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

[Florian Hahn via llvm-commits]

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@@ -1084,6 +1084,40 @@ void VPlanTransforms::simplifyRecipes(VPlan &Plan, Type &CanonicalIVTy) {
   }
 }
 
+static void convertToUniformRecipes(VPlan &Plan) {
+  auto TryToNarrow = [](VPBasicBlock *VPBB) {
+    for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB))) {
+      // Try to narrow wide and replicating recipes to uniform recipes, based on
+      // VPlan analysis.
+      auto *Def = dyn_cast<VPSingleDefRecipe>(&R);
+      if (!Def || !isa<VPReplicateRecipe, VPWidenRecipe>(Def) ||
+          !Def->getUnderlyingValue())
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fhahn wrote:

Yep we should be able to do that soon. I'll give it a try, need to see if we rely on the encoded facts that certain recipes are widened in various places.

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