diff --git a/lib/CodeGen/ProcessImplicitDefs.cpp b/lib/CodeGen/ProcessImplicitDefs.cpp
index 23b78c7..455964b 100644
--- a/lib/CodeGen/ProcessImplicitDefs.cpp
+++ b/lib/CodeGen/ProcessImplicitDefs.cpp
@@ -77,6 +77,7 @@
   SmallVector<MachineInstr*, 8> ImpDefMIs;
   MachineBasicBlock *Entry = fn.begin();
   SmallPtrSet<MachineBasicBlock*,16> Visited;
+  SmallPtrSet<MachineInstr*, 8> ModInsts;
 
   for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
          DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
@@ -201,6 +202,8 @@
         MachineOperand &RMO = UI.getOperand();
         MachineInstr *RMI = &*UI;
         ++UI;
+        if (ModInsts.count(RMI))
+          continue;
         MachineBasicBlock *RMBB = RMI->getParent();
         if (RMBB == MBB)
           continue;
@@ -216,6 +219,7 @@
           RMI->setDesc(tii_->get(TargetInstrInfo::IMPLICIT_DEF));
           for (int j = RMI->getNumOperands() - 1, ee = 0; j > ee; --j)
             RMI->RemoveOperand(j);
+          ModInsts.insert(RMI);
           continue;
         }
 
@@ -226,6 +230,7 @@
         RMO.setIsKill();
       }
     }
+    ModInsts.clear();
     ImpDefRegs.clear();
     ImpDefMIs.clear();
   }