[Bug target/51106] [4.5/4.6 Regression] ICE in move_insn, at haifa-sched.c:2314

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51106

--- Comment #17 from rguenther at suse dot de <rguenther at suse dot de> 2012-03-27 13:50:57 UTC ---
On Tue, 27 Mar 2012, abel at gcc dot gnu.org wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51106
> 
> --- Comment #16 from Andrey Belevantsev <abel at gcc dot gnu.org> 2012-03-27 13:28:03 UTC ---
> So, something like the below patch, or even better -- as we want to fold all
> RTL-build related pseudo passes into expand, make pass_instantiate_virtual_regs
> also the expand part (thus, until the into_cfglayout pass), and then the new
> cleanup_cfg will nicely work at the end of expand. 
> 
> diff --git a/gcc/cfgrtl.c b/gcc/cfgrtl.c
> index b86cc74..0c27d11 100644
> --- a/gcc/cfgrtl.c
> +++ b/gcc/cfgrtl.c
> @@ -2261,7 +2261,7 @@ purge_dead_edges (basic_block bb)
>    edge e;
>    rtx insn = BB_END (bb), note;
>    bool purged = false;
> -  bool found;
> +  bool found, fallthru;
>    edge_iterator ei;
> 
>    if (DEBUG_INSN_P (insn) && insn != BB_HEAD (bb))
> @@ -2433,16 +2433,22 @@ purge_dead_edges (basic_block bb)
>       as these are only created by conditional branches.  If we find such an
>       edge we know that there used to be a jump here and can then safely
>       remove all non-fallthru edges.  */
> -  found = false;
> +  found = fallthru = false;
>    FOR_EACH_EDGE (e, ei, bb->succs)
> -    if (! (e->flags & (EDGE_COMPLEX | EDGE_FALLTHRU)))
> -      {
> +    {
> +      if (! (e->flags & (EDGE_COMPLEX | EDGE_FALLTHRU)))
>         found = true;
> -       break;
> -      }
> -
> +      if (e->flags & (EDGE_FALLTHRU | EDGE_FAKE))
> +       fallthru = true;
> +    }
>    if (!found)
>      return purged;
> +  if (!fallthru)
> +    {
> +      gcc_assert (single_succ_p (bb));
> +      single_succ_edge (bb)->flags |= EDGE_FALLTHRU;
> +      return purged;
> +    }
> 
>    /* Remove all but the fake and fallthru edges.  The fake edge may be
>       the only successor for this block in the case of noreturn
> 

Looks reasonable.  Though I think that whoever removed the fallthru
edge should have adjusted the flags on the others.