http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54146
--- Comment #35 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-08-08
11:49:21 UTC ---
(In reply to comment #34)
> (In reply to comment #33)
> > I think you should simply move compute_global_livein to its single use
> > and make it static.
>
> Yes, and I need to add the same smarts there as in find_uses_to_rename_use to
> look through loops at the same nesting level, because this test case fails:
>
> extern unsigned use (unsigned);
> void foo (void)
> {
> unsigned i, j;
> do { i = use (0); } while (i);
> do { j = use (0); } while (j);
> if (i) use (j);
> }
>
> It fails in check_loop_closed_ssa_use at -O2 but passes at -O2 -fno-tree-vrp,
> so VRP is doing something destroying the initially correct loop-closed SSA
> form.
Jump threading I suppose. I think you can drop loop-closed SSA form
right before calling vrp_finalize ().
