diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 0c790f63150..b608186338e 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -101,6 +101,20 @@ namespace {
         Add(I);
     }
     
+    /// AddInitialGroup - Add the specified batch of stuff in reverse order.
+    /// which should only be done when the worklist is empty and when the group
+    /// has no duplicates.
+    void AddInitialGroup(Instruction *const *List, unsigned NumEntries) {
+      assert(Worklist.empty() && "Worklist must be empty to add initial group");
+      Worklist.reserve(NumEntries+16);
+      DEBUG(errs() << "IC: ADDING: " << NumEntries << " instrs to worklist\n");
+      for (; NumEntries; --NumEntries) {
+        Instruction *I = List[NumEntries-1];
+        WorklistMap.insert(std::make_pair(I, Worklist.size()));
+        Worklist.push_back(I);
+      }
+    }
+    
     // Remove - remove I from the worklist if it exists.
     void Remove(Instruction *I) {
       DenseMap<Instruction*, unsigned>::iterator It = WorklistMap.find(I);
@@ -12663,6 +12677,9 @@ static void AddReachableCodeToWorklist(BasicBlock *BB,
                                        const TargetData *TD) {
   SmallVector<BasicBlock*, 256> Worklist;
   Worklist.push_back(BB);
+  
+  std::vector<Instruction*> InstrsForInstCombineWorklist;
+  InstrsForInstCombineWorklist.reserve(128);
 
   while (!Worklist.empty()) {
     BB = Worklist.back();
@@ -12709,7 +12726,7 @@ static void AddReachableCodeToWorklist(BasicBlock *BB,
         DBI_Prev = 0;
       }
 
-      IC.Worklist.Add(Inst);
+      InstrsForInstCombineWorklist.push_back(Inst);
     }
 
     // Recursively visit successors.  If this is a branch or switch on a
@@ -12741,6 +12758,14 @@ static void AddReachableCodeToWorklist(BasicBlock *BB,
     for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
       Worklist.push_back(TI->getSuccessor(i));
   }
+  
+  // Once we've found all of the instructions to add to instcombine's worklist,
+  // add them in reverse order.  This way instcombine will visit from the top
+  // of the function down.  This jives well with the way that it adds all uses
+  // of instructions to the worklist after doing a transformation, thus avoiding
+  // some N^2 behavior in pathological cases.
+  IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
+                              InstrsForInstCombineWorklist.size());
 }
 
 bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {