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

This is a regression from 5.2.x.

I wasn't able to get rid of the call to printf. 


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-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 6.0.0 20150930 (experimental) [trunk revision 228291] (GCC) 
$ 
$ gcc-trunk -O2 small.c; ./a.out
 $ 
$ gcc-5.2 -O3 small.c; ./a.out
 $ 
$ 
$ gcc-trunk -O3 small.c
$ ./a.out
 Aborted
$ 


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


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

int a, c, f, g;
char b;

static int
fn1 ()
{
  char h;
  int k = -1, i, j;
  for (; b < 16; b++)
    ;
  printf (" ");
  if (b < 5)
    k++;
  if (k)
    {
      int l = 2;
      a = h = b < 0 || b > (127 >> l) ? b : b << 1;
      return 0;
    }
  for (i = 0; i < 1; i++)
    for (j = 0; j < 7; j++)
      f = 0;
  for (c = 0; c; c++)
    ;
  if (g)
    for (;;)
      ;
  return 0;
}

int
main ()
{
  fn1 ();
  
  if (a != 32) 
    __builtin_abort (); 

  return 0;
}