diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 9f5f66e37c8..8ba31945058 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -2016,6 +2016,13 @@ X86InstrInfo::convertToThreeAddress(MachineFunction::iterator &MFI,
                         .addReg(Dest, RegState::Define |
                                 getDeadRegState(isDead)),
                         Src, isKill, Src2, isKill2);
+
+      // Preserve undefness of the operands.
+      bool isUndef = MI->getOperand(1).isUndef();
+      bool isUndef2 = MI->getOperand(2).isUndef();
+      NewMI->getOperand(1).setIsUndef(isUndef);
+      NewMI->getOperand(3).setIsUndef(isUndef2);
+
       if (LV && isKill2)
         LV->replaceKillInstruction(Src2, MI, NewMI);
       break;
diff --git a/test/CodeGen/X86/2012-07-16-LeaUndef.ll b/test/CodeGen/X86/2012-07-16-LeaUndef.ll
new file mode 100644
index 00000000000..9e5cbd2f337
--- /dev/null
+++ b/test/CodeGen/X86/2012-07-16-LeaUndef.ll
@@ -0,0 +1,16 @@
+; RUN: llc < %s -march=x86-64 -mcpu=corei7
+
+define void @autogen_SD2543() {
+A:
+  %E83 = add i32 0, 1
+  %E820 = add i32 0, undef
+  br label %C
+C:
+  %B908 = add i32 %E83, %E820
+  store i32 %B908, i32* undef
+  %Sl2391 = select i1 undef, i32 undef, i32 %E83
+  %Cmp3114 = icmp ne i32 %Sl2391, undef
+  br i1 %Cmp3114, label %C, label %G
+G:
+  ret void
+}