diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 6a9f428..734a06f 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -160,6 +160,8 @@
     // Realize that the destination register is defined by the PHI copy now, not
     // the PHI itself.
     LV->getVarInfo(DestReg).DefInst = PHICopy;
+
+    LV->getVarInfo(IncomingReg).UsedBlocks[MBB.getNumber()] = true;
   }
 
   // Adjust the VRegPHIUseCount map to account for the removal of this PHI
@@ -210,6 +212,7 @@
     // instruction kills the incoming value.
     //
     LiveVariables::VarInfo &InRegVI = LV->getVarInfo(SrcReg);
+    InRegVI.UsedBlocks[opBlock.getNumber()] = true;
 
     // Loop over all of the successors of the basic block, checking to see
     // if the value is either live in the block, or if it is killed in the
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index ba768ba..9209420 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -198,6 +198,9 @@
           varInfo.DefInst = prevMi;
 
           // update live variables for regB
+          LiveVariables::VarInfo& varInfoB = LV.getVarInfo(regB);
+          // regB is used in this BB.
+          varInfoB.UsedBlocks[mbbi->getNumber()] = true;
           if (LV.removeVirtualRegisterKilled(regB, mbbi, mi))
             LV.addVirtualRegisterKilled(regB, prevMi);