[llvm] [VPlan] Support struct return types for widen intrinsics (NFC). (PR #165218)

[Benjamin Maxwell via llvm-commits]

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@@ -4100,7 +4100,22 @@ static bool willGenerateVectors(VPlan &Plan, ElementCount VF,
       Type *ScalarTy = TypeInfo.inferScalarType(ToCheck);
       if (!Visited.insert({ScalarTy}).second)
         continue;
-      Type *WideTy = toVectorizedTy(ScalarTy, VF);
+      Type *WideTy;
+      if (auto *WI = dyn_cast<VPWidenIntrinsicRecipe>(&R);
+          WI && ScalarTy->isStructTy()) {
+        auto *StructTy = cast<StructType>(ScalarTy);
+        SmallVector<Type *, 2> Tys;
+        for (unsigned I = 0, E = StructTy->getNumElements(); I != E; ++I) {
+          Type *ElementTy = StructTy->getStructElementType(I);
+          if (!isVectorIntrinsicWithStructReturnScalarAtField(
+                  WI->getVectorIntrinsicID(), I))
+            ElementTy = toVectorizedTy(ElementTy, VF);
+          Tys.push_back(ElementTy);
+        }
+        WideTy = StructType::create(Tys);
+      } else
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MacDue wrote:

This should be part of the `toVectorizedTy` helper, as otherwise the helper is pointless as it can't return a vectorized type. 

https://github.com/llvm/llvm-project/pull/165218