diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index 98f485045f6..972cf13a240 100644
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -155,6 +155,9 @@ static bool isLiveInButUnusedBefore(unsigned Reg, MachineInstr *MI,
   SmallPtrSet<MachineInstr*, 4> UsesInMBB;
   for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
          UE = MRI->use_end(); UI != UE; ++UI) {
+    MachineOperand &UseMO = UI.getOperand();
+    if (UseMO.isReg() && UseMO.isUndef())
+      continue;
     MachineInstr *UseMI = &*UI;
     if (UseMI->getParent() == MBB)
       UsesInMBB.insert(UseMI);
diff --git a/test/CodeGen/ARM/2009-07-22-ScavengerAssert.ll b/test/CodeGen/ARM/2009-07-22-ScavengerAssert.ll
new file mode 100644
index 00000000000..5dd336b9f6e
--- /dev/null
+++ b/test/CodeGen/ARM/2009-07-22-ScavengerAssert.ll
@@ -0,0 +1,94 @@
+; RUN: llvm-as < %s | llc -mtriple=armv6-apple-darwin10
+
+	%struct.cli_ac_alt = type { i8, i8*, i16, i16, %struct.cli_ac_alt* }
+	%struct.cli_ac_node = type { i8, i8, %struct.cli_ac_patt*, %struct.cli_ac_node**, %struct.cli_ac_node* }
+	%struct.cli_ac_patt = type { i16*, i16*, i16, i16, i8, i32, i32, i8*, i8*, i32, i16, i16, i16, i16, %struct.cli_ac_alt**, i8, i16, %struct.cli_ac_patt*, %struct.cli_ac_patt* }
+	%struct.cli_bm_patt = type { i8*, i8*, i16, i16, i8*, i8*, i8, %struct.cli_bm_patt*, i16 }
+	%struct.cli_matcher = type { i16, i8, i8*, %struct.cli_bm_patt**, i32*, i32, i8, i8, %struct.cli_ac_node*, %struct.cli_ac_node**, %struct.cli_ac_patt**, i32, i32, i32 }
+
+declare arm_apcscc i32 @strlen(i8* nocapture) nounwind readonly
+
+define arm_apcscc i32 @cli_ac_addsig(%struct.cli_matcher* nocapture %root, i8* %virname, i8* %hexsig, i32 %sigid, i16 zeroext %parts, i16 zeroext %partno, i16 zeroext %type, i32 %mindist, i32 %maxdist, i8* %offset, i8 zeroext %target) nounwind {
+entry:
+	br i1 undef, label %bb126, label %bb1
+
+bb1:		; preds = %entry
+	br i1 undef, label %cli_calloc.exit.thread, label %cli_calloc.exit
+
+cli_calloc.exit.thread:		; preds = %bb1
+	ret i32 -114
+
+cli_calloc.exit:		; preds = %bb1
+	store i16 %parts, i16* undef, align 4
+	br i1 undef, label %bb52, label %bb4
+
+bb4:		; preds = %cli_calloc.exit
+	br i1 undef, label %bb.i, label %bb1.i3
+
+bb.i:		; preds = %bb4
+	unreachable
+
+bb1.i3:		; preds = %bb4
+	br i1 undef, label %bb2.i4, label %cli_strdup.exit
+
+bb2.i4:		; preds = %bb1.i3
+	ret i32 -114
+
+cli_strdup.exit:		; preds = %bb1.i3
+	br i1 undef, label %cli_calloc.exit54.thread, label %cli_calloc.exit54
+
+cli_calloc.exit54.thread:		; preds = %cli_strdup.exit
+	ret i32 -114
+
+cli_calloc.exit54:		; preds = %cli_strdup.exit
+	br label %bb45
+
+cli_calloc.exit70.thread:		; preds = %bb45
+	unreachable
+
+cli_calloc.exit70:		; preds = %bb45
+	br i1 undef, label %bb.i83, label %bb1.i84
+
+bb.i83:		; preds = %cli_calloc.exit70
+	unreachable
+
+bb1.i84:		; preds = %cli_calloc.exit70
+	br i1 undef, label %bb2.i85, label %bb17
+
+bb2.i85:		; preds = %bb1.i84
+	unreachable
+
+bb17:		; preds = %bb1.i84
+	br i1 undef, label %bb22, label %bb.nph
+
+bb.nph:		; preds = %bb17
+	br label %bb18
+
+bb18:		; preds = %bb18, %bb.nph
+	br i1 undef, label %bb18, label %bb22
+
+bb22:		; preds = %bb18, %bb17
+	br i1 undef, label %bb25, label %bb43.preheader
+
+bb43.preheader:		; preds = %bb22
+	br i1 undef, label %bb28, label %bb45
+
+bb25:		; preds = %bb22
+	unreachable
+
+bb28:		; preds = %bb43.preheader
+	unreachable
+
+bb45:		; preds = %bb43.preheader, %cli_calloc.exit54
+	br i1 undef, label %cli_calloc.exit70.thread, label %cli_calloc.exit70
+
+bb52:		; preds = %cli_calloc.exit
+	%0 = load i16* undef, align 4		; <i16> [#uses=1]
+	%1 = icmp eq i16 %0, 0		; <i1> [#uses=1]
+	%iftmp.20.0 = select i1 %1, i8* %hexsig, i8* null		; <i8*> [#uses=1]
+	%2 = tail call arm_apcscc  i32 @strlen(i8* %iftmp.20.0) nounwind readonly		; <i32> [#uses=0]
+	unreachable
+
+bb126:		; preds = %entry
+	ret i32 -117
+}