Use DefId to create globally unique basic block labels

Author: ecstatic-morse

src/librustc_mir/util/graphviz.rs

@@ -55,12 +55,12 @@ where
 
     // Nodes
     for (block, _) in body.basic_blocks().iter_enumerated() {
-        write_node(block, body, w)?;
+        write_node(def_id, block, body, w)?;
     }
 
     // Edges
     for (source, _) in body.basic_blocks().iter_enumerated() {
-        write_edges(source, body, w)?;
+        write_edges(def_id, source, body, w)?;
     }
     writeln!(w, "}}")
 }
@@ -115,21 +115,33 @@ pub fn write_node_label<W: Write, INIT, FINI>(block: BasicBlock,
 }
 
 /// Write a graphviz DOT node for the given basic block.
-fn write_node<W: Write>(block: BasicBlock, body: &Body<'_>, w: &mut W) -> io::Result<()> {
+fn write_node<W: Write>(
+    def_id: DefId,
+    block: BasicBlock,
+    body: &Body<'_>,
+    w: &mut W,
+) -> io::Result<()> {
     // Start a new node with the label to follow, in one of DOT's pseudo-HTML tables.
-    write!(w, r#"    {} [shape="none", label=<"#, node(block))?;
+    write!(w, r#"    {} [shape="none", label=<"#, node(def_id, block))?;
     write_node_label(block, body, w, 1, |_| Ok(()), |_| Ok(()))?;
     // Close the node label and the node itself.
     writeln!(w, ">];")
 }
 
 /// Write graphviz DOT edges with labels between the given basic block and all of its successors.
-fn write_edges<W: Write>(source: BasicBlock, body: &Body<'_>, w: &mut W) -> io::Result<()> {
+fn write_edges<W: Write>(
+    def_id: DefId,
+    source: BasicBlock,
+    body: &Body<'_>,
+    w: &mut W,
+) -> io::Result<()> {
     let terminator = body[source].terminator();
     let labels = terminator.kind.fmt_successor_labels();
 
     for (&target, label) in terminator.successors().zip(labels) {
-        writeln!(w, r#"    {} -> {} [label="{}"];"#, node(source), node(target), label)?;
+        let src = node(def_id, source);
+        let trg = node(def_id, target);
+        writeln!(w, r#"    {} -> {} [label="{}"];"#, src, trg, label)?;
     }
 
     Ok(())
@@ -181,8 +193,8 @@ fn write_graph_label<'tcx, W: Write>(
     writeln!(w, ">;")
 }
 
-fn node(block: BasicBlock) -> String {
-    format!("bb{}", block.index())
+fn node(def_id: DefId, block: BasicBlock) -> String {
+    format!("bb{}__{}", block.index(), graphviz_safe_def_name(def_id))
 }
 
 fn escape<T: Debug>(t: &T) -> String {