[Bug tree-optimization/63659] 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=63659

            Bug ID: 63659
           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 (as well as 4.8.x and 4.9.x) 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/5.0.0/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 5.0.0 20141025 (experimental) [trunk revision 216691] (GCC) 

$ gcc-trunk -Os small.c; a.out
$ gcc-4.7 -O2 small.c; a.out
$ 
$ gcc-trunk -O2 small.c
$ ./a.out
Aborted (core dumped)
$     


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


int a, b, c, *d = &b, g, h, i;
unsigned char e;
char f;

int
main ()
{
  for (; a;)
    {
      for (a = 0; a; a++)
    for (; c; c++)
      ;
      if (i)
    break;
    }
  char j = c, k = -1, l;
  l = g = j >> h;
  f = l == 0 ? k : k % l;
  e = 0 ? 0 : f;
  *d = e;

  if (b != 255) 
    __builtin_abort (); 

  return 0;
}