[llvm] [LoopVectorize] Support vectorization of frexp intrinsic (PR #172957)

[Benjamin Maxwell via llvm-commits]

================
@@ -1695,8 +1695,18 @@ void VPWidenIntrinsicRecipe::execute(VPTransformState &State) {
 
   SmallVector<Type *, 2> TysForDecl;
   // Add return type if intrinsic is overloaded on it.
-  if (isVectorIntrinsicWithOverloadTypeAtArg(VectorIntrinsicID, -1, State.TTI))
-    TysForDecl.push_back(VectorType::get(getResultType(), State.VF));
+  if (isVectorIntrinsicWithOverloadTypeAtArg(VectorIntrinsicID, -1,
+                                             State.TTI)) {
+    // If the return type is a struct, we need to unpack its elements and
+    // vectorize them individually for the overloaded declaration.
+    Type *RetTy = getResultType();
+    if (auto *ST = dyn_cast<StructType>(RetTy)) {
+      for (Type *ElemTy : ST->elements())
+        TysForDecl.push_back(VectorType::get(ElemTy, State.VF));
+    } else {
+      TysForDecl.push_back(VectorType::get(RetTy, State.VF));
+    }
----------------
MacDue wrote:

nit: I think you may be able to use the existing helpers for this:
```c++  
Type *RetTy =  toVectorizedTy(getResultType(), State.VF)
append_range(TysForDecl, getContainedTypes(RetTy));
```

https://github.com/llvm/llvm-project/pull/172957