diff --git a/include/llvm/CodeGen/MachineInstr.h b/include/llvm/CodeGen/MachineInstr.h
index ffec00fd8cf..5e62f0bcfb8 100644
--- a/include/llvm/CodeGen/MachineInstr.h
+++ b/include/llvm/CodeGen/MachineInstr.h
@@ -338,7 +338,7 @@ public:
   /// addRegisterDefined - We have determined MI defines a register. Make sure
   /// there is an operand defining Reg.
   void addRegisterDefined(unsigned IncomingReg,
-                          const TargetRegisterInfo *RegInfo);
+                          const TargetRegisterInfo *RegInfo = 0);
 
   /// isSafeToMove - Return true if it is safe to move this instruction. If
   /// SawStore is set to true, it means that there is a store (or call) between
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index fd933cedd0e..c07802ee26b 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -320,6 +320,12 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
     // of inputs.
     if (MO.isEarlyClobber())
       defIndex = MIIdx.getUseIndex();
+
+    // Make sure the first definition is not a partial redefinition. Add an
+    // <imp-def> of the full register.
+    if (MO.getSubReg())
+      mi->addRegisterDefined(interval.reg);
+
     MachineInstr *CopyMI = NULL;
     unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
     if (mi->isExtractSubreg() || mi->isInsertSubreg() || mi->isSubregToReg() ||
@@ -1371,7 +1377,8 @@ rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
       MI->eraseFromParent();
       continue;
     }
-    assert(!O.isImplicit() && "Spilling register that's used as implicit use?");
+    assert(!(O.isImplicit() && O.isUse()) &&
+           "Spilling register that's used as implicit use?");
     SlotIndex index = getInstructionIndex(MI);
     if (index < start || index >= end)
       continue;
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index 553b13938c9..595fddda6f6 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -1388,11 +1388,21 @@ bool MachineInstr::addRegisterDead(unsigned IncomingReg,
 
 void MachineInstr::addRegisterDefined(unsigned IncomingReg,
                                       const TargetRegisterInfo *RegInfo) {
-  MachineOperand *MO = findRegisterDefOperand(IncomingReg, false, RegInfo);
-  if (!MO || MO->getSubReg())
-    addOperand(MachineOperand::CreateReg(IncomingReg,
-                                         true  /*IsDef*/,
-                                         true  /*IsImp*/));
+  if (TargetRegisterInfo::isPhysicalRegister(IncomingReg)) {
+    MachineOperand *MO = findRegisterDefOperand(IncomingReg, false, RegInfo);
+    if (MO)
+      return;
+  } else {
+    for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
+      const MachineOperand &MO = getOperand(i);
+      if (MO.isReg() && MO.getReg() == IncomingReg && MO.isDef() &&
+          MO.getSubReg() == 0)
+        return;
+    }
+  }
+  addOperand(MachineOperand::CreateReg(IncomingReg,
+                                       true  /*IsDef*/,
+                                       true  /*IsImp*/));
 }
 
 unsigned