Don't process cycles when stalled

jonas-schievink · jonas-schievink · commit 88fde7f72861 · 2016-10-17T02:28:31.000+02:00
This improves the `inflate-0.1.0` benchmark by about 10% for me.
diff --git a/src/librustc_data_structures/obligation_forest/mod.rs b/src/librustc_data_structures/obligation_forest/mod.rs
@@ -342,6 +342,16 @@ impl<O: ForestObligation> ObligationForest<O> {
             }
         }
 
+        if stalled {
+            // There's no need to perform marking, cycle processing and compression when nothing
+            // changed.
+            return Outcome {
+                completed: vec![],
+                errors: errors,
+                stalled: stalled,
+            };
+        }
+
         self.mark_as_waiting();
         self.process_cycles(processor);
 
