diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 3ce45f7d5d67e..00291147b6868 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -162,8 +162,8 @@ class AsmParser : public MCAsmParser {
   };
   CppHashInfoTy CppHashInfo;
 
-  /// The filename from the first cpp hash file line comment, if any.
-  StringRef FirstCppHashFilename;
+  /// Have we seen any file line comment.
+  bool HadCppHashFilename = false;
 
   /// List of forward directional labels for diagnosis at the end.
   SmallVector<std::tuple<SMLoc, CppHashInfoTy, MCSymbol *>, 4> DirLabels;
@@ -952,12 +952,6 @@ bool AsmParser::enabledGenDwarfForAssembly() {
   // the assembler source was produced with debug info already) then emit one
   // describing the assembler source file itself.
   if (getContext().getGenDwarfFileNumber() == 0) {
-    // Use the first #line directive for this, if any. It's preprocessed, so
-    // there is no checksum, and of course no source directive.
-    if (!FirstCppHashFilename.empty())
-      getContext().setMCLineTableRootFile(
-          /*CUID=*/0, getContext().getCompilationDir(), FirstCppHashFilename,
-          /*Cksum=*/std::nullopt, /*Source=*/std::nullopt);
     const MCDwarfFile &RootFile =
         getContext().getMCDwarfLineTable(/*CUID=*/0).getRootFile();
     getContext().setGenDwarfFileNumber(getStreamer().emitDwarfFileDirective(
@@ -2440,8 +2434,19 @@ bool AsmParser::parseCppHashLineFilenameComment(SMLoc L, bool SaveLocInfo) {
   CppHashInfo.Filename = Filename;
   CppHashInfo.LineNumber = LineNumber;
   CppHashInfo.Buf = CurBuffer;
-  if (FirstCppHashFilename.empty())
-    FirstCppHashFilename = Filename;
+  if (!HadCppHashFilename) {
+    HadCppHashFilename = true;
+    // If we haven't encountered any .file directives, then the first #line
+    // directive describes the "root" file and directory of the compilation
+    // unit.
+    if (getContext().getGenDwarfFileNumber() == 0) {
+      // It's preprocessed, so there is no checksum, and of course no source
+      // directive.
+      getContext().setMCLineTableRootFile(
+          /*CUID=*/0, getContext().getCompilationDir(), Filename,
+          /*Cksum=*/std::nullopt, /*Source=*/std::nullopt);
+    }
+  }
   return false;
 }
 
diff --git a/llvm/test/MC/ELF/debug-hash-file-empty-dwarf.s b/llvm/test/MC/ELF/debug-hash-file-empty-dwarf.s
new file mode 100644
index 0000000000000..cc1c3d1796b6e
--- /dev/null
+++ b/llvm/test/MC/ELF/debug-hash-file-empty-dwarf.s
@@ -0,0 +1,26 @@
+// RUN: llvm-mc -triple x86_64-unknown-linux-gnu -filetype obj -g -dwarf-version 5 -o %t %s
+// RUN: llvm-dwarfdump -debug-info -debug-line %t | FileCheck %s
+
+// CHECK-NOT: DW_TAG_
+
+// CHECK:      include_directories[ 0] =
+// CHECK-NOT:  include_directories[ 1] =
+// CHECK:      file_names[ 0]:
+// CHECK-NEXT:           name: "/MyTest/Inputs/other.S"
+// CHECK-NEXT:      dir_index: 0
+// CHECK-NOT:  file_names[ 1]:
+
+// RUN: llvm-mc -triple=x86_64 -filetype=obj -g -dwarf-version=5 -fdebug-prefix-map=/MyTest=/src_root %s -o %t.5.o
+// RUN: llvm-dwarfdump -debug-info -debug-line %t.5.o | FileCheck %s --check-prefixes=MAP
+
+// MAP-NOT: DW_TAG_
+
+// MAP:      include_directories[  0] = "{{.*}}"
+// MAP-NEXT: file_names[  0]:
+// MAP-NEXT:            name: "/src_root/Inputs/other.S"
+// MAP-NEXT:       dir_index: 0
+
+# 1 "/MyTest/Inputs/other.S"
+
+.section .data
+.asciz "data"