On Thu, Aug 27, 2015 at 4:33 PM, Michael Matz <m...@suse.de> wrote:
> Hello,
>
> I've this in my tree since some time already. In-tree there is only one
> user of pre_and_rev_post_order_compute{,_fn} that actually wants entry and
> exit included, and that one is just a debug routine
> (draw_cfg_nodes_no_loops); so this bug right now is harmless. But I've
> used this for some other patches, and in particular the hsa branch now
> introduces a use that's really interested in entry and exit blocks (only
> for code quality, but hey).
>
> So, to demonstrate, given such CFG:
>
> EN -> 1 -> 2 -> EX
> |--> 3 /
>
> One pre order would be:
> EN, 1, 2, 3, EX
>
> One post order would be:
> EX, 2, 3, 1, EN
>
> And therefore a reverse post order would be:
> EN, 1, 3, 2, EX
>
> In particular in a reverse post order the entry block comes first, and the
> exit block last. The routine contains a thinko in that it places the
> entry block last, and the exit block first. The bug exists since the
> introduction of the include_entry_exit parameter.
>
> I'm regstrapping with this in-tree since many moons, but just started
> another one; of course, given that there aren't non-debug users right now,
> no changes in testsuites are expected.
>
> Okay for trunk?
Ok.
Richard.
>
> Ciao,
> Michael.
> ------------------
> * cfganal.c (pre_and_rev_post_order_compute_fn): Correctly
> enter entry and exit blocks for reverse post order.
>
> Index: cfganal.c
> ===================================================================
> --- cfganal.c (revision 227259)
> +++ cfganal.c (working copy)
> @@ -925,7 +925,7 @@ pre_and_rev_post_order_compute_fn (struc
> pre_order[pre_order_num] = ENTRY_BLOCK;
> pre_order_num++;
> if (rev_post_order)
> - rev_post_order[rev_post_order_num--] = ENTRY_BLOCK;
> + rev_post_order[rev_post_order_num--] = EXIT_BLOCK;
> }
> else
> rev_post_order_num -= NUM_FIXED_BLOCKS;
> @@ -996,7 +996,7 @@ pre_and_rev_post_order_compute_fn (struc
> pre_order[pre_order_num] = EXIT_BLOCK;
> pre_order_num++;
> if (rev_post_order)
> - rev_post_order[rev_post_order_num--] = EXIT_BLOCK;
> + rev_post_order[rev_post_order_num--] = ENTRY_BLOCK;
> }
>
> return pre_order_num;
