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

[Benjamin Maxwell via llvm-commits]

================
@@ -943,11 +943,23 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
       if (CI && !VFDatabase::getMappings(*CI).empty())
         VecCallVariantsFound = true;
 
+      auto canWidenInstruction = [](Instruction const & Inst) {
+        Type *InstTy = Inst.getType();
+        if (isa<CallInst>(Inst) && isa<StructType>(InstTy) &&
+            canWidenType(InstTy)) {
+          // For now, we can only widen struct values returned from calls where
+          // all users are extractvalue instructions.
+          return llvm::all_of(Inst.uses(), [](auto &Use) {
+            return isa<ExtractValueInst>(Use.getUser());
+          });
+        }
+        return VectorType::isValidElementType(InstTy) || InstTy->isVoidTy();
+      };
+
       // Check that the instruction return type is vectorizable.
       // We can't vectorize casts from vector type to scalar type.
       // Also, we can't vectorize extractelement instructions.
-      Type *InstTy = I.getType();
-      if (!(InstTy->isVoidTy() || canWidenType(InstTy)) ||
+      if (!canWidenInstruction(I) ||
----------------
MacDue wrote:

Why? I find having the helper return `true` when it can widen a little clearer

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