diff --git a/src/debug/dwarf/line.go b/src/debug/dwarf/line.go
index 4fc1896dbc0..1cd9dd98cf7 100644
--- a/src/debug/dwarf/line.go
+++ b/src/debug/dwarf/line.go
@@ -441,6 +441,19 @@ func (r *LineReader) readFileEntry() (bool, error) {
 	mtime := r.buf.uint()
 	length := int(r.buf.uint())
 
+	// If this is a dynamically added path and the cursor was
+	// backed up, we may have already added this entry. Avoid
+	// updating existing line table entries in this case. This
+	// avoids an allocation and potential racy access to the slice
+	// backing store if the user called Files.
+	if len(r.fileEntries) < cap(r.fileEntries) {
+		fe := r.fileEntries[:len(r.fileEntries)+1]
+		if fe[len(fe)-1] != nil {
+			// We already processed this addition.
+			r.fileEntries = fe
+			return false, nil
+		}
+	}
 	r.fileEntries = append(r.fileEntries, &LineFile{name, mtime, length})
 	return false, nil
 }
@@ -692,6 +705,22 @@ func (r *LineReader) resetState() {
 	r.updateFile()
 }
 
+// Files returns the file name table of this compilation unit as of
+// the current position in the line table. The file name table may be
+// referenced from attributes in this compilation unit such as
+// AttrDeclFile.
+//
+// Entry 0 is always nil, since file index 0 represents "no file".
+//
+// The file name table of a compilation unit is not fixed. Files
+// returns the file table as of the current position in the line
+// table. This may contain more entries than the file table at an
+// earlier position in the line table, though existing entries never
+// change.
+func (r *LineReader) Files() []*LineFile {
+	return r.fileEntries
+}
+
 // ErrUnknownPC is the error returned by LineReader.ScanPC when the
 // seek PC is not covered by any entry in the line table.
 var ErrUnknownPC = errors.New("ErrUnknownPC")
diff --git a/src/debug/dwarf/line_test.go b/src/debug/dwarf/line_test.go
index 11a254464a2..1fd9b19b035 100644
--- a/src/debug/dwarf/line_test.go
+++ b/src/debug/dwarf/line_test.go
@@ -43,8 +43,9 @@ func TestLineELFGCC(t *testing.T) {
 		{Address: 0x40060f, File: file2C, Line: 6, IsStmt: true},
 		{Address: 0x400611, EndSequence: true},
 	}
+	files := [][]*LineFile{{nil, file1H, file1C}, {nil, file2C}}
 
-	testLineTable(t, want, elfData(t, "testdata/line-gcc.elf"))
+	testLineTable(t, want, files, elfData(t, "testdata/line-gcc.elf"))
 }
 
 func TestLineGCCWindows(t *testing.T) {
@@ -83,8 +84,9 @@ func TestLineGCCWindows(t *testing.T) {
 		{Address: 0x401595, File: file2C, Line: 6, IsStmt: true},
 		{Address: 0x40159b, EndSequence: true},
 	}
+	files := [][]*LineFile{{nil, file1H, file1C}, {nil, file2C}}
 
-	testLineTable(t, want, peData(t, "testdata/line-gcc-win.bin"))
+	testLineTable(t, want, files, peData(t, "testdata/line-gcc-win.bin"))
 }
 
 func TestLineELFClang(t *testing.T) {
@@ -110,8 +112,9 @@ func TestLineELFClang(t *testing.T) {
 		{Address: 0x4005a7, File: file2C, Line: 6, IsStmt: true},
 		{Address: 0x4005b0, EndSequence: true},
 	}
+	files := [][]*LineFile{{nil, file1C, file1H}, {nil, file2C}}
 
-	testLineTable(t, want, elfData(t, "testdata/line-clang.elf"))
+	testLineTable(t, want, files, elfData(t, "testdata/line-clang.elf"))
 }
 
 func TestLineSeek(t *testing.T) {
@@ -190,7 +193,7 @@ func TestLineSeek(t *testing.T) {
 	}
 }
 
-func testLineTable(t *testing.T, want []LineEntry, d *Data) {
+func testLineTable(t *testing.T, want []LineEntry, files [][]*LineFile, d *Data) {
 	// Get line table from d.
 	var got []LineEntry
 	dr := d.Reader()
@@ -207,6 +210,12 @@ func testLineTable(t *testing.T, want []LineEntry, d *Data) {
 			continue
 		}
 
+		// Ignore system compilation units (this happens in
+		// the Windows binary). We'll still decode the line
+		// table, but won't check it.
+		name := ent.Val(AttrName).(string)
+		ignore := strings.HasPrefix(name, "C:/crossdev/") || strings.HasPrefix(name, "../../")
+
 		// Decode CU's line table.
 		lr, err := d.LineReader(ent)
 		if err != nil {
@@ -225,12 +234,23 @@ func testLineTable(t *testing.T, want []LineEntry, d *Data) {
 				t.Fatal("lr.Next:", err)
 			}
 			// Ignore sources from the Windows build environment.
-			if strings.HasPrefix(line.File.Name, "C:\\crossdev\\") ||
-				strings.HasPrefix(line.File.Name, "C:/crossdev/") {
+			if ignore {
 				continue
 			}
 			got = append(got, line)
 		}
+
+		// Check file table.
+		if !ignore {
+			if !compareFiles(files[0], lr.Files()) {
+				t.Log("File tables do not match. Got:")
+				dumpFiles(t, lr.Files())
+				t.Log("Want:")
+				dumpFiles(t, files[0])
+				t.Fail()
+			}
+			files = files[1:]
+		}
 	}
 
 	// Compare line tables.
@@ -243,6 +263,32 @@ func testLineTable(t *testing.T, want []LineEntry, d *Data) {
 	}
 }
 
+func compareFiles(a, b []*LineFile) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] == nil && b[i] == nil {
+			continue
+		}
+		if a[i] != nil && b[i] != nil && a[i].Name == b[i].Name {
+			continue
+		}
+		return false
+	}
+	return true
+}
+
+func dumpFiles(t *testing.T, files []*LineFile) {
+	for i, f := range files {
+		name := "<nil>"
+		if f != nil {
+			name = f.Name
+		}
+		t.Logf("  %d %s", i, name)
+	}
+}
+
 func compareLines(a, b []LineEntry) bool {
 	if len(a) != len(b) {
 		return false