The following code causes an ICE when compiled with the current gcc trunk at -O1 and above on x86_64-linux-gnu in both 32-bit and 64-bit modes.

It 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 20140518 (experimental) [trunk revision 210581] (GCC) 
$ 
$ gcc-trunk -O0 -c small.c
$ gcc-4.9.0 -O1 -c small.c
$ 
$ gcc-trunk -O1 -c small.c
small.c: In function ‘bar’:
small.c:30:1: internal compiler error: Segmentation fault
 }
 ^
0x988c1f crash_signal
	../../gcc-trunk/gcc/toplev.c:337
0xa5b6de gimple_code
	../../gcc-trunk/gcc/gimple.h:1405
0xa5b6de gimple_nop_p
	../../gcc-trunk/gcc/gimple.h:5559
0xa5b6de walk_non_aliased_vuses(ao_ref*, tree_node*, void* (*)(ao_ref*, tree_node*, unsigned int, void*), void* (*)(ao_ref*, tree_node*, void*, bool), void*)
	../../gcc-trunk/gcc/tree-ssa-alias.c:2550
0xb02599 vn_reference_lookup(tree_node*, tree_node*, vn_lookup_kind, vn_reference_s**)
	../../gcc-trunk/gcc/tree-ssa-sccvn.c:2117
0xae040a eliminate_dom_walker::before_dom_children(basic_block_def*)
	../../gcc-trunk/gcc/tree-ssa-pre.c:4285
0xe93527 dom_walker::walk(basic_block_def*)
	../../gcc-trunk/gcc/domwalk.c:177
0xaddcad eliminate
	../../gcc-trunk/gcc/tree-ssa-pre.c:4429
0xade193 execute
	../../gcc-trunk/gcc/tree-ssa-pre.c:4852
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ 

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

void __assert_fail (void);

int **a, b, c, e, *j;
short *d, **f;

int *
foo ()
{
  *a = j;
  if (!(1 & e)) 
    __assert_fail ();
  return 0;
}

void
bar ()
{
  int *g = &b;
  short **h = &d;
  if ((f = &d) != h)
    for (; b;)
      {
	int i = 1;
	if (i)
	  g = foo ();
	c = 0;
      }
  if (!g)
    __assert_fail ();
}