51813

diff --git a/src/librustc_mir/dataflow/mod.rs b/src/librustc_mir/dataflow/mod.rs
index 85458c7..eb5aace 100644
--- a/src/librustc_mir/dataflow/mod.rs
+++ b/src/librustc_mir/dataflow/mod.rs
@@ -11,7 +11,7 @@
 use syntax::ast::{self, MetaItem};
 
 use rustc_data_structures::indexed_set::{IdxSet, IdxSetBuf};
-use rustc_data_structures::indexed_vec::Idx;
+use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 use rustc_data_structures::bitslice::{bitwise, BitwiseOperator};
 
 use rustc::ty::{self, TyCtxt};
@@ -177,6 +177,7 @@ struct PropagationContext<'b, 'a: 'b, 'tcx: 'a, O> where O: 'b + BitDenotation
 {
     builder: &'b mut DataflowAnalysis<'a, 'tcx, O>,
     changed: bool,
+    first_iteration: bool,
 }
 
 impl<'a, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
@@ -186,10 +187,13 @@ impl<'a, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
         let mut propcx = PropagationContext {
             builder: self,
             changed: true,
+            first_iteration: true
         };
-        while propcx.changed {
-            propcx.changed = false;
-            propcx.walk_cfg(&mut temp);
+        let mut dirty_list: IndexVec<BasicBlock, BasicBlockData<'tcx>> = IndexVec::new();
+
+        while propcx.first_iteration == true || !dirty_list.is_empty() {
+            propcx.walk_cfg(&mut temp, &mut dirty_list);
+            propcx.first_iteration = false;
         }
     }
 
@@ -235,9 +239,21 @@ impl<'a, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
 
 impl<'b, 'a: 'b, 'tcx: 'a, BD> PropagationContext<'b, 'a, 'tcx, BD> where BD: BitDenotation
 {
-    fn walk_cfg(&mut self, in_out: &mut IdxSet<BD::Idx>) {
+    fn walk_cfg(&mut self, in_out: &mut IdxSet<BD::Idx>,
+                dirty_list: &mut IndexVec<BasicBlock, BasicBlockData<'tcx>>) {
         let mir = self.builder.mir;
-        for (bb_idx, bb_data) in mir.basic_blocks().iter().enumerate() {
+        let dirty_list_clone = &dirty_list.clone();
+        let basic_blocks : &IndexVec<BasicBlock, BasicBlockData<>>;
+        if !self.first_iteration {
+            basic_blocks = dirty_list_clone;
+        } else {
+            basic_blocks = mir.basic_blocks();
+        }
+
+        let mut new_dirty_list: IndexVec<BasicBlock, BasicBlockData<'tcx>> = IndexVec::new();
+        for (bb_idx, bb_data) in basic_blocks.iter().enumerate() {
+            info!("bb_idx is {:?}", bb_idx);
+            self.changed = false;
             let builder = &mut self.builder;
             {
                 let sets = builder.flow_state.sets.for_block(bb_idx);
@@ -248,7 +264,14 @@ impl<'b, 'a: 'b, 'tcx: 'a, BD> PropagationContext<'b, 'a, 'tcx, BD> where BD: Bi
             }
             builder.propagate_bits_into_graph_successors_of(
                 in_out, &mut self.changed, (mir::BasicBlock::new(bb_idx), bb_data));
+
+
+            if self.changed {
+                new_dirty_list.push(bb_data.clone());
+            }
+
         }
+        *dirty_list = new_dirty_list;
     }
 }