[llvm] [LV] Add initial support for vectorizing literal struct return values (PR #109833)

[Matt Arsenault via llvm-commits]

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@@ -399,13 +399,25 @@ void VPTransformState::setDebugLocFrom(DebugLoc DL) {
     Builder.SetCurrentDebugLocation(DIL);
 }
 
-void VPTransformState::packScalarIntoVectorValue(VPValue *Def,
-                                                 const VPLane &Lane) {
+void VPTransformState::packScalarIntoWideValue(VPValue *Def,
+                                               const VPLane &Lane) {
   Value *ScalarInst = get(Def, Lane);
-  Value *VectorValue = get(Def);
-  VectorValue = Builder.CreateInsertElement(VectorValue, ScalarInst,
-                                            Lane.getAsRuntimeExpr(Builder, VF));
-  set(Def, VectorValue);
+  Value *WideValue = get(Def);
+  Value *LaneExpr = Lane.getAsRuntimeExpr(Builder, VF);
+  if (auto *StructTy = dyn_cast<StructType>(WideValue->getType())) {
+    // We must handle each element of a widened struct type.
+    for (unsigned I = 0, E = StructTy->getNumElements(); I != E; I++) {
+      Value *ScalarValue = Builder.CreateExtractValue(ScalarInst, I);
+      Value *VectorValue = Builder.CreateExtractValue(WideValue, I);
+      VectorValue =
+          Builder.CreateInsertElement(VectorValue, ScalarValue, LaneExpr);
+      WideValue = Builder.CreateInsertValue(WideValue, VectorValue, I);
+    }
+  } else {
+    assert(WideValue->getType()->isVectorTy() && "expected vector type!");
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arsenm wrote:

I assume this is redundant with an assert inside of CreateInsertElement 

https://github.com/llvm/llvm-project/pull/109833