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diff --git a/src/mem/ruby/system/PseudoLRUPolicy.hh b/src/mem/ruby/system/PseudoLRUPolicy.hh
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+
+#ifndef PSEUDOLRUPOLICY_H
+#define PSEUDOLRUPOLICY_H
+
+#include "AbstractReplacementPolicy.hh"
+
+/**
+ * Implementation of tree-based pseudo-LRU replacement
+ *
+ * Works for any associativity between 1 and 128.
+ *
+ * Also implements associativities that are not a power of 2 by
+ * ignoring paths that lead to a larger index (i.e. truncating the
+ * tree).  Note that when this occurs, the algorithm becomes less
+ * fair, as it will favor indicies in the larger (by index) half of
+ * the associative set. This is most unfair when the nearest power of
+ * 2 is one below the associativy, and most fair when it is one above.
+ */
+
+class PseudoLRUPolicy : public AbstractReplacementPolicy {
+ public:
+
+  PseudoLRUPolicy(Index num_sets, Index assoc);
+  ~PseudoLRUPolicy();
+
+  void touch(Index set, Index way, Time time);
+  Index getVictim(Index set) const;
+
+ private:
+  unsigned int m_effective_assoc;    /** nearest (to ceiling) power of 2 */
+  unsigned int m_num_levels;         /** number of levels in the tree */
+  uint64* m_trees;                   /** bit representation of the trees, one for each set */
+};
+
+inline
+PseudoLRUPolicy::PseudoLRUPolicy(Index num_sets, Index assoc)
+  : AbstractReplacementPolicy(num_sets, assoc)
+{
+  int num_tree_nodes;
+
+  // associativity cannot exceed capacity of tree representation
+  assert(num_sets > 0 && assoc > 1 && assoc <= (Index) sizeof(uint64)*4);
+
+  m_trees = NULL;
+  m_num_levels = 0;
+
+  m_effective_assoc = 1;
+  while(m_effective_assoc < assoc){
+    m_effective_assoc <<= 1;  // effective associativity is ceiling power of 2
+  }
+  assoc = m_effective_assoc;
+  while(true){
+    assoc /= 2;
+    if(!assoc) break;
+    m_num_levels++;
+  }
+  assert(m_num_levels < sizeof(unsigned int)*4);
+  num_tree_nodes = ((int)pow(2, m_num_levels))-1;
+  m_trees = new uint64[m_num_sets];
+  for(unsigned int i=0; i< m_num_sets; i++){
+    m_trees[i] = 0;
+  }
+}
+
+inline
+PseudoLRUPolicy::~PseudoLRUPolicy()
+{
+  if(m_trees != NULL)
+    delete[] m_trees;
+}
+
+inline
+void PseudoLRUPolicy::touch(Index set, Index index, Time time){
+  assert(index >= 0 && index < m_assoc);
+  assert(set >= 0 && set < m_num_sets);
+
+  int tree_index = 0;
+  int node_val;
+  for(int i=m_num_levels -1; i>=0; i--){
+    node_val = (index >> i)&1;
+    if(node_val)
+      m_trees[set] |= node_val << tree_index;
+    else
+      m_trees[set] &= ~(1 << tree_index);
+    tree_index = node_val ? (tree_index*2)+2 : (tree_index*2)+1;
+  }
+  m_last_ref_ptr[set][index] = time;
+}
+
+inline
+Index PseudoLRUPolicy::getVictim(Index set) const {
+  //  assert(m_assoc != 0);
+
+  Index index = 0;
+
+  int tree_index = 0;
+  int node_val;
+  for(unsigned int i=0;i<m_num_levels;i++){
+    node_val = (m_trees[set]>>tree_index)&1;
+    index += node_val?0:(m_effective_assoc >> (i+1));
+    tree_index = node_val? (tree_index*2)+1 : (tree_index*2)+2;
+  }
+  assert(index >= 0 && index < m_effective_assoc);
+
+  /* return either the found index or the max possible index */
+  /* NOTE: this is not a fair replacement when assoc is not a power of 2 */
+  return (index > (m_assoc-1)) ? m_assoc-1:index;
+}
+
+#endif // PSEUDOLRUPOLICY_H