diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 90887a0772a..805ef478c3c 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -892,7 +892,7 @@ bool TargetLowering::SimplifyDemandedBits(SDOperand Op,
     MVT::ValueType InVT = Op.getOperand(0).getValueType();
     unsigned InBits = MVT::getSizeInBits(InVT);
     APInt InMask    = APInt::getLowBitsSet(BitWidth, InBits);
-    APInt InSignBit = APInt::getLowBitsSet(BitWidth, InBits);
+    APInt InSignBit = APInt::getBitsSet(BitWidth, InBits - 1, InBits);
     APInt NewBits   = ~InMask & NewMask;
     
     // If none of the top bits are demanded, convert this into an any_extend.
diff --git a/test/CodeGen/X86/sext-select.ll b/test/CodeGen/X86/sext-select.ll
new file mode 100644
index 00000000000..839ebc2b6c1
--- /dev/null
+++ b/test/CodeGen/X86/sext-select.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep movsw
+; PR2139
+
+declare void @abort()
+
+define i32 @main() {
+entry:
+	%tmp73 = tail call i1 @return_false()		; <i8> [#uses=1]
+	%g.0 = select i1 %tmp73, i16 0, i16 -480		; <i16> [#uses=2]
+	%tmp7778 = sext i16 %g.0 to i32		; <i32> [#uses=1]
+	%tmp80 = shl i32 %tmp7778, 3		; <i32> [#uses=2]
+	%tmp87 = icmp sgt i32 %tmp80, 32767		; <i1> [#uses=1]
+	br i1 %tmp87, label %bb90, label %bb91
+bb90:		; preds = %bb84, %bb72
+	tail call void @abort()
+	unreachable
+bb91:		; preds = %bb84
+	ret i32 0
+}
+
+define i1 @return_false() {
+	ret i1 0
+}