test/FrontendC++/2010-03-22-empty-baseclass.cpp

   1 // RUN: %llvmgxx -S -emit-llvm %s -o - -O2 | FileCheck %s
   2 namespace boost {
   3   namespace detail {
   4     template <typename T> struct cv_traits_imp {};
   5     template <typename T> struct cv_traits_imp<T*> {typedef T unqualified_type;};
   6   }
   7 }
   8 namespace mpl_ {}
   9 namespace boost {
  10   namespace mpl {using namespace mpl_;}
  11   template< typename T > struct remove_cv {typedef typename boost::detail::cv_traits_imp<T*>::unqualified_type type;};
  12   namespace type_traits {
  13     typedef char yes_type;
  14     struct no_type {char padding[8];};
  15   }
  16 }
  17 namespace mpl_ {
  18   template< bool C_ > struct bool_;
  19   typedef bool_<true> true_;
  20   typedef bool_<false> false_;
  21   template< bool C_ > struct bool_ {static const bool value = C_;};
  22   template< typename T, T N > struct integral_c;
  23 }
  24 namespace boost{
  25   template <class T, T val>   struct integral_constant :
  26     public mpl::integral_c<T, val> {};
  27   template<> struct integral_constant<bool,true> : public mpl::true_ {};
  28   template<> struct integral_constant<bool,false> : public mpl::false_ {};
  29   namespace type_traits {
  30     template <bool b1, bool b2, bool b3 = false, bool b4 = false,
  31               bool b5 = false, bool b6 = false, bool b7 = false> struct ice_or;
  32     template <bool b1, bool b2, bool b3, bool b4, bool b5, bool b6, bool b7>
  33     struct ice_or {static const bool value = true; };
  34     template <> struct ice_or<false, false, false, false, false, false, false>
  35     {static const bool value = false;};
  36     template <bool b1, bool b2, bool b3 = true, bool b4 = true, bool b5 = true,
  37               bool b6 = true, bool b7 = true> struct ice_and;
  38     template <bool b1, bool b2, bool b3, bool b4, bool b5, bool b6, bool b7>
  39     struct ice_and {static const bool value = false;};
  40     template <> struct ice_and<true, true, true, true, true, true, true>
  41     {static const bool value = true;};
  42     template <bool b> struct ice_not {static const bool value = true;};
  43   };
  44   namespace detail {
  45     template <typename T> struct is_union_impl {static const bool value = false;};
  46   }
  47   template< typename T > struct is_union :
  48   ::boost::integral_constant<bool, ::boost::detail::is_union_impl<T>::value> {};
  49   namespace detail {
  50     template <class U> ::boost::type_traits::yes_type is_class_tester(void(U::*)(void));
  51     template <class U> ::boost::type_traits::no_type is_class_tester(...);
  52     template <typename T> struct is_class_impl {
  53       static const bool value = (::boost::type_traits::ice_and< sizeof(is_class_tester<T>(0))
  54                                  == sizeof(::boost::type_traits::yes_type),
  55                                  ::boost::type_traits::ice_not< ::boost::is_union<T>::value >::value >::value);};
  56 }
  57   template<typename T> struct is_class:
  58   ::boost::integral_constant<bool,::boost::detail::is_class_impl<T>::value> {  };
  59 namespace detail {
  60   template <typename T> struct empty_helper_t1: public T {int i[256];};
  61   struct empty_helper_t2 {int i[256];};
  62   template <typename T, bool is_a_class = false> struct empty_helper
  63   {static const bool value = false;};
  64   template <typename T> struct empty_helper<T, true>
  65   {static const bool value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2));};
  66   template <typename T> struct is_empty_impl {
  67     typedef typename remove_cv<T>::type cvt;
  68     static const bool value = (::boost::type_traits::ice_or< ::boost::detail::empty_helper
  69                                <cvt,::boost::is_class<T>::value>::value, false>::value);
  70   };
  71 }
  72 template<typename T> struct is_empty:
  73 ::boost::integral_constant<bool,::boost::detail::is_empty_impl<T>::value> {};
  74 template<typename T, typename U > struct is_same:
  75 ::boost::integral_constant<bool,false> {};
  76 template<typename T> struct call_traits {typedef T& reference;};
  77 namespace details {
  78   template <class T1, class T2, bool IsSame, bool FirstEmpty, bool SecondEmpty>
  79   struct compressed_pair_switch;
  80   template <class T1, class T2>
  81   struct compressed_pair_switch<T1, T2, false, true, false>
  82   {static const int value = 1;};
  83   template <class T1, class T2, int Version> class compressed_pair_imp;
  84   template <class T1, class T2> class compressed_pair_imp<T1, T2, 1>:
  85   protected ::boost::remove_cv<T1>::type {
  86   public:
  87     typedef T1 first_type;
  88     typedef T2 second_type;
  89     typedef typename call_traits<first_type>::reference first_reference;
  90     typedef typename call_traits<second_type>::reference second_reference;
  91     first_reference first() {return *this;}
  92     second_reference second() {return second_;}
  93     second_type second_;
  94   };
  95 }
  96 template <class T1, class T2> class compressed_pair:
  97   private ::boost::details::compressed_pair_imp<T1, T2, ::boost::details::compressed_pair_switch<
  98                                                           T1, T2, ::boost::is_same<typename remove_cv<T1>::type,
  99                                                                                    typename remove_cv<T2>::type>::value,
 100                                                           ::boost::is_empty<T1>::value, ::boost::is_empty<T2>::value>::value>
 101   {
 102   private:
 103     typedef details::compressed_pair_imp<T1, T2, ::boost::details::compressed_pair_switch<
 104                                                    T1, T2, ::boost::is_same<typename remove_cv<T1>::type,
 105                                                                             typename remove_cv<T2>::type>::value,
 106                                                                               ::boost::is_empty<T1>::value, ::boost::is_empty<T2>::value>::value> base;
 107   public:
 108     typedef T1 first_type;
 109     typedef T2 second_type;
 110     typedef typename call_traits<first_type>::reference first_reference;
 111     typedef typename call_traits<second_type>::reference second_reference;
 112     first_reference first() {return base::first();}
 113     second_reference second() {return base::second();}
 114   };
 115 }
 116 struct empty_base_t {};
 117 struct empty_t : empty_base_t {};
 118 typedef boost::compressed_pair<empty_t, int> data_t;
 119 extern "C" {int printf(const char * , ...);}
 120 extern "C" {void abort(void);}
 121 int main (int argc, char * const argv[]) {
 122   data_t x;
 123   x.second() = -3;
 124   // This store should be elided:
 125   x.first() = empty_t();
 126   // If x.second() has been clobbered by the elided store, fail.
 127   if (x.second() != -3) {
 128     printf("x.second() was clobbered\n");
 129     // CHECK-NOT: x.second() was clobbered
 130     abort();
 131   }
 132   return 0;
 133 }
 134 // CHECK: ret i32