diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -325,7 +325,7 @@
   const MachineFunction *CurFn = nullptr;
 
   /// If nonnull, stores the CU in which the previous subprogram was contained.
-  const DwarfCompileUnit *PrevCU;
+  const DwarfCompileUnit *PrevCU = nullptr;
 
   /// As an optimization, there is no need to emit an entry in the directory
   /// table for the same directory as DW_AT_comp_dir.
diff --git a/llvm/test/DebugInfo/ARM/undef-behavior-in-debug-dwarf-debug.ll b/llvm/test/DebugInfo/ARM/undef-behavior-in-debug-dwarf-debug.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/DebugInfo/ARM/undef-behavior-in-debug-dwarf-debug.ll
@@ -0,0 +1,41 @@
+; RUN: valgrind --error-exitcode=1 llc --filetype=obj %s -o -
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7-unknown-linux-android"
+
+; Function Attrs: norecurse nounwind readnone
+define hidden i32 @add(i32 %0, i32 %1) local_unnamed_addr #0 !dbg !9 {
+  call void @llvm.dbg.value(metadata i32 %0, metadata !14, metadata !DIExpression()), !dbg !16
+  call void @llvm.dbg.value(metadata i32 %1, metadata !15, metadata !DIExpression()), !dbg !16
+  %3 = add nsw i32 %1, %0, !dbg !17
+  ret i32 %3, !dbg !18
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { norecurse nounwind readnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="none" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+armv7-a,+d32,+dsp,+fp64,+neon,+vfp2,+vfp2sp,+vfp3,+vfp3d16,+vfp3d16sp,+vfp3sp,-crypto,-fp-armv8,-fp-armv8d16,-fp-armv8d16sp,-fp-armv8sp,-fp16,-fp16fml,-fullfp16,-thumb-mode,-vfp4,-vfp4d16,-vfp4d16sp,-vfp4sp" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable willreturn }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6, !7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 (https://github.com/llvm/llvm-project.git 6dd738e2f0609f7d3313b574a1d471263d2d3ba1)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "1.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 7, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{i32 1, !"min_enum_size", i32 4}
+!7 = !{i32 7, !"PIC Level", i32 2}
+!8 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 6dd738e2f0609f7d3313b574a1d471263d2d3ba1)"}
+!9 = distinct !DISubprogram(name: "add", scope: !1, file: !1, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !13)
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12, !12, !12}
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !{!14, !15}
+!14 = !DILocalVariable(name: "a", arg: 1, scope: !9, file: !1, line: 1, type: !12)
+!15 = !DILocalVariable(name: "b", arg: 2, scope: !9, file: !1, line: 1, type: !12)
+!16 = !DILocation(line: 0, scope: !9)
+!17 = !DILocation(line: 2, column: 12, scope: !9)
+!18 = !DILocation(line: 2, column: 3, scope: !9)