From 88fde7f728612252eef9624a40b3b3f7868309f1 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Mon, 17 Oct 2016 02:28:31 +0200
Subject: [PATCH 1/2] Don't process cycles when stalled

This improves the `inflate-0.1.0` benchmark by about 10% for me.
---
 src/librustc_data_structures/obligation_forest/mod.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/librustc_data_structures/obligation_forest/mod.rs b/src/librustc_data_structures/obligation_forest/mod.rs
index c079146edbf42..fb2d3291a601b 100644
--- 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);
 

From 0c844d23046161e831a2c265e5b733674cb89655 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Mon, 17 Oct 2016 21:53:27 +0200
Subject: [PATCH 2/2] Set stalled=false when encountering an error

---
 src/librustc_data_structures/obligation_forest/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/librustc_data_structures/obligation_forest/mod.rs b/src/librustc_data_structures/obligation_forest/mod.rs
index fb2d3291a601b..5e590cb445f79 100644
--- a/src/librustc_data_structures/obligation_forest/mod.rs
+++ b/src/librustc_data_structures/obligation_forest/mod.rs
@@ -333,6 +333,7 @@ impl<O: ForestObligation> ObligationForest<O> {
                     }
                 }
                 Err(err) => {
+                    stalled = false;
                     let backtrace = self.error_at(index);
                     errors.push(Error {
                         error: err,