libstdc++-v3/testsuite/26_numerics/bit/bit.count/countr_one.cc

   1 // Copyright (C) 2018-2022 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-options "-std=gnu++2a" }
  19 // { dg-do compile { target c++2a } }
  20
  21 #include <bit>
  22 #include <limits>
  23
  24 template<typename UInt>
  25 constexpr auto
  26 test(UInt x)
  27 -> decltype(std::countr_one(x))
  28 {
  29   static_assert( noexcept(std::countr_one(x)) );
  30
  31   constexpr unsigned digits = std::numeric_limits<UInt>::digits;
  32
  33   static_assert( std::countr_one((UInt)0) == 0 );
  34   static_assert( std::countr_one((UInt)-1) == digits );
  35   static_assert( std::countr_one((UInt)127) == 7 );
  36
  37   static_assert( std::countr_one((UInt)1) == 1 );
  38   static_assert( std::countr_one((UInt)3) == 2 );
  39   static_assert( std::countr_one((UInt)0x1f) == 5 );
  40   static_assert( std::countr_one((UInt)((UInt)-1 ^ 0x10)) == 4 );
  41
  42   if constexpr (std::numeric_limits<UInt>::digits > 8)
  43   {
  44     static_assert( std::countr_one((UInt)((UInt)-1 ^ 0x100)) == 8 );
  45     static_assert( std::countr_one((UInt)((UInt)-1 ^ 0x101)) == 0 );
  46   }
  47
  48   if constexpr (std::numeric_limits<UInt>::digits > 64)
  49   {
  50     static_assert( std::countr_one((UInt)-1 ^ ((UInt)1 << 70)) == 70 );
  51   }
  52
  53   return true;
  54 }
  55
  56 static_assert( test( (unsigned char)0 ) );
  57 static_assert( test( (unsigned short)0 ) );
  58 static_assert( test( (unsigned int)0 ) );
  59 static_assert( test( (unsigned long)0 ) );
  60 static_assert( test( (unsigned long long)0 ) );
  61
  62 // std::countr_one(T) shall not participate in overload resolution
  63 // unless T is an unsigned integer type.
  64 struct X { constexpr bool did_not_match() { return true; } };
  65 constexpr X test(...) { return X{}; }
  66 static_assert( test( (bool)0 ).did_not_match() );
  67 static_assert( test( (char)0 ).did_not_match() );
  68 static_assert( test( (int)0 ).did_not_match() );
  69 static_assert( test( (char16_t)0 ).did_not_match() );
  70 static_assert( test( (float)0 ).did_not_match() );
  71 static_assert( test( (void*)0 ).did_not_match() );
  72 static_assert( test( X{} ).did_not_match() );
  73 enum E : unsigned { e };
  74 static_assert( test( e ).did_not_match() );
  75
  76 #if !defined(__STRICT_ANSI__) && defined __SIZEOF_INT128__
  77 static_assert( test( (unsigned __int128)0 ) );
  78 static_assert( test( (__int128)0 ).did_not_match() );
  79 #endif
  80 #if defined(__GLIBCXX_TYPE_INT_N_0)
  81 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_0)0 ) );
  82 static_assert( test( (__GLIBCXX_TYPE_INT_N_0)0 ).did_not_match() );
  83 #endif
  84 #if defined(__GLIBCXX_TYPE_INT_N_1)
  85 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_1)0 ) );
  86 static_assert( test( (__GLIBCXX_TYPE_INT_N_1)0 ).did_not_match() );
  87 #endif
  88 #if defined(__GLIBCXX_TYPE_INT_N_2)
  89 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_2)0 ) );
  90 static_assert( test( (__GLIBCXX_TYPE_INT_N_2)0 ).did_not_match() );
  91 #endif
  92 #if defined(__GLIBCXX_TYPE_INT_N_3)
  93 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_3)0 ) );
  94 static_assert( test( (__GLIBCXX_TYPE_INT_N_3)0 ).did_not_match() );
  95 #endif
  96
  97 #include <cstddef>
  98 static_assert( test( (std::byte)0 ).did_not_match() );