text: // Copyright (c) 2021, Tom Westerhout
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are met:
  //
  // * Redistributions of source code must retain the above copyright notice, this
  //   list of conditions and the following disclaimer.
  //
  // * Redistributions in binary form must reproduce the above copyright notice,
  //   this list of conditions and the following disclaimer in the documentation
  //   and/or other materials provided with the distribution.
  //
  // * Neither the name of the copyright holder nor the names of its
  //   contributors may be used to endorse or promote products derived from
  //   this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #include "lattice_symmetries/lattice_symmetries.h"
  #include <pthread.h>
  
  typedef struct ls_arch_flags {
      bool has_avx2;
      bool has_avx;
      bool has_sse4;
  } ls_arch_flags;
  
  static ls_arch_flags  cpu_info              = {false, false, false};
  static pthread_once_t cpu_info_once_control = PTHREAD_ONCE_INIT;
  
  static void init_cpu_info(void)
  {
      __builtin_cpu_init();
      cpu_info.has_avx2 = __builtin_cpu_supports("avx2") > 0;
      cpu_info.has_avx  = __builtin_cpu_supports("avx") > 0;
      cpu_info.has_sse4 =
          __builtin_cpu_supports("sse4.1") > 0 && __builtin_cpu_supports("sse4.2") > 0;
  }
  
  // cppcheck-suppress unusedFunction
  LATTICE_SYMMETRIES_EXPORT bool ls_has_avx2()
  {
      pthread_once(&cpu_info_once_control, &init_cpu_info);
      return cpu_info.has_avx2;
  }
  
  // cppcheck-suppress unusedFunction
  LATTICE_SYMMETRIES_EXPORT bool ls_has_avx()
  {
      pthread_once(&cpu_info_once_control, &init_cpu_info);
      return cpu_info.has_avx2;
  }
  
  // cppcheck-suppress unusedFunction
  LATTICE_SYMMETRIES_EXPORT bool ls_has_sse4()
  {
      pthread_once(&cpu_info_once_control, &init_cpu_info);
      return cpu_info.has_avx2;
  }
  