The current gcc trunk and gcc 4.8 produce wrong code that hangs for the following testcase on x86_64-linux when compiled at -O3 (in both 32-bit and 64-bit modes). 

This is a regression from 4.7.x.

The testcase also triggers a different issue at -O2: a spurious "undefined behavior" warning (see below). 

$ 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/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --enable-languages=c,c++,objc,obj-c++,fortran,lto --disable-werror --enable-checking=release --with-gmp=/usr/local/gcc-trunk --with-mpfr=/usr/local/gcc-trunk --with-mpc=/usr/local/gcc-trunk --with-cloog=/usr/local/gcc-trunk --prefix=/usr/local/gcc-trunk
Thread model: posix
gcc version 4.9.0 20131014 (experimental) [trunk revision 203572] (GCC) 
$ 
$ gcc-trunk -O2 small.c; a.out
small.c: In function ‘main’:
cc1: warning: iteration 5u invokes undefined behavior [-Waggressive-loop-optimizations]
small.c:6:3: note: containing loop
   for (b = 4; b > -30; b--)
   ^
$ 
$ gcc-trunk -Os small.c; a.out
$
$ gcc-trunk -O3 small.c; a.out
^C
$ gcc-4.8 -O3 small.c; a.out
^C
$
$ gcc-4.7 -O3 small.c; a.out
$  


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


int a, b, c, d, e;

int
main ()
{
  for (b = 4; b > -30; b--)
    for (; c;)
      for (;;)
	{
	  e = a > 2147483647 - b;
	  if (d)
	    break;
	}
  return 0;
}