[llvm] [VFABI] Add support for vector functions that return struct types (PR #119000)

[David Sherwood via llvm-commits]

================
@@ -0,0 +1,32 @@
+//===----------- VectorUtils.h -  Vector type utility functions -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_VECTORUTILS_H
+#define LLVM_IR_VECTORUTILS_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/IR/DerivedTypes.h"
+
+namespace llvm {
+
+/// A helper function for converting Scalar types to vector types. If
+/// the incoming type is void, we return void. If the EC represents a
+/// scalar, we return the scalar type.
+inline Type *ToVectorTy(Type *Scalar, ElementCount EC) {
+  if (Scalar->isVoidTy() || Scalar->isMetadataTy() || EC.isScalar())
+    return Scalar;
+  return VectorType::get(Scalar, EC);
+}
+
+inline Type *ToVectorTy(Type *Scalar, unsigned VF) {
+  return ToVectorTy(Scalar, ElementCount::getFixed(VF));
+}
+
+} // namespace llvm
----------------
david-arm wrote:

This is just a suggestion, but how about putting declarations of `ToWideTy` and `ToNarrowTy` here, with the struct specific aspects living in `CallWideningUtils` (or whatever name we decide for the file). For example, you could have:

```
inline Type *ToWideTy(Type *Scalar, ElementCount EC) {
  if (isa<StructType>(Scalar))
    return ToWideStructTy(Scalar, EC);
  return ToVectorTy(Scalar, EC);
}
```

and something similarly for `ToNarrowTy`?

I like the separation of vectorisation of scalars and structs in different files though.

https://github.com/llvm/llvm-project/pull/119000