On Fri, 13 Mar 2015, Thomas Preud'homme wrote:
> Hi,
>
> The description is longer than the patch so you might want to skip directly
> to it.
>
> The dot file generated by -fdump-rtl-*-graph switches group basic blocks for
> a given function together in a subgraph and use the function name as the
> label. However, when generating an image (for instance a svg with "dot
> -Tsvg") the label does not appear. This makes analyzing the resulting file
> more difficult than it should be.
>
> The section "Subgraphs and clusters" of "The DOT language" document contains
> the following excerpt:
>
> "The third role for subgraphs directly involves how the graph will be laid
> out by certain layout engines. If the name of the subgraph begins with
> cluster, Graphviz notes the subgraph as a special cluster subgraph. If
> supported, the layout engine will do the layout so that the nodes belonging
> to the cluster are drawn together, with the entire drawing of the cluster
> contained within a bounding rectangle. Note that, for good and bad, cluster
> subgraphs are not part of the DOT language, but solely a syntactic convention
> adhered to by certain of the layout engines."
>
> Hence prepending cluster_ to subgraph id (not its label) would improve the
> output image with many layout engines while no doing any difference for other
> layout engines. The patch also make the subgraph boudary visible with dashed
> lines and add "()" to the label of the subgraph (so for a function f the
> label would be "f ()").
>
> ChangeLog entry is as follows:
>
> *** gcc/ChangeLog ***
>
> 2015-03-10 Thomas Preud'homme <thomas.preudho...@arm.com>
>
> * graph.c (print_graph_cfg): Make function names visible and append
> parenthesis to it. Also make groups of basic blocks belonging to the
> same function visible.
>
>
> diff --git a/gcc/graph.c b/gcc/graph.c
> index a1eb24c..5fb0d78 100644
> --- a/gcc/graph.c
> +++ b/gcc/graph.c
> @@ -292,9 +292,10 @@ print_graph_cfg (const char *base, struct function *fun)
> pretty_printer graph_slim_pp;
> graph_slim_pp.buffer->stream = fp;
> pretty_printer *const pp = &graph_slim_pp;
> - pp_printf (pp, "subgraph \"%s\" {\n"
> - "\tcolor=\"black\";\n"
> - "\tlabel=\"%s\";\n",
> + pp_printf (pp, "subgraph \"cluster_%s\" {\n"
> + "\tstyle=\"dashed\";\n"
> + "\tcolor=\"black\";\n"
> + "\tlabel=\"%s ()\";\n",
> funcname, funcname);
> draw_cfg_nodes (pp, fun);
> draw_cfg_edges (pp, fun);
>
> Is this ok for stage1? It's not a bug but it helps debuggability so is
> this something we might consider backporting?
It's ok now given you bootstrapped the change.
Thanks,
Richard.
