add graphvis DOT files to dump mir directory

src/librustc/session/config.rs

@@ -1057,6 +1057,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "dump MIR state at various points in translation"),
     dump_mir_dir: Option<String> = (None, parse_opt_string, [UNTRACKED],
           "the directory the MIR is dumped into"),
+    dump_mir_graphviz: bool = (false, parse_bool, [UNTRACKED],
+          "additionally to `.mir` files, create graphviz `.dot` files"),
     dump_mir_exclude_pass_number: bool = (false, parse_bool, [UNTRACKED],
           "if set, exclude the pass number when dumping MIR (used in tests)"),
     mir_emit_validate: usize = (0, parse_uint, [TRACKED],
@@ -2650,6 +2652,8 @@ mod tests {
         assert_eq!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
         opts.debugging_opts.dump_mir_dir = Some(String::from("abc"));
         assert_eq!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
+        opts.debugging_opts.dump_mir_graphviz = true;
+        assert_eq!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
 
         // Make sure changing a [TRACKED] option changes the hash
         opts = reference.clone();

src/librustc_mir/util/graphviz.rs

@@ -30,31 +30,40 @@ pub fn write_mir_graphviz<'a, 'tcx, W>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     for def_id in dump_mir_def_ids(tcx, single) {
         let nodeid = tcx.hir.as_local_node_id(def_id).unwrap();
         let mir = &tcx.optimized_mir(def_id);
-
-        writeln!(w, "digraph Mir_{} {{", nodeid)?;
-
-        // Global graph properties
-        writeln!(w, r#"    graph [fontname="monospace"];"#)?;
-        writeln!(w, r#"    node [fontname="monospace"];"#)?;
-        writeln!(w, r#"    edge [fontname="monospace"];"#)?;
-
-        // Graph label
-        write_graph_label(tcx, nodeid, mir, w)?;
-
-        // Nodes
-        for (block, _) in mir.basic_blocks().iter_enumerated() {
-            write_node(block, mir, w)?;
-        }
-
-        // Edges
-        for (source, _) in mir.basic_blocks().iter_enumerated() {
-            write_edges(source, mir, w)?;
-        }
-        writeln!(w, "}}")?
+        write_mir_fn_graphviz(tcx, nodeid, mir, w)?;
     }
     Ok(())
 }
 
+/// Write a graphviz DOT graph of the MIR.
+pub fn write_mir_fn_graphviz<'a, 'tcx, W>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                        nodeid: NodeId,
+                                        mir: &Mir,
+                                        w: &mut W) -> io::Result<()>
+    where W: Write
+{
+    writeln!(w, "digraph Mir_{} {{", nodeid)?;
+
+    // Global graph properties
+    writeln!(w, r#"    graph [fontname="monospace"];"#)?;
+    writeln!(w, r#"    node [fontname="monospace"];"#)?;
+    writeln!(w, r#"    edge [fontname="monospace"];"#)?;
+
+    // Graph label
+    write_graph_label(tcx, nodeid, mir, w)?;
+
+    // Nodes
+    for (block, _) in mir.basic_blocks().iter_enumerated() {
+        write_node(block, mir, w)?;
+    }
+
+    // Edges
+    for (source, _) in mir.basic_blocks().iter_enumerated() {
+        write_edges(source, mir, w)?;
+    }
+    writeln!(w, "}}")
+}
+
 /// Write a graphviz HTML-styled label for the given basic block, with
 /// all necessary escaping already performed. (This is suitable for
 /// emitting directly, as is done in this module, or for use with the

src/librustc_mir/util/pretty.rs

@@ -20,6 +20,7 @@ use std::fmt::Display;
 use std::fs;
 use std::io::{self, Write};
 use std::path::{PathBuf, Path};
+use super::graphviz::write_mir_fn_graphviz;
 
 const INDENT: &'static str = "    ";
 /// Alignment for lining up comments following MIR statements
@@ -128,6 +129,14 @@ fn dump_matched_mir_node<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         write_mir_fn(tcx, source, mir, &mut file)?;
         Ok(())
     });
+
+    if tcx.sess.opts.debugging_opts.dump_mir_graphviz {
+        file_path.set_extension("dot");
+        let _ = fs::File::create(&file_path).and_then(|mut file| {
+            write_mir_fn_graphviz(tcx, source.item_id(), mir, &mut file)?;
+            Ok(())
+        });
+    }
 }
 
 /// Write out a human-readable textual representation for the given MIR.