[Bug tree-optimization/58018] New: ICE in tree_ssa_unswitch_loops at -O3

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58018

            Bug ID: 58018
           Summary: ICE in tree_ssa_unswitch_loops at -O3
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The following code causes an ICE when compiled with the current gcc trunk at
-O3 on x86_64-linux in both 32-bit and 64-bit modes. This is a regression from
4.8.x.

$ gcc-trunk -v
gcc version 4.9.0 20130728 (experimental) [trunk revision 201291] (GCC) 
$ gcc-trunk -O2 -c small.c
$ gcc-4.8 -O3 -c small.c
$ gcc-trunk -O3 -c small.c
small.c: In function ‘foo’:
small.c:9:6: internal compiler error: Segmentation fault
 void foo ()
      ^
0x7d4c4f crash_signal
    ../../gcc-trunk/gcc/toplev.c:334
0x7fccdb ssa_default_def(function*, tree_node*)
    ../../gcc-trunk/gcc/tree-dfa.c:314
0x7fcfa0 get_or_create_ssa_default_def(function*, tree_node*)
    ../../gcc-trunk/gcc/tree-dfa.c:362
0x81623a get_reaching_def
    ../../gcc-trunk/gcc/tree-into-ssa.c:1184
0x81c39a maybe_replace_use
    ../../gcc-trunk/gcc/tree-into-ssa.c:1784
0x81c39a rewrite_update_stmt
    ../../gcc-trunk/gcc/tree-into-ssa.c:1967
0x81c39a rewrite_update_enter_block
    ../../gcc-trunk/gcc/tree-into-ssa.c:2136
0xb3670a walk_dominator_tree(dom_walk_data*, basic_block_def*)
    ../../gcc-trunk/gcc/domwalk.c:210
0x814f43 rewrite_blocks
    ../../gcc-trunk/gcc/tree-into-ssa.c:2216
0x81b64e update_ssa(unsigned int)
    ../../gcc-trunk/gcc/tree-into-ssa.c:3303
0xb9da0a tree_unswitch_single_loop
    ../../gcc-trunk/gcc/tree-ssa-loop-unswitch.c:358
0xb9dff8 tree_ssa_unswitch_loops()
    ../../gcc-trunk/gcc/tree-ssa-loop-unswitch.c:116
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.
$


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


int a, b, c, d, e;

void bar (int p)
{
  int f = b;
  e &= p <= (f ^= 0);
}

void foo ()
{
  for (; d; d++)
    {
      bar (a && c);
      bar (0);
      bar (1);
    }
}