Re: [PATCH 08/14] Remove symtab links from dwarf2_psymtab and dwarf2_per_cu_quick_data

Luis Machado
2020-02-18T11:50:18Z

A comment below...

On 2/15/20 1:54 PM, Tom Tromey wrote:
> This removes the links from dwarf2_psymtab and
> dwarf2_per_cu_quick_data to the compunit_symtab. Now, the DWARF code
> uses the index in these objects to find the corresponding symtab in
> the "unshared" object.
>
> 2020-02-15 Tom Tromey <tom@tromey.com>
>
> * dwarf2/read.h (struct dwarf2_unshareable) <symtabs>: New
> member.
> (struct dwarf2_psymtab): Derive from partial_symtab.
> <readin_p, get_compunit_symtab>: Declare methods.
> * dwarf2/read.c (struct dwarf2_per_cu_quick_data)
> <compunit_symtab>: Remove.
> (dw2_do_instantiate_symtab, dw2_instantiate_symtab)
> (dw2_map_expand_apply, dw2_map_symtabs_matching_filename)
> (dw2_symtab_iter_next, dw2_print_stats)
> (dw2_expand_symtabs_with_fullname)
> (dw2_expand_symtabs_matching_one)
> (dw_expand_symtabs_matching_file_matcher)
> (dw2_find_pc_sect_compunit_symtab, dw2_map_symbol_filenames)
> (dw2_debug_names_iterator::next, does)
> (fill_in_sig_entry_from_dwo_entry, dwarf2_psymtab::read_symtab)
> (process_queue, dwarf2_psymtab::expand_psymtab): Update.
> (dwarf2_psymtab::readin_p, dwarf2_psymtab::get_compunit_symtab):
> New methods.
> (get_compunit_symtab, process_full_comp_unit)
> (process_full_type_unit): Update.
> (dwarf2_build_psymtabs): Resize the symtabs vector.
> (dwarf2_resize_unshareable): New function.
> (dwarf2_initialize_objfile): Call dwarf2_resize_unshareable.
> ---
> gdb/ChangeLog | 26 +++++++
> gdb/dwarf2/read.c | 194 +++++++++++++++++++++++++++++++---------------
> gdb/dwarf2/read.h | 14 +++-
> 3 files changed, 170 insertions(+), 64 deletions(-)
>
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 281d39ad271..44fdb070e49 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -2205,10 +2205,6 @@ struct dwarf2_per_cu_quick_data
> NOTE: This points into dwarf2_per_objfile->quick_file_names_table. */
> struct quick_file_names *file_names;
>
> - /* The corresponding symbol table. This is NULL if symbols for this
> - CU have not yet been read. */
> - struct compunit_symtab *compunit_symtab;
> -
> /* A temporary mark bit used when iterating over all CUs in
> expand_symtabs_matching. */
> unsigned int mark : 1;
> @@ -2332,9 +2328,9 @@ dw2_do_instantiate_symtab (struct dwarf2_per_cu_data *per_cu, bool skip_partial)
> with the dwarf queue empty. */
> dwarf2_queue_guard q_guard (dwarf2_per_objfile);
>
> - if (dwarf2_per_objfile->using_index
> - ? per_cu->v.quick->compunit_symtab == NULL
> - : (per_cu->v.psymtab == NULL || !per_cu->v.psymtab->readin))
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (!symtab.has_value ())

I noticed the above sequence gets repeated a lot throughout the code.
Can we turn it into a function/method and reduce the duplication?

There are other sequences that get repeated, but not as often.

> {
> queue_comp_unit (per_cu, language_minimal);
> load_cu (per_cu, skip_partial);
> @@ -2369,7 +2365,10 @@ dw2_instantiate_symtab (struct dwarf2_per_cu_data *per_cu, bool skip_partial)
> struct dwarf2_per_objfile *dwarf2_per_objfile = per_cu->dwarf2_per_objfile;
>
> gdb_assert (dwarf2_per_objfile->using_index);
> - if (!per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> +
> + if (!symtab.has_value ())
> {
> free_cached_comp_units freer (dwarf2_per_objfile);
> scoped_restore decrementer = increment_reading_symtab ();
> @@ -2377,7 +2376,7 @@ dw2_instantiate_symtab (struct dwarf2_per_cu_data *per_cu, bool skip_partial)
> process_cu_includes (dwarf2_per_objfile);
> }
>
> - return per_cu->v.quick->compunit_symtab;
> + return *symtab;
> }
>
> /* See declaration. */
> @@ -3289,7 +3288,11 @@ dw2_map_expand_apply (struct objfile *objfile,
> struct compunit_symtab *last_made = objfile->compunit_symtabs;
>
> /* Don't visit already-expanded CUs. */
> - if (per_cu->v.quick->compunit_symtab)
> + struct dwarf2_per_objfile *dwarf2_per_objfile
> + = get_dwarf2_per_objfile (objfile);
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> return 0;
>
> /* This may expand more than one symtab, and we want to iterate over
> @@ -3317,7 +3320,9 @@ dw2_map_symtabs_matching_filename
> for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->all_comp_units)
> {
> /* We only need to look at symtabs not already expanded. */
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> continue;
>
> quick_file_names *file_data = dw2_get_file_names (per_cu);
> @@ -3458,7 +3463,9 @@ dw2_symtab_iter_next (struct dw2_symtab_iterator *iter)
> dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (cu_index);
>
> /* Skip if already read in. */
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> continue;
>
> /* Check static vs global. */
> @@ -3573,7 +3580,9 @@ dw2_print_stats (struct objfile *objfile)
> {
> dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
>
> - if (!per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (!symtab.has_value ())
> ++count;
> }
> printf_filtered (_(" Number of read CUs: %d\n"), total - count);
> @@ -3656,7 +3665,9 @@ dw2_expand_symtabs_with_fullname (struct objfile *objfile,
> for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->all_comp_units)
> {
> /* We only need to look at symtabs not already expanded. */
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> continue;
>
> quick_file_names *file_data = dw2_get_file_names (per_cu);
> @@ -4455,15 +4466,19 @@ dw2_expand_symtabs_matching_one
> {
> if (file_matcher == NULL || per_cu->v.quick->mark)
> {
> - bool symtab_was_null
> - = (per_cu->v.quick->compunit_symtab == NULL);
> + struct dwarf2_per_objfile *dwarf2_per_objfile
> + = per_cu->dwarf2_per_objfile;
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + bool symtab_was_null = !symtab.has_value () || *symtab == nullptr;
>
> dw2_instantiate_symtab (per_cu, false);
>
> if (expansion_notify != NULL
> && symtab_was_null
> - && per_cu->v.quick->compunit_symtab != NULL)
> - expansion_notify (per_cu->v.quick->compunit_symtab);
> + && symtab.has_value ()
> + && *symtab != nullptr)
> + expansion_notify (*symtab);
> }
> }
>
> @@ -4583,7 +4598,9 @@ dw_expand_symtabs_matching_file_matcher
> per_cu->v.quick->mark = 0;
>
> /* We only need to look at symtabs not already expanded. */
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> continue;
>
> quick_file_names *file_data = dw2_get_file_names (per_cu);
> @@ -4708,7 +4725,11 @@ dw2_find_pc_sect_compunit_symtab (struct objfile *objfile,
> if (!data)
> return NULL;
>
> - if (warn_if_readin && data->v.quick->compunit_symtab)
> + struct dwarf2_per_objfile *dwarf2_per_objfile
> + = get_dwarf2_per_objfile (objfile);
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[data->index];
> + if (warn_if_readin && symtab.has_value ())
> warning (_("(Internal error: pc %s in read in CU, but not in symtab.)"),
> paddress (get_objfile_arch (objfile), pc));
>
> @@ -4741,7 +4762,9 @@ dw2_map_symbol_filenames (struct objfile *objfile, symbol_filename_ftype *fun,
>
> for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->all_comp_units)
> {
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> {
> void **slot = htab_find_slot (visited.get (),
> per_cu->v.quick->file_names,
> @@ -4754,7 +4777,9 @@ dw2_map_symbol_filenames (struct objfile *objfile, symbol_filename_ftype *fun,
> for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->all_comp_units)
> {
> /* We only need to look at symtabs not already expanded. */
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> continue;
>
> quick_file_names *file_data = dw2_get_file_names (per_cu);
> @@ -5386,7 +5411,9 @@ dw2_debug_names_iterator::next ()
> }
>
> /* Skip if already read in. */
> - if (per_cu->v.quick->compunit_symtab)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value ())
> goto again;
>
> /* Check static vs global. */
> @@ -5627,11 +5654,12 @@ dw2_debug_names_map_matching_symbols
> the psymtab code does. */
> for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->all_comp_units)
> {
> - struct compunit_symtab *cust = per_cu->v.quick->compunit_symtab;
> - if (cust != nullptr)
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + if (symtab.has_value () && *symtab != nullptr)
> {
> const struct block *block
> - = BLOCKVECTOR_BLOCK (COMPUNIT_BLOCKVECTOR (cust), block_kind);
> + = BLOCKVECTOR_BLOCK (COMPUNIT_BLOCKVECTOR (*symtab), block_kind);
> if (!iterate_over_symbols_terminated (block, name,
> domain, callback))
> break;
> @@ -5748,6 +5776,15 @@ get_gdb_index_contents_from_cache_dwz (objfile *obj, dwz_file *dwz)
> return global_index_cache.lookup_gdb_index (build_id, &dwz->index_cache_res);
> }
>
> +/* Make sure we have space for the compunit_symtabs we may need. */
> +
> +static void
> +dwarf2_resize_unshareable (dwarf2_per_objfile *dwarf2_per_objfile)
> +{
> + dwarf2_per_objfile->unshareable->symtabs.resize
> + (dwarf2_per_objfile->num_psymtabs);
> +}
> +
> /* See symfile.h. */
>
> bool
> @@ -5768,6 +5805,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
> dwarf2_per_objfile->quick_file_names_table
> = create_quick_file_names_table
> (dwarf2_per_objfile->all_comp_units.size ());
> + dwarf2_resize_unshareable (dwarf2_per_objfile);
>
> for (int i = 0; i < (dwarf2_per_objfile->all_comp_units.size ()
> + dwarf2_per_objfile->all_type_units.size ()); ++i)
> @@ -5788,6 +5826,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
> if (dwarf2_read_debug_names (dwarf2_per_objfile))
> {
> *index_kind = dw_index_kind::DEBUG_NAMES;
> + dwarf2_resize_unshareable (dwarf2_per_objfile);
> return true;
> }
>
> @@ -5796,6 +5835,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
> get_gdb_index_contents_from_section<dwz_file>))
> {
> *index_kind = dw_index_kind::GDB_INDEX;
> + dwarf2_resize_unshareable (dwarf2_per_objfile);
> return true;
> }
>
> @@ -5806,6 +5846,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
> {
> global_index_cache.hit ();
> *index_kind = dw_index_kind::GDB_INDEX;
> + dwarf2_resize_unshareable (dwarf2_per_objfile);
> return true;
> }
>
> @@ -5834,6 +5875,8 @@ dwarf2_build_psymtabs (struct objfile *objfile)
> dwarf2_build_psymtabs_hard (dwarf2_per_objfile);
> psymtabs.keep ();
>
> + dwarf2_resize_unshareable (dwarf2_per_objfile);
> +
> /* (maybe) store an index in the cache. */
> global_index_cache.store (dwarf2_per_objfile);
> }
> @@ -6259,7 +6302,7 @@ fill_in_sig_entry_from_dwo_entry (struct dwarf2_per_objfile *dwarf2_per_objfile,
> if (dwarf2_per_objfile->using_index)
> {
> gdb_assert (sig_entry->per_cu.v.quick != NULL);
> - gdb_assert (sig_entry->per_cu.v.quick->compunit_symtab == NULL);
> + gdb_assert (!dwarf2_per_objfile->unshareable->symtabs[sig_entry->per_cu.index].has_value ());
> }
> else
> gdb_assert (sig_entry->per_cu.v.psymtab == NULL);
> @@ -8700,7 +8743,10 @@ dwarf2_psymtab::read_symtab (struct objfile *objfile)
> struct dwarf2_per_objfile *dwarf2_per_objfile
> = get_dwarf2_per_objfile (objfile);
>
> - gdb_assert (!readin);
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu_data->index];
> + gdb_assert (!symtab.has_value ());
> +
> /* If this psymtab is constructed from a debug-only objfile, the
> has_section_at_zero flag will not necessarily be correct. We
> can get the correct value for this flag by looking at the data
> @@ -8796,9 +8842,9 @@ process_queue (struct dwarf2_per_objfile *dwarf2_per_objfile)
> {
> dwarf2_queue_item &item = dwarf2_per_objfile->queue.front ();
>
> - if ((dwarf2_per_objfile->using_index
> - ? !item.per_cu->v.quick->compunit_symtab
> - : (item.per_cu->v.psymtab && !item.per_cu->v.psymtab->readin))
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[item.per_cu->index];
> + if (!symtab.has_value ()
> /* Skip dummy CUs. */
> && item.per_cu->cu != NULL)
> {
> @@ -8853,24 +8899,57 @@ process_queue (struct dwarf2_per_objfile *dwarf2_per_objfile)
> void
> dwarf2_psymtab::expand_psymtab (struct objfile *objfile)
> {
> - struct dwarf2_per_cu_data *per_cu;
> -
> - if (readin)
> - return;
> -
> - read_dependencies (objfile);
> -
> - per_cu = per_cu_data;
> + struct dwarf2_per_objfile *dwarf2_per_objfile
> + = get_dwarf2_per_objfile (objfile);
>
> - if (per_cu == NULL)
> + if (per_cu_data == NULL)
> {
> /* It's an include file, no symbols to read for it.
> Everything is in the parent symtab. */
> - readin = true;
> return;
> }
>
> - dw2_do_instantiate_symtab (per_cu, false);
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu_data->index];
> +
> + if (symtab.has_value ())
> + return;
> +
> + read_dependencies (objfile);
> +
> + dw2_do_instantiate_symtab (per_cu_data, false);
> +}
> +
> +/* See psympriv.h. */
> +
> +bool
> +dwarf2_psymtab::readin_p (struct objfile *objfile) const
> +{
> + if (per_cu_data == nullptr)
> + return true;
> +
> + dwarf2_per_objfile *dwarf2_per_objfile
> + = get_dwarf2_per_objfile (objfile);
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu_data->index];
> + return symtab.has_value ();
> +}
> +
> +/* See psympriv.h. */
> +
> +compunit_symtab *
> +dwarf2_psymtab::get_compunit_symtab (struct objfile *objfile) const
> +{
> + if (per_cu_data == nullptr)
> + return nullptr;
> +
> + dwarf2_per_objfile *dwarf2_per_objfile
> + = get_dwarf2_per_objfile (objfile);
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu_data->index];
> + if (!symtab.has_value ())
> + return nullptr;
> + return *symtab;
> }
>
> /* Trivial hash function for die_info: the hash value of a DIE
> @@ -9413,9 +9492,12 @@ rust_union_quirks (struct dwarf2_cu *cu)
> static struct compunit_symtab *
> get_compunit_symtab (struct dwarf2_per_cu_data *per_cu)
> {
> - return (per_cu->dwarf2_per_objfile->using_index
> - ? per_cu->v.quick->compunit_symtab
> - : per_cu->v.psymtab->compunit_symtab);
> + struct dwarf2_per_objfile *dwarf2_per_objfile
> + = per_cu->dwarf2_per_objfile;
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + gdb_assert (symtab.has_value ());
> + return *symtab;
> }
>
> /* A helper function for computing the list of all symbol tables
> @@ -9621,14 +9703,9 @@ process_full_comp_unit (struct dwarf2_per_cu_data *per_cu,
> cust->call_site_htab = cu->call_site_htab;
> }
>
> - if (dwarf2_per_objfile->using_index)
> - per_cu->v.quick->compunit_symtab = cust;
> - else
> - {
> - dwarf2_psymtab *pst = per_cu->v.psymtab;
> - pst->compunit_symtab = cust;
> - pst->readin = true;
> - }
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + symtab = cust;
>
> /* Push it for inclusion processing later. */
> dwarf2_per_objfile->just_read_cus.push_back (per_cu);
> @@ -9701,14 +9778,9 @@ process_full_type_unit (struct dwarf2_per_cu_data *per_cu,
> cust = sig_type->type_unit_group->compunit_symtab;
> }
>
> - if (dwarf2_per_objfile->using_index)
> - per_cu->v.quick->compunit_symtab = cust;
> - else
> - {
> - dwarf2_psymtab *pst = per_cu->v.psymtab;
> - pst->compunit_symtab = cust;
> - pst->readin = true;
> - }
> + gdb::optional<compunit_symtab *> &symtab
> + = dwarf2_per_objfile->unshareable->symtabs[per_cu->index];
> + symtab = cust;
>
> /* Not needed any more. */
> cu->reset_builder ();
> diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
> index 5fc7f7f72e5..98d58fb6880 100644
> --- a/gdb/dwarf2/read.h
> +++ b/gdb/dwarf2/read.h
> @@ -82,6 +82,10 @@ struct dwarf2_unshareable
> This is NULL if not allocated yet.
> The mapping is done via (CU/TU + DIE offset) -> type. */
> htab_up die_type_hash;
> +
> + /* Hold the corresponding compunit_symtab for each CU or TU. This
> + is indexed by dwarf2_per_cu_data::index. */
> + std::vector<gdb::optional<compunit_symtab *>> symtabs;
> };
>
> /* Collection of data recorded per objfile.
> @@ -281,22 +285,26 @@ public:
> dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
>
> /* A partial symtab specialized for DWARF. */
> -struct dwarf2_psymtab : public standard_psymtab
> +struct dwarf2_psymtab : public partial_symtab
> {
> dwarf2_psymtab (const char *filename, struct objfile *objfile)
> - : standard_psymtab (filename, objfile)
> + : partial_symtab (filename, objfile)
> {
> }
>
> dwarf2_psymtab (const char *filename, struct objfile *objfile,
> CORE_ADDR addr)
> - : standard_psymtab (filename, objfile, addr)
> + : partial_symtab (filename, objfile, addr)
> {
> }
>
> void read_symtab (struct objfile *) override;
> void expand_psymtab (struct objfile *) override;
>
> + bool readin_p (struct objfile *) const override;
> + struct compunit_symtab *get_compunit_symtab (struct objfile *) const
> + override;
> +
> struct dwarf2_per_cu_data *per_cu_data;
> };
>
>