[Bug tree-optimization/62151] New: wrong code at -O2 and -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62151

            Bug ID: 62151
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -O2
and -O3 in both 32-bit and 64-bit modes.

This is a regression from 4.9.x. 

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
Target: x86_64-unknown-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 4.10.0 20140814 (experimental) [trunk revision 213937] (GCC) 
$ 
$ gcc-trunk -Os small.c; a.out
$ gcc-4.9 -O2 small.c; a.out
$     
$ gcc-trunk -O2 small.c; a.out
Aborted (core dumped)
$ gcc-trunk -O3 small.c; a.out
Aborted (core dumped)
$ 


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


int a, c, d, e, f, g, h, i;
short b;

int
fn1 ()
{
  b = 0;
  for (;;)
    {
      int j[2];
      j[f] = 0;
      if (h)
    d = 0;
      else
    {
      for (; f; f++)
        ;
      for (a = 0; a < 1; a++)
        for (;;)
          {
        i = b & ((b ^ 1) & 83647) ? b : b - 1;
        g = 1 ? i : 0;
        e = j[0];
        if (c)
          break;
        return 0;
          }
    }
    }
}

int
main ()
{
  fn1 ();
  if (g != -1) 
    __builtin_abort (); 
  return 0;
}