diff --git a/clang/lib/Analysis/LiveVariables.cpp b/clang/lib/Analysis/LiveVariables.cpp
index 5e0a9a0..cd73a62e 100644
--- a/clang/lib/Analysis/LiveVariables.cpp
+++ b/clang/lib/Analysis/LiveVariables.cpp
@@ -19,6 +19,7 @@
 #include "clang/Analysis/CFG.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/PriorityQueue.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <vector>
@@ -28,20 +29,21 @@
 namespace {
 
 class DataflowWorklist {
-  SmallVector<const CFGBlock *, 20> worklist;
   llvm::BitVector enqueuedBlocks;
   PostOrderCFGView *POV;
+  llvm::PriorityQueue<const CFGBlock *, SmallVector<const CFGBlock *, 20>,
+                      PostOrderCFGView::BlockOrderCompare> worklist;
+
 public:
   DataflowWorklist(const CFG &cfg, AnalysisDeclContext &Ctx)
     : enqueuedBlocks(cfg.getNumBlockIDs()),
-      POV(Ctx.getAnalysis<PostOrderCFGView>()) {}
+      POV(Ctx.getAnalysis<PostOrderCFGView>()),
+      worklist(POV->getComparator()) {}
   
   void enqueueBlock(const CFGBlock *block);
   void enqueuePredecessors(const CFGBlock *block);
 
   const CFGBlock *dequeue();
-
-  void sortWorklist();
 };
 
 }
@@ -49,31 +51,22 @@
 void DataflowWorklist::enqueueBlock(const clang::CFGBlock *block) {
   if (block && !enqueuedBlocks[block->getBlockID()]) {
     enqueuedBlocks[block->getBlockID()] = true;
-    worklist.push_back(block);
+    worklist.push(block);
   }
 }
 
 void DataflowWorklist::enqueuePredecessors(const clang::CFGBlock *block) {
-  const unsigned OldWorklistSize = worklist.size();
   for (CFGBlock::const_pred_iterator I = block->pred_begin(),
        E = block->pred_end(); I != E; ++I) {
     enqueueBlock(*I);
   }
-  
-  if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
-    return;
-
-  sortWorklist();
-}
-
-void DataflowWorklist::sortWorklist() {
-  std::sort(worklist.begin(), worklist.end(), POV->getComparator());
 }
 
 const CFGBlock *DataflowWorklist::dequeue() {
   if (worklist.empty())
     return nullptr;
-  const CFGBlock *b = worklist.pop_back_val();
+  const CFGBlock *b = worklist.top();
+  worklist.pop();
   enqueuedBlocks[b->getBlockID()] = false;
   return b;
 }
@@ -528,8 +521,6 @@
       }
   }
   
-  worklist.sortWorklist();
-  
   while (const CFGBlock *block = worklist.dequeue()) {
     // Determine if the block's end value has changed.  If not, we
     // have nothing left to do for this block.