[Bug target/100758] __builtin_cpu_supports does not (always) detect "sse2"

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100758

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Erich Eckner from comment #17)
> With that, I get a segfault in cpuid():
> 
> (gdb) run
> Starting program: /tmp/a.out 
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/libthread_db.so.1".
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000555555555191 in cpuid ()
> (gdb) bt
> #0  0x0000555555555191 in cpuid ()
> #1  0x00005555555551ef in main ()
> (gdb) 
> 
> ... same on x86_64 - maybe, there's a typo, somewhere?

Sorry, wrote it without actually trying to compile it, I've swapped the last 2
arguments of cpuid.

Use
static void cpuid( unsigned int ax, unsigned int cx, unsigned int *p )
{
  unsigned int flags;

  __asm __volatile
    ("movl %%ebx, %%esi\n\t"
     "cpuid\n\t"
      "xchgl %%ebx, %%esi"
      : "=a" (p[0]), "=S" (p[1]),
      "=c" (p[2]), "=d" (p[3])
      : "0" (ax), "2" (cx));
}

int main() {
  unsigned int regs[4];
  for (int j=0; j<=18; j++) {
    int k = j > 10 ? -__INT_MAX__ - 1 + (j - 11) : j;
    cpuid( k, 0, regs );
    __builtin_printf("%d %d ", k, 0);
    for (int i=0; i<4; i++) {
      __builtin_printf("%08x ", regs[i]);
    }
    __builtin_printf("\n");
    cpuid( k, 1, regs );
    __builtin_printf("%d %d ", k, 1);
    for (int i=0; i<4; i++) {
      __builtin_printf("%08x ", regs[i]);
    }
    __builtin_printf("\n");
  }
  return 0;
}