[Bug c/47148] New: likely wrong code bug

[regehr at cs dot utah.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47148

           Summary: likely wrong code bug
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: reg...@cs.utah.edu
                CC: cheny...@cs.utah.edu
              Host: x86_64-unknown-linux-gnu
            Target: x86_64-unknown-linux-gnu
             Build: x86_64-unknown-linux-gnu


[reg...@gamow tmp436]$ current-gcc -O1 small.c -o small 
[reg...@gamow tmp436]$ ./small
0
[reg...@gamow tmp436]$ current-gcc -O2 small.c -o small
[reg...@gamow tmp436]$ ./small
1
[reg...@gamow tmp436]$ current-gcc -v
Using built-in specs.
COLLECT_GCC=current-gcc
COLLECT_LTO_WRAPPER=/uusoc/exports/scratch/regehr/z/compiler-install/gcc-r168380-install/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.6.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --with-libelf=/usr/local --enable-lto
--prefix=/home/regehr/z/compiler-install/gcc-r168380-install
--program-prefix=r168380- --enable-languages=c,c++
Thread model: posix
gcc version 4.6.0 20101231 (experimental) (GCC) 
[reg...@gamow tmp436]$ cat small.c


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

static unsigned div(unsigned p1, unsigned p2)
{
  return p1 / p2;
}

static unsigned rshift (unsigned p1, unsigned p2)
{
  if (p2 >= 32)
    return p1;
  else
    return p1 >> p2;
}

static unsigned g_26 = 1;
static unsigned g_78 = 1;

static void func_28 (unsigned char p_30, unsigned p_31)
{
  if (p_31) {
    unsigned l1 = div (0x7000, p_30-2) ^ g_26;
    unsigned l2 = rshift (g_26, g_26);
    unsigned l4 = g_26 - l2;
    g_78 &= (l4 && (g_26-1)) + l1;
  } 
}

static void func_2 (void)
{
  func_28 (1, 1);
}

int main(void)
{
  func_2();
  func_28 (-1, 1);
  printf("%d\n", g_78);
  return 0;
}