diff --git a/lib/CodeGen/ProcessImplicitDefs.cpp b/lib/CodeGen/ProcessImplicitDefs.cpp
index 75875d2..62f525f 100644
--- a/lib/CodeGen/ProcessImplicitDefs.cpp
+++ b/lib/CodeGen/ProcessImplicitDefs.cpp
@@ -46,7 +46,7 @@
                                                  const TargetInstrInfo *tii_) {
   unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
   if (tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubReg, DstSubReg) &&
-      Reg == SrcReg)
+      Reg == SrcReg && SrcSubReg == 0 && DstSubReg == 0)
     return true;
 
   if (OpIdx == 2 && MI->isSubregToReg())
@@ -220,7 +220,7 @@
         // Turn a copy use into an implicit_def.
         unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
         if (tii_->isMoveInstr(*RMI, SrcReg, DstReg, SrcSubReg, DstSubReg) &&
-            Reg == SrcReg) {
+            Reg == SrcReg && SrcSubReg == 0 && DstSubReg == 0) {
           RMI->setDesc(tii_->get(TargetOpcode::IMPLICIT_DEF));
 
           bool isKill = false;