[clang][Interp] Fix classifying __builtin_addressof() argument

It's an lvalue, so we need to use the classify() taking an expression.

Author: tbaederr

clang/lib/AST/Interp/InterpBuiltin.cpp

@@ -609,8 +609,8 @@ static bool interp__builtin_addressof(InterpState &S, CodePtr OpPC,
                                       const InterpFrame *Frame,
                                       const Function *Func,
                                       const CallExpr *Call) {
-  PrimType PtrT =
-      S.getContext().classify(Call->getArg(0)->getType()).value_or(PT_Ptr);
+  assert(Call->getArg(0)->isLValue());
+  PrimType PtrT = S.getContext().classify(Call->getArg(0)).value_or(PT_Ptr);
 
   if (PtrT == PT_FnPtr) {
     const FunctionPointer &Arg = S.Stk.peek<FunctionPointer>();

clang/test/AST/Interp/functions.cpp

@@ -473,6 +473,10 @@ namespace AddressOf {
 
   constexpr _Complex float F = {3, 4};
   static_assert(__builtin_addressof(F) == &F, "");
+
+  void testAddressof(int x) {
+    static_assert(&x == __builtin_addressof(x), "");
+  }
 }
 
 namespace std {