[Bug tree-optimization/48739] [4.5/4.6/4.7 Regression] ICE in check_loop_closed_ssa_use() with "-ftree-parallelize-loops=2 -fno-tree-dominator-opts"

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48739

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
   Target Milestone|---                         |4.5.4
            Summary|ICE in                      |[4.5/4.6/4.7 Regression]
                   |check_loop_closed_ssa_use() |ICE in
                   |with                        |check_loop_closed_ssa_use()
                   |"-ftree-parallelize-loops=2 |with
                   |-fno-tree-dominator-opts"   |"-ftree-parallelize-loops=2
                   |                            |-fno-tree-dominator-opts"

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-08-19 16:38:45 UTC ---
Simplified testcase:

/* PR tree-optimization/48739 */
/* { dg-do compile } */
/* { dg-options "-O1 -ftree-parallelize-loops=2 -fno-tree-dominator-opts" } */

extern int g;
extern void bar (void);

int
foo (int x)
{
  int a, b, *c = (int *) 0;
  for (a = 0; a < 10; ++a)
    {
      bar ();
      for (b = 0; b < 5; ++b)
        {
          x = 0;
          c = &x;
          g = 1;
        }
    }
  *c = x;
  for (x = 0; x != 10; x++)
    ;
  return g;
}

Started with http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=149206
(before that the empty loop would be just removed).

The bug seems to be that parloops pass requests TODO_rebuild_alias which
changes x from TREE_ADDRESSABLE to a gimple var, but we are in loop closed SSA
form at that point and nothing ensures that the optimized variable is put into
loop closed SSA form.