[Bug tree-optimization/61742] New: wrong code at -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61742

            Bug ID: 61742
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 4.10.0
            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 testcase on x86_64-linux at -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 20140707 (experimental) [trunk revision 212329] (GCC) 
$ 
$ gcc-trunk -O2 small.c; a.out
1
$ gcc-4.9 -O3 small.c; a.out
1
$ 
$ gcc-trunk -O3 small.c; a.out
0
$ 


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


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

int a, b, c, e, f, g, h, i, j, k;
int d[1];

int
main ()
{
  int l, m;
  k = 0;
  for (; g < 1; g++)
    {
      for (i = 0; i < 1; i++)
    m = b ? b : 1;
      if (m)
    j = d[e] = 0;
      else
    f = 0;
      l = k ? k : a;
      if (d[0] < 1)
    {
      c++;
      h = (l || e) > 0;
    }
    }
  printf ("%d\n", c);
  return 0;
}