Re: [PATCH] Fix loop unrolling ICE (PR middle-end/39124)

[Richard Guenther <richard dot guenther at gmail dot com>]

On Tue, Feb 10, 2009 at 4:33 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> During peeling if remove_path is called on a path completely containing some
> other loop GCC ICEs in get_loop_body called from cancel_loop.  The problem
> is that remove_path first calls remove_bbs on all bbs we want to remove and
> only afterwards cancel_loop_tree to remove those loops.  cancel_loop
> does:
>  /* Move blocks up one level (they should be removed as soon as possible).  */
>  bbs = get_loop_body (loop);
>  for (i = 0; i < loop->num_nodes; i++)
>    bbs[i]->loop_father = outer;
> but get_loop_body ICEs when loop->num_nodes == 0 (as all the bbs have been
> removed previously).  The following patch just swaps the order, first
> cancels loops and only afterwards removes the bbs, which I think matches the
> above mentioned comment and also matches what tree-loop-distribution.c
> does:
>      cancel_loop_tree (loop);
>
>      for (i = 0; i < nbbs; i++)
>        delete_basic_block (bbs[i]);
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2009-02-10  Jakub Jelinek  <jakub@redhat.com>
>
>        PR middle-end/39124
>        * cfgloopmanip.c (remove_path): Call remove_bbs after
>        cancel_loop_tree, not before it.
>
> --- gcc/cfgloopmanip.c.jj       2008-10-23 13:21:39.000000000 +0200
> +++ gcc/cfgloopmanip.c  2009-02-10 14:55:04.000000000 +0100
> @@ -1,5 +1,5 @@
>  /* Loop manipulation code for GNU compiler.
> -   Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008 Free Software
> +   Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008, 2009 Free Software
>    Foundation, Inc.
>
>  This file is part of GCC.
> @@ -349,13 +349,13 @@ remove_path (edge e)
>     if (rem_bbs[i]->loop_father->header == rem_bbs[i])
>       deleted_loop[nreml++] = rem_bbs[i]->loop_father;
>
> -  remove_bbs (rem_bbs, nrem);
> -  free (rem_bbs);
> -
>   for (i = 0; i < nreml; i++)
>     cancel_loop_tree (deleted_loop[i]);
>   free (deleted_loop);
>
> +  remove_bbs (rem_bbs, nrem);
> +  free (rem_bbs);
> +
>   /* Find blocks whose dominators may be affected.  */
>   sbitmap_zero (seen);
>   for (i = 0; i < n_bord_bbs; i++)
>
>        Jakub
>