[clang] [CIR] Add support for initializing classes with multiple vtables (PR #155275)

[Amr Hesham via cfe-commits]

================
@@ -126,6 +127,32 @@ static bool isInitializerOfDynamicClass(const CXXCtorInitializer *baseInit) {
   return baseClassDecl->isDynamicClass();
 }
 
+namespace {
+/// A visitor which checks whether an initializer uses 'this' in a
+/// way which requires the vtable to be properly set.
+struct DynamicThisUseChecker
+    : ConstEvaluatedExprVisitor<DynamicThisUseChecker> {
+  using super = ConstEvaluatedExprVisitor<DynamicThisUseChecker>;
+
+  bool usesThis = false;
+
+  DynamicThisUseChecker(const ASTContext &c) : super(c) {}
+
+  // Black-list all explicit and implicit references to 'this'.
+  //
+  // Do we need to worry about external references to 'this' derived
+  // from arbitrary code?  If so, then anything which runs arbitrary
----------------
AmrDeveloper wrote:

```suggestion
  // from arbitrary code? If so, then anything which runs arbitrary
```

https://github.com/llvm/llvm-project/pull/155275