[clang] [CIR] Add support for derived class declarations (PR #142823)

[Erich Keane via cfe-commits]

================
@@ -32,3 +38,16 @@ CompleteC cc;
 // CIR:       cir.global external @cc = #cir.zero : !rec_CompleteC
 // LLVM:  @cc = global %class.CompleteC zeroinitializer
 // OGCG:  @cc = global %class.CompleteC zeroinitializer
+
+class Base {
+public:
+  int a;
+};
+
+class Derived : public Base {
+public:
+  int b;
+};
+
+int use(Derived *d) { return d->b; }
----------------
erichkeane wrote:

Can we get a CRTP test as well?  Something like:

```
template<typename Derived>
struct CRTP {
  Derived *otherDerived /* initializer left out, but add something to make sure this isn't ub */;
   void callThing() {
        static_cast<Derived>(*this)->thing();
        otherDerived->thing();
    }
};
struct D : CRTP<D> {
  void thing(){}
};

void use( D&d) {
   d.callThing();
}
```

I suspect it'll work fine, but its awkward enough with this sorta thing that it might be demonstrative.


https://github.com/llvm/llvm-project/pull/142823