diff --git a/lib/Target/X86/InstSelectSimple.cpp b/lib/Target/X86/InstSelectSimple.cpp
index 24c841d2881..d66f7c225e4 100644
--- a/lib/Target/X86/InstSelectSimple.cpp
+++ b/lib/Target/X86/InstSelectSimple.cpp
@@ -646,6 +646,8 @@ bool ISel::EmitComparisonGetSignedness(unsigned OpNum, Value *Op0, Value *Op1) {
       BuildMI(BB, SetCCOpcodeTab[0][OpNum], 0, X86::AL);
       BuildMI(BB, X86::CMPrr32, 2).addReg(Op0r+1).addReg(Op1r+1);
       BuildMI(BB, SetCCOpcodeTab[isSigned][OpNum], 0, X86::BL);
+      BuildMI(BB, X86::IMPLICIT_DEF, 0, X86::BH);
+      BuildMI(BB, X86::IMPLICIT_DEF, 0, X86::AH);
       BuildMI(BB, X86::CMOVErr16, 2, X86::BX).addReg(X86::BX).addReg(X86::AX);
       // NOTE: visitSetCondInst knows that the value is dumped into the BL
       // register at this point for long values...
diff --git a/lib/Target/X86/X86CodeEmitter.cpp b/lib/Target/X86/X86CodeEmitter.cpp
index 41289540ce1..50b1faac8b3 100644
--- a/lib/Target/X86/X86CodeEmitter.cpp
+++ b/lib/Target/X86/X86CodeEmitter.cpp
@@ -470,7 +470,7 @@ void Emitter::emitInstruction(MachineInstr &MI) {
   switch (Desc.TSFlags & X86II::FormMask) {
   default: assert(0 && "Unknown FormMask value in X86 MachineCodeEmitter!");
   case X86II::Pseudo:
-    if (Opcode != X86::IMPLICIT_USE)
+    if (Opcode != X86::IMPLICIT_USE && Opcode != X86::IMPLICIT_DEF)
       std::cerr << "X86 Machine Code Emitter: No 'form', not emitting: " << MI;
     break;
 
diff --git a/lib/Target/X86/X86ISelSimple.cpp b/lib/Target/X86/X86ISelSimple.cpp
index 24c841d2881..d66f7c225e4 100644
--- a/lib/Target/X86/X86ISelSimple.cpp
+++ b/lib/Target/X86/X86ISelSimple.cpp
@@ -646,6 +646,8 @@ bool ISel::EmitComparisonGetSignedness(unsigned OpNum, Value *Op0, Value *Op1) {
       BuildMI(BB, SetCCOpcodeTab[0][OpNum], 0, X86::AL);
       BuildMI(BB, X86::CMPrr32, 2).addReg(Op0r+1).addReg(Op1r+1);
       BuildMI(BB, SetCCOpcodeTab[isSigned][OpNum], 0, X86::BL);
+      BuildMI(BB, X86::IMPLICIT_DEF, 0, X86::BH);
+      BuildMI(BB, X86::IMPLICIT_DEF, 0, X86::AH);
       BuildMI(BB, X86::CMOVErr16, 2, X86::BX).addReg(X86::BX).addReg(X86::AX);
       // NOTE: visitSetCondInst knows that the value is dumped into the BL
       // register at this point for long values...
diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index fd544670dec..396464660a1 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -107,6 +107,7 @@ def NOOP : X86Inst<"nop", 0x90, RawFrm, NoArg>;    // nop
 def ADJCALLSTACKDOWN : X86Inst<"ADJCALLSTACKDOWN", 0, Pseudo, NoArg>;
 def ADJCALLSTACKUP   : X86Inst<"ADJCALLSTACKUP",   0, Pseudo, NoArg>;
 def IMPLICIT_USE     : X86Inst<"IMPLICIT_USE",     0, Pseudo, NoArg>;
+def IMPLICIT_DEF     : X86Inst<"IMPLICIT_DEF",     0, Pseudo, NoArg>;
 
 //===----------------------------------------------------------------------===//
 //  Control Flow Instructions...