diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -2858,6 +2858,14 @@
   CurFn = nullptr;
 }
 
+// Usable locations are valid with non-zero line numbers. A line number of zero
+// corresponds to optimized code that doesn't have a distinct source location.
+// In this case, we try to use the previous or next source location depending on
+// the context.
+static bool isUsableDebugLoc(DebugLoc DL) {
+  return DL && DL.getLine() != 0;
+}
+
 void CodeViewDebug::beginInstruction(const MachineInstr *MI) {
   DebugHandlerBase::beginInstruction(MI);
 
@@ -2869,19 +2877,21 @@
   // If the first instruction of a new MBB has no location, find the first
   // instruction with a location and use that.
   DebugLoc DL = MI->getDebugLoc();
-  if (!DL && MI->getParent() != PrevInstBB) {
+  if (!isUsableDebugLoc(DL) && MI->getParent() != PrevInstBB) {
     for (const auto &NextMI : *MI->getParent()) {
       if (NextMI.isDebugInstr())
         continue;
       DL = NextMI.getDebugLoc();
-      if (DL)
+      if (isUsableDebugLoc(DL))
         break;
     }
+    // FIXME: Handle the case where the BB has no valid locations. This would
+    // probably require doing a real dataflow analysis.
   }
   PrevInstBB = MI->getParent();
 
   // If we still don't have a debug location, don't record a location.
-  if (!DL)
+  if (!isUsableDebugLoc(DL))
     return;
 
   maybeRecordLocation(DL, Asm->MF);
diff --git a/llvm/test/DebugInfo/COFF/line-zero.ll b/llvm/test/DebugInfo/COFF/line-zero.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/DebugInfo/COFF/line-zero.ll
@@ -0,0 +1,77 @@
+; RUN: llc < %s | FileCheck %s
+
+; C++ source to regenerate:
+; int main() {
+;   volatile int x;
+;   x = 1;
+; #line 0
+;   x = 2;
+; #line 7
+;   x = 3;
+; }
+
+
+; CHECK-LABEL: main:                                   # @main
+; CHECK:         .cv_loc 0 1 1 0                 # t.cpp:1:0
+; CHECK:         .cv_loc 0 1 3 0                 # t.cpp:3:0
+; CHECK:         movl    $1, 4(%rsp)
+; CHECK-NOT: .cv_loc {{.*}} t.cpp:0:0
+; CHECK:         movl    $2, 4(%rsp)
+; CHECK:         .cv_loc 0 1 7 0                 # t.cpp:7:0
+; CHECK:         movl    $3, 4(%rsp)
+; CHECK:         .cv_loc 0 1 8 0                 # t.cpp:8:0
+; CHECK:         xorl    %eax, %eax
+; CHECK:         retq
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.22.27905"
+
+; Function Attrs: norecurse nounwind uwtable
+define dso_local i32 @main() local_unnamed_addr #0 !dbg !8 {
+entry:
+  %x = alloca i32, align 4
+  %x.0.x.0..sroa_cast = bitcast i32* %x to i8*, !dbg !15
+  call void @llvm.dbg.declare(metadata i32* %x, metadata !13, metadata !DIExpression()), !dbg !15
+  store volatile i32 1, i32* %x, align 4, !dbg !16, !tbaa !17
+  store volatile i32 2, i32* %x, align 4, !dbg !21, !tbaa !17
+  store volatile i32 3, i32* %x, align 4, !dbg !22, !tbaa !17
+  ret i32 0, !dbg !23
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #2
+
+attributes #0 = { norecurse nounwind uwtable }
+attributes #1 = { argmemonly nounwind willreturn }
+attributes #2 = { nounwind readnone speculatable willreturn }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "t.cpp", directory: "C:\5Csrc\5Cllvm-project\5Cbuild", checksumkind: CSK_MD5, checksum: "8b6d53b166e6fa660f115eff7beedf3b")
+!2 = !{}
+!3 = !{i32 2, !"CodeView", i32 1}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 10.0.0"}
+!8 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !9, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
+!9 = !DISubroutineType(types: !10)
+!10 = !{!11}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !{!13}
+!13 = !DILocalVariable(name: "x", scope: !8, file: !1, line: 2, type: !14)
+!14 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !11)
+!15 = !DILocation(line: 2, scope: !8)
+!16 = !DILocation(line: 3, scope: !8)
+!17 = !{!18, !18, i64 0}
+!18 = !{!"int", !19, i64 0}
+!19 = !{!"omnipotent char", !20, i64 0}
+!20 = !{!"Simple C++ TBAA"}
+!21 = !DILocation(line: 0, scope: !8)
+!22 = !DILocation(line: 7, scope: !8)
+!23 = !DILocation(line: 8, scope: !8)
diff --git a/llvm/test/DebugInfo/COFF/local-variables.ll b/llvm/test/DebugInfo/COFF/local-variables.ll
--- a/llvm/test/DebugInfo/COFF/local-variables.ll
+++ b/llvm/test/DebugInfo/COFF/local-variables.ll
@@ -60,7 +60,7 @@
 ; ASM:         leaq    36(%rsp), %rcx
 ; ASM: [[else_end:\.Ltmp.*]]:
 ; ASM: .LBB0_3:                                # %if.end
-; ASM:         .cv_loc 0 1 0 0                # t.cpp:0:0
+; ASM:         .cv_loc 0 1 17 1                # t.cpp:17:1
 ; ASM:         callq   capture
 ; ASM:         nop
 ; ASM:         addq    $56, %rsp