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?
Best regards,
Thomas
