[PATCH] Fix PR54650

[Richard Guenther]

On Sat, Sep 22, 2012 at 4:08 AM, Dehao Chen <dehao@google.com> wrote:
> Hi,
>
> The problem is due to a bug when move_block_to_fn. edge->goto_block
> should be updated even when its locus is unknown. This patch also
> fixes the way to reset block for expr.

I think the machinery is much more fragile (which is probably why
when in SSA form the whole thing is invoked with a NULL_TREE BLOCK).
>From looking at how the block tree is mangled:

  /* Rewire BLOCK_SUBBLOCKS of orig_block.  */
  if (orig_block)
    {
      tree block;
      gcc_assert (BLOCK_SUBBLOCKS (DECL_INITIAL (dest_cfun->decl))
                  == NULL_TREE);
      BLOCK_SUBBLOCKS (DECL_INITIAL (dest_cfun->decl))
        = BLOCK_SUBBLOCKS (orig_block);
      for (block = BLOCK_SUBBLOCKS (orig_block);
           block; block = BLOCK_CHAIN (block))
        BLOCK_SUPERCONTEXT (block) = DECL_INITIAL (dest_cfun->decl);
      BLOCK_SUBBLOCKS (orig_block) = NULL_TREE;
    }

I think we want a simpler version of your fix:

> Bootstrapped and pass all gcc regression tests.
>
> Is it okay for trunk?
>
> Thanks,
> Dehao
>
> gcc/ChangeLog:
>         tree-cfg.c (move_stmt_op): Reset the expr block only
>         when necessary.
>         (move_block_to_fn): Reset the edge's goto block even
>         when the goto locus is unknown.
>
> Index: tree-cfg.c
> ===================================================================
> --- tree-cfg.c  (revision 191614)
> +++ tree-cfg.c  (working copy)
> @@ -6013,7 +6013,9 @@ move_stmt_op (tree *tp, int *walk_subtrees, void *
>
>    if (EXPR_P (t))
>      {
> -      if (TREE_BLOCK (t))
> +      if (p->orig_block == NULL_TREE
> +         || TREE_BLOCK (t) == p->orig_block
> +         || TREE_BLOCK (t) == NULL_TREE)
>         TREE_SET_BLOCK (t, p->new_block);

Only replace TREE_BLOCK of t if it was equal to p->orig_block or if
p->orig_block is NULL_TREE _and_ TREE_BLOCK of t is not NULL_TREE.

>      }
>    else if (DECL_P (t) || TREE_CODE (t) == SSA_NAME)
> @@ -6315,7 +6317,7 @@ move_block_to_fn (struct function *dest_cfun, basi
>      }
>
>    FOR_EACH_EDGE (e, ei, bb->succs)
> -    if (!IS_UNKNOWN_LOCATION (e->goto_locus))
> +    if (e->goto_locus)

Please compare against UNKNOWN_LOCATION (which is zero, right)?

Ok with that changes.

Thanks,
Richard.

>        {
>         tree block = LOCATION_BLOCK (e->goto_locus);
>         if (d->orig_block == NULL_TREE