diff --git a/include/llvm/ADT/PostOrderIterator.h b/include/llvm/ADT/PostOrderIterator.h
index 8315bc9f9ed..575786fa682 100644
--- a/include/llvm/ADT/PostOrderIterator.h
+++ b/include/llvm/ADT/PostOrderIterator.h
@@ -18,8 +18,8 @@
 
 #include "llvm/ADT/GraphTraits.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
 #include <set>
-#include <stack>
 #include <vector>
 
 namespace llvm {
@@ -52,21 +52,21 @@ class po_iterator : public std::iterator<std::forward_iterator_tag,
 
   // VisitStack - Used to maintain the ordering.  Top = current block
   // First element is basic block pointer, second is the 'next child' to visit
-  std::stack<std::pair<NodeType *, ChildItTy> > VisitStack;
+  SmallVector<std::pair<NodeType *, ChildItTy>, 16> VisitStack;
 
   void traverseChild() {
-    while (VisitStack.top().second != GT::child_end(VisitStack.top().first)) {
-      NodeType *BB = *VisitStack.top().second++;
+    while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
+      NodeType *BB = *VisitStack.back().second++;
       if (!this->Visited.count(BB)) {  // If the block is not visited...
         this->Visited.insert(BB);
-        VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
+        VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
       }
     }
   }
 
   inline po_iterator(NodeType *BB) {
     this->Visited.insert(BB);
-    VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
+    VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
     traverseChild();
   }
   inline po_iterator() {} // End is when stack is empty.
@@ -75,7 +75,7 @@ class po_iterator : public std::iterator<std::forward_iterator_tag,
     po_iterator_storage<SetType, ExtStorage>(S) {
     if(!S.count(BB)) {
       this->Visited.insert(BB);
-      VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
+      VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
       traverseChild();
     }
   }
@@ -102,7 +102,7 @@ public:
   inline bool operator!=(const _Self& x) const { return !operator==(x); }
 
   inline pointer operator*() const {
-    return VisitStack.top().first;
+    return VisitStack.back().first;
   }
 
   // This is a nonstandard operator-> that dereferences the pointer an extra
@@ -112,7 +112,7 @@ public:
   inline NodeType *operator->() const { return operator*(); }
 
   inline _Self& operator++() {   // Preincrement
-    VisitStack.pop();
+    VisitStack.pop_back();
     if (!VisitStack.empty())
       traverseChild();
     return *this;
diff --git a/include/llvm/Analysis/IntervalIterator.h b/include/llvm/Analysis/IntervalIterator.h
index d842840b66b..f0130efd6d0 100644
--- a/include/llvm/Analysis/IntervalIterator.h
+++ b/include/llvm/Analysis/IntervalIterator.h
@@ -33,10 +33,10 @@
 #ifndef LLVM_INTERVAL_ITERATOR_H
 #define LLVM_INTERVAL_ITERATOR_H
 
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/Analysis/IntervalPartition.h"
 #include "llvm/Function.h"
 #include "llvm/Support/CFG.h"
-#include <stack>
 #include <set>
 #include <algorithm>
 
@@ -88,7 +88,7 @@ inline void addNodeToInterval(Interval *Int, Interval *I) {
 template<class NodeTy, class OrigContainer_t, class GT = GraphTraits<NodeTy*>,
          class IGT = GraphTraits<Inverse<NodeTy*> > >
 class IntervalIterator {
-  std::stack<std::pair<Interval*, typename Interval::succ_iterator> > IntStack;
+  SmallVector<std::pair<Interval*, typename Interval::succ_iterator>, 16> IntStack;
   std::set<BasicBlock*> Visited;
   OrigContainer_t *OrigContainer;
   bool IOwnMem;     // If True, delete intervals when done with them
@@ -116,15 +116,15 @@ public:
     if (IOwnMem)
       while (!IntStack.empty()) {
         delete operator*();
-        IntStack.pop();
+        IntStack.pop_back();
       }
   }
 
   inline bool operator==(const _Self& x) const { return IntStack == x.IntStack;}
   inline bool operator!=(const _Self& x) const { return !operator==(x); }
 
-  inline const Interval *operator*() const { return IntStack.top().first; }
-  inline       Interval *operator*()       { return IntStack.top().first; }
+  inline const Interval *operator*() const { return IntStack.back().first; }
+  inline       Interval *operator*()       { return IntStack.back().first; }
   inline const Interval *operator->() const { return operator*(); }
   inline       Interval *operator->()       { return operator*(); }
 
@@ -133,8 +133,8 @@ public:
     do {
       // All of the intervals on the stack have been visited.  Try visiting
       // their successors now.
-      Interval::succ_iterator &SuccIt = IntStack.top().second,
-                                EndIt = succ_end(IntStack.top().first);
+      Interval::succ_iterator &SuccIt = IntStack.back().second,
+                                EndIt = succ_end(IntStack.back().first);
       while (SuccIt != EndIt) {                 // Loop over all interval succs
         bool Done = ProcessInterval(getSourceGraphNode(OrigContainer, *SuccIt));
         ++SuccIt;                               // Increment iterator
@@ -142,10 +142,10 @@ public:
       }
 
       // Free interval memory... if necessary
-      if (IOwnMem) delete IntStack.top().first;
+      if (IOwnMem) delete IntStack.back().first;
 
       // We ran out of successors for this interval... pop off the stack
-      IntStack.pop();
+      IntStack.pop_back();
     } while (!IntStack.empty());
 
     return *this;
@@ -175,7 +175,7 @@ private:
            E = GT::child_end(Node); I != E; ++I)
       ProcessNode(Int, getSourceGraphNode(OrigContainer, *I));
 
-    IntStack.push(std::make_pair(Int, succ_begin(Int)));
+    IntStack.push_back(std::make_pair(Int, succ_begin(Int)));
     return true;
   }