On Mon, 26 Jul 2021, Bernd Edlinger wrote:
> Ignored functions decls that are compiled at the start of
> the assembly have bogus line numbers until the first .file
> directive, as reported in PR101575.
>
> The work around for this issue is to emit a dummy .file
> directive when the first function is DECL_IGNORED_P, when
> that is not already done, mostly for -fdwarf-4.
I wonder if it makes sense to unconditionally announce the
TU with a .file directive at the beginning. ISTR this is
what we now do with -gdwarf-5.
Note get_AT_string (comp_unit_die (), DW_AT_name) doesn't
work with LTO, you'll get <dummy> then.
Is the dwarf assembler bug reported/fixed? Can you include
a reference please?
Thanks,
Richard.
> 2021-07-24 Bernd Edlinger <bernd.edlin...@hotmail.de>
>
> PR ada/101575
> * dwarf2out.c (dwarf2out_begin_prologue): Move init
> of fde->ignored_debug to dwarf2out_set_ignored_loc.
> (dwarf2out_set_ignored_loc): This is now also called
> when no .loc statement is to be generated, in that case
> we emit a dummy .file statement when needed.
> * final.c (final_start_function_1,
> final_scan_insn_1): Call debug_hooks->set_ignored_loc
> for all DECL_IGNORED_P functions.
> ---
> gcc/dwarf2out.c | 29 +++++++++++++++++++++++++----
> gcc/final.c | 5 ++---
> 2 files changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
> index 884f1e1..8de0d6f 100644
> --- a/gcc/dwarf2out.c
> +++ b/gcc/dwarf2out.c
> @@ -1115,7 +1115,6 @@ dwarf2out_begin_prologue (unsigned int line
> ATTRIBUTE_UNUSED,
> fde->dw_fde_current_label = dup_label;
> fde->in_std_section = (fnsec == text_section
> || (cold_text_section && fnsec == cold_text_section));
> - fde->ignored_debug = DECL_IGNORED_P (current_function_decl);
> in_text_section_p = fnsec == text_section;
>
> /* We only want to output line number information for the genuine dwarf2
> @@ -28546,10 +28545,32 @@ dwarf2out_set_ignored_loc (unsigned int line,
> unsigned int column,
> {
> dw_fde_ref fde = cfun->fde;
>
> - fde->ignored_debug = false;
> - set_cur_line_info_table (function_section (fde->decl));
> + if (filename)
> + {
> + set_cur_line_info_table (function_section (fde->decl));
> +
> + dwarf2out_source_line (line, column, filename, 0, true);
> + }
> + else
> + {
> + fde->ignored_debug = true;
> +
> + /* Work around for PR101575: output a dummy .file directive. */
> + if (in_first_function_p
> + && debug_info_level >= DINFO_LEVEL_TERSE
> + && dwarf_debuginfo_p ()
> +#if defined(HAVE_AS_GDWARF_5_DEBUG_FLAG) &&
> defined(HAVE_AS_WORKING_DWARF_N_FLAG)
> + && dwarf_version <= 4
> +#endif
> + && output_asm_line_debug_info ())
> + {
> + const char *filename0 = get_AT_string (comp_unit_die (), DW_AT_name);
>
> - dwarf2out_source_line (line, column, filename, 0, true);
> + if (filename0 == NULL)
> + filename0 = "<dummy>";
> + maybe_emit_file (lookup_filename (filename0));
> + }
> + }
> }
>
> /* Record the beginning of a new source file. */
> diff --git a/gcc/final.c b/gcc/final.c
> index ac6892d..82a5767 100644
> --- a/gcc/final.c
> +++ b/gcc/final.c
> @@ -1725,7 +1725,7 @@ final_start_function_1 (rtx_insn **firstp, FILE *file,
> int *seen,
> if (!dwarf2_debug_info_emitted_p (current_function_decl))
> dwarf2out_begin_prologue (0, 0, NULL);
>
> - if (DECL_IGNORED_P (current_function_decl) && last_linenum &&
> last_filename)
> + if (DECL_IGNORED_P (current_function_decl))
> debug_hooks->set_ignored_loc (last_linenum, last_columnnum,
> last_filename);
>
> #ifdef LEAF_REG_REMAP
> @@ -2205,8 +2205,7 @@ final_scan_insn_1 (rtx_insn *insn, FILE *file, int
> optimize_p ATTRIBUTE_UNUSED,
> }
> else if (!DECL_IGNORED_P (current_function_decl))
> debug_hooks->switch_text_section ();
> - if (DECL_IGNORED_P (current_function_decl) && last_linenum
> - && last_filename)
> + if (DECL_IGNORED_P (current_function_decl))
> debug_hooks->set_ignored_loc (last_linenum, last_columnnum,
> last_filename);
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
