dump scc graphviz too

src/librustc_data_structures/graph/scc/mod.rs

@@ -54,6 +54,11 @@ impl<N: Idx, S: Idx> Sccs<N, S> {
         self.scc_data.len()
     }
 
+    /// Returns the number of SCCs in the graph.
+    pub fn all_sccs(&self) -> impl Iterator<Item = S> {
+        (0 .. self.scc_data.len()).map(S::new)
+    }
+
     /// Returns the SCC to which a node `r` belongs.
     pub fn scc(&self, r: N) -> S {
         self.scc_indices[r]

src/librustc_mir/borrow_check/nll/mod.rs

@@ -295,9 +295,16 @@ fn dump_mir_results<'a, 'gcx, 'tcx>(
     // Also dump the inference graph constraints as a graphviz file.
     let _: io::Result<()> = do catch {
         let mut file =
-            pretty::create_dump_file(infcx.tcx, "regioncx.dot", None, "nll", &0, source)?;
+            pretty::create_dump_file(infcx.tcx, "regioncx.all.dot", None, "nll", &0, source)?;
         regioncx.dump_graphviz_raw_constraints(&mut file)?;
     };
+
+    // Also dump the inference graph constraints as a graphviz file.
+    let _: io::Result<()> = do catch {
+        let mut file =
+            pretty::create_dump_file(infcx.tcx, "regioncx.scc.dot", None, "nll", &0, source)?;
+        regioncx.dump_graphviz_scc_constraints(&mut file)?;
+    };
 }
 
 fn dump_annotation<'a, 'gcx, 'tcx>(

src/librustc_mir/borrow_check/nll/region_infer/graphviz.rs

@@ -12,22 +12,37 @@
 //! libgraphviz traits, specialized to attaching borrowck analysis
 //! data to rendered labels.
 
+use super::*;
+use borrow_check::nll::constraints::OutlivesConstraint;
 use dot::{self, IntoCow};
 use rustc_data_structures::indexed_vec::Idx;
 use std::borrow::Cow;
 use std::io::{self, Write};
-use super::*;
-use borrow_check::nll::constraints::OutlivesConstraint;
 
 impl<'tcx> RegionInferenceContext<'tcx> {
     /// Write out the region constraint graph.
-    pub(crate) fn dump_graphviz_raw_constraints(&self, mut w: &mut dyn Write) -> io::Result<()> {
+    crate fn dump_graphviz_raw_constraints(&self, mut w: &mut dyn Write) -> io::Result<()> {
         dot::render(&RawConstraints { regioncx: self }, &mut w)
     }
+
+    /// Write out the region constraint graph.
+    crate fn dump_graphviz_scc_constraints(&self, mut w: &mut dyn Write) -> io::Result<()> {
+        let mut nodes_per_scc: IndexVec<ConstraintSccIndex, _> = self.constraints_scc
+            .all_sccs()
+            .map(|_| Vec::new())
+            .collect();
+
+        for region in self.definitions.indices() {
+            let scc = self.constraints_scc.scc(region);
+            nodes_per_scc[scc].push(region);
+        }
+
+        dot::render(&SccConstraints { regioncx: self, nodes_per_scc }, &mut w)
+    }
 }
 
 struct RawConstraints<'a, 'tcx: 'a> {
-    regioncx: &'a RegionInferenceContext<'tcx>
+    regioncx: &'a RegionInferenceContext<'tcx>,
 }
 
 impl<'a, 'this, 'tcx> dot::Labeller<'this> for RawConstraints<'a, 'tcx> {
@@ -63,14 +78,74 @@ impl<'a, 'this, 'tcx> dot::GraphWalk<'this> for RawConstraints<'a, 'tcx> {
         (&self.regioncx.constraints.raw[..]).into_cow()
     }
 
-    // Render `a: b` as `a <- b`, indicating the flow
+    // Render `a: b` as `a -> b`, indicating the flow
     // of data during inference.
 
     fn source(&'this self, edge: &OutlivesConstraint) -> RegionVid {
-        edge.sub
+        edge.sup
     }
 
     fn target(&'this self, edge: &OutlivesConstraint) -> RegionVid {
-        edge.sup
+        edge.sub
+    }
+}
+
+struct SccConstraints<'a, 'tcx: 'a> {
+    regioncx: &'a RegionInferenceContext<'tcx>,
+    nodes_per_scc: IndexVec<ConstraintSccIndex, Vec<RegionVid>>,
+}
+
+impl<'a, 'this, 'tcx> dot::Labeller<'this> for SccConstraints<'a, 'tcx> {
+    type Node = ConstraintSccIndex;
+    type Edge = (ConstraintSccIndex, ConstraintSccIndex);
+
+    fn graph_id(&'this self) -> dot::Id<'this> {
+        dot::Id::new(format!("RegionInferenceContext")).unwrap()
+    }
+    fn node_id(&'this self, n: &ConstraintSccIndex) -> dot::Id<'this> {
+        dot::Id::new(format!("r{}", n.index())).unwrap()
+    }
+    fn node_shape(&'this self, _node: &ConstraintSccIndex) -> Option<dot::LabelText<'this>> {
+        Some(dot::LabelText::LabelStr(Cow::Borrowed("box")))
+    }
+    fn node_label(&'this self, n: &ConstraintSccIndex) -> dot::LabelText<'this> {
+        let nodes = &self.nodes_per_scc[*n];
+        dot::LabelText::LabelStr(format!("{:?} = {:?}", n, nodes).into_cow())
+    }
+}
+
+impl<'a, 'this, 'tcx> dot::GraphWalk<'this> for SccConstraints<'a, 'tcx> {
+    type Node = ConstraintSccIndex;
+    type Edge = (ConstraintSccIndex, ConstraintSccIndex);
+
+    fn nodes(&'this self) -> dot::Nodes<'this, ConstraintSccIndex> {
+        let vids: Vec<ConstraintSccIndex> = self.regioncx.constraints_scc.all_sccs().collect();
+        vids.into_cow()
+    }
+    fn edges(&'this self) -> dot::Edges<'this, (ConstraintSccIndex, ConstraintSccIndex)> {
+        let edges: Vec<_> = self.regioncx
+            .constraints_scc
+            .all_sccs()
+            .flat_map(|scc_a| {
+                self.regioncx
+                    .constraints_scc
+                    .successors(scc_a)
+                    .iter()
+                    .map(move |&scc_b| (scc_a, scc_b))
+            })
+            .collect();
+
+        edges.into_cow()
+    }
+
+    // Render `a: b` as `a -> b`, indicating the flow
+    // of data during inference.
+
+    fn source(&'this self, edge: &(ConstraintSccIndex, ConstraintSccIndex)) -> ConstraintSccIndex {
+        edge.0
+    }
+
+    fn target(&'this self, edge: &(ConstraintSccIndex, ConstraintSccIndex)) -> ConstraintSccIndex {
+        edge.1
     }
 }

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -9,8 +9,9 @@
 // except according to those terms.
 
 use super::universal_regions::UniversalRegions;
-use borrow_check::nll::constraints::{ConstraintIndex, ConstraintSccIndex, ConstraintSet,
-                                     OutlivesConstraint};
+use borrow_check::nll::constraints::{
+    ConstraintIndex, ConstraintSccIndex, ConstraintSet, OutlivesConstraint,
+};
 use borrow_check::nll::region_infer::values::ToElementIndex;
 use borrow_check::nll::type_check::Locations;
 use rustc::hir::def_id::DefId;
@@ -26,7 +27,8 @@ use rustc::mir::{
 use rustc::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable};
 use rustc::util::common;
 use rustc_data_structures::graph::scc::Sccs;
-use rustc_data_structures::indexed_vec::{Idx, IndexVec};
+use rustc_data_structures::indexed_set::{IdxSet, IdxSetBuf};
+use rustc_data_structures::indexed_vec::IndexVec;
 
 use std::rc::Rc;
 
@@ -402,14 +404,28 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // SCC. For each SCC, we visit its successors and compute
         // their values, then we union all those values to get our
         // own.
-        for scc_index in (0..self.constraints_scc.num_sccs()).map(ConstraintSccIndex::new) {
-            self.propagate_constraints_scc(scc_index);
+        let visited = &mut IdxSetBuf::new_empty(self.constraints_scc.num_sccs());
+        for scc_index in self.constraints_scc.all_sccs() {
+            self.propagate_constraints_scc_if_new(scc_index, visited);
         }
     }
 
-    fn propagate_constraints_scc(&mut self, scc_a: ConstraintSccIndex) {
-        debug!("propagate_constraints_scc(scc_a = {:?})", scc_a);
+    #[inline]
+    fn propagate_constraints_scc_if_new(
+        &mut self,
+        scc_a: ConstraintSccIndex,
+        visited: &mut IdxSet<ConstraintSccIndex>,
+    ) {
+        if visited.add(&scc_a) {
+            self.propagate_constraints_scc_new(scc_a, visited);
+        }
+    }
 
+    fn propagate_constraints_scc_new(
+        &mut self,
+        scc_a: ConstraintSccIndex,
+        visited: &mut IdxSet<ConstraintSccIndex>,
+    ) {
         let constraints_scc = self.constraints_scc.clone();
 
         // Walk each SCC `B` such that `A: B`...
@@ -420,7 +436,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             );
 
             // ...compute the value of `B`...
-            self.propagate_constraints_scc(scc_b);
+            self.propagate_constraints_scc_if_new(scc_b, visited);
 
             // ...and add elements from `B` into `A`.
             self.scc_values.add_region(scc_a, scc_b);