clang/test/CodeGenCXX/vtable-constexpr.cpp

// RUN: %clang_cc1 -std=c++20 %s -emit-llvm -o - -triple %itanium_abi_triple | FileCheck %s --implicit-check-not=DoNotEmit

// constexpr virtual functions can be called at runtime and go in the vtable as
// normal. But they are implicitly inline so are never the key function.

struct DoNotEmit {
  virtual constexpr void f();
};
constexpr void DoNotEmit::f() {}

// CHECK-DAG: @_ZTV1B = {{.*}} constant { [3 x i8*] } { {{.*}} null, {{.*}} @_ZTI1B {{.*}} @_ZN1B1fEv
struct B {
  // CHECK-DAG: define {{.*}} @_ZN1B1fEv
  virtual constexpr void f() {}
};
B b;

struct CBase {
  virtual constexpr void f(); // not key function
};

// CHECK-DAG: @_ZTV1C = {{.*}} constant {{.*}} null, {{.*}} @_ZTI1C {{.*}} @_ZN1C1fEv
struct C : CBase {
  void f(); // key function
};
// CHECK-DAG: define {{.*}} @_ZN1C1fEv
void C::f() {}