diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 3031d45..491a22c 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -63,6 +63,8 @@
     virtual void releaseMemory() {
       ScopeMap.clear();
       Exps.clear();
+      AllocatableRegs.clear();
+      ReservedRegs.clear();
     }
 
   private:
@@ -76,6 +78,8 @@
     ScopedHTType VNT;
     SmallVector<MachineInstr*, 64> Exps;
     unsigned CurrVN;
+    BitVector AllocatableRegs;
+    BitVector ReservedRegs;
 
     bool PerformTrivialCoalescing(MachineInstr *MI, MachineBasicBlock *MBB);
     bool isPhysDefTriviallyDead(unsigned Reg,
@@ -236,9 +240,9 @@
       return false;
 
     for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i) {
-      if (TRI->isInAllocatableClass(PhysDefs[i]))
-        // Avoid extending live range of physical registers unless
-        // they are unallocatable.
+      if (AllocatableRegs.test(PhysDefs[i]) || ReservedRegs.test(PhysDefs[i]))
+        // Avoid extending live range of physical registers if they are
+        //allocatable or reserved.
         return false;
     }
     CrossMBB = true;
@@ -588,5 +592,7 @@
   MRI = &MF.getRegInfo();
   AA = &getAnalysis<AliasAnalysis>();
   DT = &getAnalysis<MachineDominatorTree>();
+  AllocatableRegs = TRI->getAllocatableSet(MF);
+  ReservedRegs = TRI->getReservedRegs(MF);
   return PerformCSE(DT->getRootNode());
 }