[Bug target/50818] va_list is filled incorrectly in functions with ms_abi attribute on amd64

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50818

--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> ---
Executable testcase:

--cut here--
int
__attribute__((ms_abi))
foo (int n, ...)
{
  __builtin_va_list ap;
  int sum = 0;

  __builtin_va_start (ap, n);

  while (n--)
    sum += __builtin_va_arg (ap, int);

  __builtin_va_end (ap);

  return sum;
}

int main ()
{
  int res = foo (10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

  if (res != 55)
    __builtin_abort ();

  return 0;
}
--cut here--

$ gcc -O2 pr50818.c
$ ./a.out
Segmentation fault (core dumped)
$ gcc -O2 -mabi=ms pr50818.c
$ ./a.out
$