[llvm] [Scalarizer][DirectX] support structs return types (PR #111569)

[Justin Bogner via llvm-commits]

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@@ -1208,6 +1274,35 @@ bool ScalarizerVisitor::finish() {
         Res = concatenate(Builder, CV, VS, Op->getName());
 
         Res->takeName(Op);
+      } else if (auto *Ty = dyn_cast<StructType>(Op->getType())) {
+        BasicBlock *BB = Op->getParent();
+        IRBuilder<> Builder(Op);
+        if (isa<PHINode>(Op))
+          Builder.SetInsertPoint(BB, BB->getFirstInsertionPt());
+
+        // Iterate over each element in the struct
+        unsigned NumOfStructElements = Ty->getNumElements();
+        SmallVector<ValueVector, 4> ElemCV(NumOfStructElements);
+        for (unsigned I = 0; I < NumOfStructElements; ++I) {
+          for (auto *CVelem : CV) {
+            Value *Elem = Builder.CreateExtractValue(
+                CVelem, I, Op->getName() + ".elem" + std::to_string(I));
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bogner wrote:

I think something like `Twine(Op->getName()) + ".elem" + I` might work here and be slightly more efficient than creating a `std::string`

https://github.com/llvm/llvm-project/pull/111569