInductions(VPlan &Plan) {
     if (!PhiR)
       continue;
 
-    // Try to narrow wide and replicating recipes to uniform recipes, based on
-    // VPlan analysis.
-    // TODO: Apply to all recipes in the future, to replace legacy uniformity
-    // analysis.
-    auto Users = collectUsersRecursively(PhiR);
-    for (VPUser *U : reverse(Users)) {
-      auto *Def = dyn_cast<VPSingleDefRecipe>(U);
-      auto *RepR = dyn_cast<VPReplicateRecipe>(U);
-      // Skip recipes that shouldn't be narrowed.
-      if (!Def || !isa<VPReplicateRecipe, VPWidenRecipe>(Def) ||
-          Def->getNumUsers() == 0 || !Def->getUnderlyingValue() ||
-          (RepR && (RepR->isSingleScalar() || RepR->isPredicated())))
-        continue;
-
-      // Skip recipes that may have other lanes than their first used.
-      if (!vputils::isSingleScalar(Def) && !vputils::onlyFirstLaneUsed(Def))
-        continue;
-
-      auto *Clone = new VPReplicateRecipe(Def->getUnderlyingInstr(),
-                                          Def->operands(), /*IsUniform*/ true);
-      Clone->insertAfter(Def);
-      Def->replaceAllUsesWith(Clone);
-    }
-
     // Replace wide pointer inductions which have only their scalars used by
     // PtrAdd(IndStart, ScalarIVSteps (0, Step)).
     if (auto *PtrIV = dyn_cast<VPWidenPointerInductionRecipe>(&Phi)) {
@@ -1418,7 +1394,9 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
       // Skip recipes that aren't single scalars or don't have only their
       // scalar results used. In the latter case, we would introduce extra
       // broadcasts.
-      if (!vputils::isSingleScalar(RepOrWidenR) ||
+      if ((!vputils::isSingleScalar(RepOrWidenR) &&
+           !vputils::onlyFirstLaneUsed(RepOrWidenR)) ||
+          RepOrWidenR->getNumUsers() == 0 ||
           !all_of(RepOrWidenR->users(), [RepOrWidenR](const VPUser *U) {
             if (auto *Store = dyn_cast<VPWidenStoreRecipe>(U)) {
               // VPWidenStore doesn't have users, and stores are always

``````````

</details>


https://github.com/llvm/llvm-project/pull/167360