Add images of graphs

Author: amandasystems

src/img/region-graphviz.png

@@ -219,18 +219,23 @@ the example below:
 
 ### Region Constraint Graphs and Their Strongly Connected Components
 
+![A graph showing a small number of regions with their outlives relations](../img/region-graphviz.png)
+
 With `-Z dump-mir-graphviz=yes`, you will also get Graphviz files for the outlives constraints
 of the MIR bodies you asked for, as well as the strongly connected components (SCCs) on them.
-They are available as 
+They are available as
 `mir_dump/rs-file-name.function-name.-------.nll.0.regioncx.all.dot` and
 `mir_dump/rs-file-name.function-name.-------.nll.0.regioncx.scc.dot` respectively. For both
 graphs, named region variables will be shown with their external name (such as `'static`)
 shown in parenthesis. For region inference variables in universes other than the root universe,
-they will be shown as `/U13` (for universe 13). In the region graph, edges are labelled with 
-the MIR locations where the relationship holds.
+they will be shown as `/U13` (for universe 13). In the region graph, edges are labelled with
+the MIR locations where the relationship holds, or `All` if it's everywhere.
+
+![A graph showing a small number of strongly connected components on the region-outlives-graph above](../img/scc-graphviz.png)
 
-**Note:** there are implicit edges from `'static` to every region, but those are not rendered
-in the region graph to avoid clutter. They *do* however show up in the SCC graph.
+**Note:** There are implicit edges from `'static` to every region, but those are not rendered
+in the region graph to avoid clutter. They _do_ however show up in the SCC graph. This is why there are outgoing edges from SCC(5) in the SCC graph above
+that do not seem to have corresponding edges in the region outlives graph above.
 
 ["gen-kill" problems]: https://en.wikipedia.org/wiki/Data-flow_analysis#Bit_vector_problems
 [*Static Program Analysis*]: https://cs.au.dk/~amoeller/spa/