[was: Re: [PATCH] Add dotfn ]
On 07/03/2017 12:23 PM, Richard Biener wrote:
Btw, I think this needs fixing:
...
/* Draw all edges in the CFG. Retreating edges are drawin as not
constraining, this makes the layout of the graph better.
(??? Calling mark_dfs_back may change the compiler's behavior when
dumping, but computing back edges here for ourselves is also not
desirable.) */
static void
draw_cfg_edges (pretty_printer *pp, struct function *fun)
{
basic_block bb;
mark_dfs_back_edges ();
FOR_ALL_BB_FN (bb, cfun)
draw_cfg_node_succ_edges (pp, fun->funcdef_no, bb);
...
We don't want that calling a debug function changes compiler behavior
(something I ran into while debugging PR81192).
Any suggestion on how to address this? We could allocate a bitmap before and
save the edge flag for all edges, and restore afterwards.
Something like that, yes.
This patch implements that approach.
I've tried it with the PR81192 example and calling DOTFN in tail-merge,
like this:
1. Just compiling the example without any patches gives a tail-merge
sigsegv.
2. Compiling with the DOTFN call in tail-merge makes the sigsegv go
away.
3. Adding this patch makes the sigsegv come back.
OK for trunk if bootstrap and reg-test on x86_64 succeeds?
Thanks,
- Tom
Save and restore EDGE_DFS_BACK in draw_cfg_edges
2017-07-03 Tom de Vries <t...@codesourcery.com>
* graph.c (draw_cfg_edges): Save and restore EDGE_DFS_BACK.
---
gcc/graph.c | 49 +++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 45 insertions(+), 4 deletions(-)
diff --git a/gcc/graph.c b/gcc/graph.c
index 9261732..628769b 100644
--- a/gcc/graph.c
+++ b/gcc/graph.c
@@ -243,19 +243,60 @@ draw_cfg_nodes (pretty_printer *pp, struct function *fun)
}
/* Draw all edges in the CFG. Retreating edges are drawin as not
- constraining, this makes the layout of the graph better.
- (??? Calling mark_dfs_back may change the compiler's behavior when
- dumping, but computing back edges here for ourselves is also not
- desirable.) */
+ constraining, this makes the layout of the graph better. */
static void
draw_cfg_edges (pretty_printer *pp, struct function *fun)
{
basic_block bb;
+
+ /* Save EDGE_DFS_BACK flag to dfs_back. */
+ auto_bitmap dfs_back;
+ edge e;
+ edge_iterator ei;
+ unsigned int idx = 0;
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ if (e->flags & EDGE_DFS_BACK)
+ bitmap_set_bit (dfs_back, idx);
+ idx++;
+ }
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ if (e->flags & EDGE_DFS_BACK)
+ bitmap_set_bit (dfs_back, idx);
+ idx++;
+ }
+ }
+
mark_dfs_back_edges ();
FOR_ALL_BB_FN (bb, cfun)
draw_cfg_node_succ_edges (pp, fun->funcdef_no, bb);
+ /* Restore EDGE_DFS_BACK flag from dfs_back. */
+ idx = 0;
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ if (bitmap_bit_p (dfs_back, idx))
+ e->flags |= EDGE_DFS_BACK;
+ else
+ e->flags &= ~EDGE_DFS_BACK;
+ idx++;
+ }
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ if (bitmap_bit_p (dfs_back, idx))
+ e->flags |= EDGE_DFS_BACK;
+ else
+ e->flags &= ~EDGE_DFS_BACK;
+ idx++;
+ }
+ }
+
/* Add an invisible edge from ENTRY to EXIT, to improve the graph layout. */
pp_printf (pp,
"\tfn_%d_basic_block_%d:s -> fn_%d_basic_block_%d:n "
