[Coroutines] Support opaque pointers in solveTypeName()

As far as I can tell, these names are only intended to be
informative, so just use a generic "PointerType" for opaque pointers.

The code in solveDIType() also treats pointers as basic types (and
does not try to encode the pointed-to type further), so I believe
this should be fine.

Differential Revision: https://reviews.llvm.org/D121280

llvm/lib/Transforms/Coroutines/CoroFrame.cpp

@@ -808,9 +808,10 @@ static StringRef solveTypeName(Type *Ty) {
     return "__floating_type_";
   }
 
-  if (Ty->isPointerTy()) {
-    auto *PtrTy = cast<PointerType>(Ty);
-    Type *PointeeTy = PtrTy->getPointerElementType();
+  if (auto *PtrTy = dyn_cast<PointerType>(Ty)) {
+    if (PtrTy->isOpaque())
+      return "PointerType";
+    Type *PointeeTy = PtrTy->getNonOpaquePointerElementType();
     auto Name = solveTypeName(PointeeTy);
     if (Name == "UnknownType")
       return "PointerType";