[Bug tree-optimization/69376] New: wrong code at -Os and above on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69376

            Bug ID: 69376
           Summary: wrong code at -Os and above on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -Os
and above in both 32-bit and 64-bit modes. 

This is a regression from 5.3.x.


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20160119 (experimental) [trunk revision 232571] (GCC) 
$ 
$ gcc-trunk -O1 small.c; ./a.out
$ gcc-5.3 -Os small.c; ./a.out
$ 
$ gcc-trunk -Os small.c
$ ./a.out
Segmentation fault (core dumped)
$ 


-----------------------------------------


int printf (const char *, ...); 

unsigned a, c, *d, f;
char b, e;
short g;

void
fn1 ()
{
  unsigned h = 4294967290;
  if (b >= 0)
    {
      h = b;
      c = b / 290;
      f = ~(c - (8 || h));
      if (f)
        printf ("%d\n", 1);
      if (f)
        printf ("%d\n", f);
      g = ~f;
      if (c < 3)
        {
          int i = -h < ~c;
          unsigned j;
          if (i)
            j = h;
          h = -j * g;
        }
      c = h;
    }
  unsigned k = ~h;
  char l = e || g;
  if (l < 1 || k < 7)
    *d = a;
}

int
main ()
{
  fn1 ();
  return 0;
}