[Bug tree-optimization/61383] New: wrong code at -O2 and -O3 on x86_64-linux-gnu

["su at cs dot ucdavis.edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61383

            Bug ID: 61383
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: unknown
            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 (as well as gcc 4.8 and 4.9) miscompiles the following
code on x86_64-linux at -O2 and -O3 in both 32-bit and 64-bit modes.

This is a regression from 4.7.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 20140601 (experimental) [trunk revision 211110] (GCC) 
$ 
$ gcc-trunk -Os small.c; a.out
$ gcc-4.7.3 -O2 small.c; a.out
$ 
$ gcc-trunk -O2 small.c; a.out
Floating point exception (core dumped)
$ gcc-4.8.2 -O2 small.c; a.out
Floating point exception (core dumped)
$ 


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


int a, b = 1, c, d, e, f, g;

int
fn1 ()
{
  int h;
  for (;;)
    {
      g = b;
      g = g ? 0 : 1 % g;
      e = a + 1;
      for (; d < 1; d = e)
    {
      h = f == 0 ? 0 : 1 % f;
      if (f < 1)
        c = 0;
      else if (h)
        break;
    }
      if (b)
    return 0;
    }
}

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