[gcc r11-8650] Emit .file 0 directive earlier in DWARF 5

[Eric Botcazou <ebotcazou@gcc.gnu.org>]

https://gcc.gnu.org/g:f19b20de1b24d6b53479c6815316a5201b22775d

commit r11-8650-gf19b20de1b24d6b53479c6815316a5201b22775d
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Thu Jun 24 12:55:27 2021 +0200

    Emit .file 0 directive earlier in DWARF 5
    
    When the assembler supports it, the compiler automatically passes --gdwarf-5
    to it, which has an interesting side effect: any assembly instruction prior
    to the first .file directive defines a new line associated with .file 0 in
    the .debug_line section and of course the numbering of these implicit lines
    has nothing to do with that of the source code.  This can be problematic in
    Ada when we do not generate .file/.loc directives for compiled-generated
    functions to avoid too jumpy a debugging experience.
    
    gcc/
            * dwarf2out.c (dwarf2out_assembly_start): Emit .file 0 marker here..
            (dwarf2out_finish): ...instead of here.

Diff:
---
 gcc/dwarf2out.c | 45 ++++++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 7a15debcb48..079b617fd0c 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -29121,6 +29121,30 @@ dwarf2out_assembly_start (void)
       && dwarf2out_do_cfi_asm ()
       && !dwarf2out_do_eh_frame ())
     fprintf (asm_out_file, "\t.cfi_sections\t.debug_frame\n");
+
+#if defined(HAVE_AS_GDWARF_5_DEBUG_FLAG) && defined(HAVE_AS_WORKING_DWARF_N_FLAG)
+  if (output_asm_line_debug_info () && dwarf_version >= 5)
+    {
+      /* When gas outputs DWARF5 .debug_line[_str] then we have to
+	 tell it the comp_dir and main file name for the zero entry
+	 line table.  */
+      const char *comp_dir, *filename0;
+
+      comp_dir = comp_dir_string ();
+      if (comp_dir == NULL)
+	comp_dir = "";
+
+      filename0 = get_AT_string (comp_unit_die (), DW_AT_name);
+      if (filename0 == NULL)
+	filename0 = "";
+
+      fprintf (asm_out_file, "\t.file 0 ");
+      output_quoted_string (asm_out_file, remap_debug_filename (comp_dir));
+      fputc (' ', asm_out_file);
+      output_quoted_string (asm_out_file, remap_debug_filename (filename0));
+      fputc ('\n', asm_out_file);
+    }
+#endif
 }
 
 /* A helper function for dwarf2out_finish called through
@@ -32034,27 +32058,6 @@ dwarf2out_finish (const char *filename)
   ASM_OUTPUT_LABEL (asm_out_file, debug_line_section_label);
   if (! output_asm_line_debug_info ())
     output_line_info (false);
-  else if (asm_outputs_debug_line_str ())
-    {
-      /* When gas outputs DWARF5 .debug_line[_str] then we have to
-	 tell it the comp_dir and main file name for the zero entry
-	 line table.  */
-      const char *comp_dir, *filename0;
-
-      comp_dir = comp_dir_string ();
-      if (comp_dir == NULL)
-	comp_dir = "";
-
-      filename0 = get_AT_string (comp_unit_die (), DW_AT_name);
-      if (filename0 == NULL)
-	filename0 = "";
-
-      fprintf (asm_out_file, "\t.file 0 ");
-      output_quoted_string (asm_out_file, remap_debug_filename (comp_dir));
-      fputc (' ', asm_out_file);
-      output_quoted_string (asm_out_file, remap_debug_filename (filename0));
-      fputc ('\n', asm_out_file);
-    }
 
   if (dwarf_split_debug_info && info_section_emitted)
     {