CHECK_C_SOURCE_COMPILES("
#if __x86_64 || __x86_64__ || __amd64 || __AMD64 || _M_X64
// x86-64 target system
#else
#error Not building for x86-64
#endif
int main() {}
" HAVE_X86_64)

option(BLAKE2B_USE_SSE2 "Use SSE2 instructions for BLAKE2b" ${HAVE_X86_64})