[llvm] [VPlan] Add narrowToSingleScalarRecipe transform. (PR #139150)

[via llvm-commits]

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@@ -1086,6 +1086,40 @@ void VPlanTransforms::simplifyRecipes(VPlan &Plan, Type &CanonicalIVTy) {
   }
 }
 
+static void convertToUniformRecipes(VPlan &Plan) {
+  if (Plan.hasScalarVFOnly())
+    return;
+
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
+           vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
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ayalz wrote:

Worth a comment. This also prevents narrowing recipes in nested loop regions.

https://github.com/llvm/llvm-project/pull/139150