Inline and remove iterate_until_fixed_point().

The commit also removes the debug statement, because they annoyed me.
This change wins another 1% on `unicode_normalization`, at least partly
because it no longer needs to increment `iteration`.

Author: nnethercote

src/librustc/infer/lexical_region_resolve/mod.rs

@@ -304,8 +304,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
     }
 
     fn expansion(&self, var_values: &mut LexicalRegionResolutions<'tcx>) {
-        self.iterate_until_fixed_point(|constraint| {
-            debug!("expansion: constraint={:?}", constraint);
+        let mut process_constraint = |constraint: &Constraint<'tcx>| {
             let (a_region, b_vid, b_data, retain) = match *constraint {
                 Constraint::RegSubVar(a_region, b_vid) => {
                     let b_data = var_values.value_mut(b_vid);
@@ -331,7 +330,33 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
 
             let changed = self.expand_node(a_region, b_vid, b_data);
             (changed, retain)
-        })
+        };
+
+        // Using bitsets to track the remaining elements is faster than using a
+        // `Vec` by itself (which requires removing elements, which requires
+        // element shuffling, which is slow).
+        let constraints: Vec<_> = self.data.constraints.keys().collect();
+        let mut live_indices: BitSet<usize> = BitSet::new_filled(constraints.len());
+        let mut killed_indices: BitSet<usize> = BitSet::new_empty(constraints.len());
+        let mut changed = true;
+        while changed {
+            changed = false;
+            for index in live_indices.iter() {
+                let constraint = constraints[index];
+                let (edge_changed, retain) = process_constraint(constraint);
+                if edge_changed {
+                    changed = true;
+                }
+                if !retain {
+                    let changed = killed_indices.insert(index);
+                    debug_assert!(changed);
+                }
+            }
+            live_indices.subtract(&killed_indices);
+
+            // We could clear `killed_indices` here, but we don't need to and
+            // it's cheaper not to.
+        }
     }
 
     // This function is very hot in some workloads. There's a single callsite
@@ -866,42 +891,6 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         }
     }
 
-    fn iterate_until_fixed_point<F>(&self, mut body: F)
-    where
-        F: FnMut(&Constraint<'tcx>) -> (bool, bool),
-    {
-        // Using bitsets to track the remaining elements is faster than using a
-        // `Vec` by itself (which requires removing elements, which requires
-        // element shuffling, which is slow).
-        let constraints: Vec<_> = self.data.constraints.keys().collect();
-        let mut live_indices: BitSet<usize> = BitSet::new_filled(constraints.len());
-        let mut killed_indices: BitSet<usize> = BitSet::new_empty(constraints.len());
-        let mut iteration = 0;
-        let mut changed = true;
-        while changed {
-            changed = false;
-            iteration += 1;
-            debug!("---- Expansion iteration {}", iteration);
-            for index in live_indices.iter() {
-                let constraint = constraints[index];
-                let (edge_changed, retain) = body(constraint);
-                if edge_changed {
-                    debug!("updated due to constraint {:?}", constraint);
-                    changed = true;
-                }
-                if !retain {
-                    let changed = killed_indices.insert(index);
-                    debug_assert!(changed);
-                }
-            }
-            live_indices.subtract(&killed_indices);
-
-            // We could clear `killed_indices` here, but we don't need to and
-            // it's cheaper not to.
-        }
-        debug!("---- Expansion complete after {} iteration(s)", iteration);
-    }
-
     fn bound_is_met(
         &self,
         bound: &VerifyBound<'tcx>,