The replacement for the DWARF psymbol reader works in a somewhat
different way. The current reader reads and stores all the DIEs that
might be interesting. Then, if it is missing a DIE, it re-scans the
CU and reads them all. This approach is used for both intra- and
inter-CU references.
I instrumented the partial DIE hash to see how frequently it was used:
[ 0] ->
1538165
[ 1] -> 4912
[ 2] -> 96102
[ 3] -> 175
[ 4] -> 244
That is, most DIEs are never used, and some are looked up twice -- but
this is just an artifact of the implementation of
partial_die_info::fixup, which may do two lookups.
Based on this, the new implementation doesn't try to store any DIEs,
but instead just re-scans them on demand. In order to do this,
though, it is convenient to have a cache of DWARF abbrevs. This way,
if a second CU is needed to resolve an inter-CU reference, the abbrevs
for that CU need only be computed a single time.
displaced-stepping.c \
dummy-frame.c \
dwarf2/abbrev.c \
+ dwarf2/abbrev-cache.c \
dwarf2/attribute.c \
dwarf2/comp-unit-head.c \
dwarf2/cu.c \
--- /dev/null
+/* DWARF 2 abbrev table cache
+
+ Copyright (C) 2022 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include "defs.h"
+#include "dwarf2/read.h"
+#include "dwarf2/abbrev-cache.h"
+
+/* Hash function for an abbrev table. */
+
+hashval_t
+abbrev_cache::hash_table (const void *item)
+{
+ const struct abbrev_table *table = (const struct abbrev_table *) item;
+ return to_underlying (table->sect_off);
+}
+
+/* Comparison function for abbrev table. */
+
+int
+abbrev_cache::eq_table (const void *lhs, const void *rhs)
+{
+ const struct abbrev_table *l_table = (const struct abbrev_table *) lhs;
+ const search_key *key = (const search_key *) rhs;
+ return (l_table->section == key->section
+ && l_table->sect_off == key->offset);
+}
+
+abbrev_cache::abbrev_cache ()
+ : m_tables (htab_create_alloc (20, hash_table, eq_table,
+ htab_delete_entry<abbrev_table>,
+ xcalloc, xfree))
+{
+}
+
+void
+abbrev_cache::add (abbrev_table_up table)
+{
+ /* We allow this as a convenience to the caller. */
+ if (table == nullptr)
+ return;
+
+ search_key key = { table->section, table->sect_off };
+ void **slot = htab_find_slot_with_hash (m_tables.get (), &key,
+ to_underlying (table->sect_off),
+ INSERT);
+ /* If this one already existed, then it should have been reused. */
+ gdb_assert (*slot == nullptr);
+ *slot = (void *) table.release ();
+}
--- /dev/null
+/* DWARF abbrev table cache
+
+ Copyright (C) 2022 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef GDB_DWARF2_ABBREV_CACHE_H
+#define GDB_DWARF2_ABBREV_CACHE_H
+
+#include "dwarf2/abbrev.h"
+#include <unordered_set>
+#include "gdbtypes.h"
+
+class abbrev_cache
+{
+public:
+ abbrev_cache ();
+ DISABLE_COPY_AND_ASSIGN (abbrev_cache);
+
+ abbrev_table *find (struct dwarf2_section_info *section, sect_offset offset)
+ {
+ search_key key = { section, offset };
+
+ return (abbrev_table *) htab_find_with_hash (m_tables.get (), &key,
+ to_underlying (offset));
+ }
+
+ void add (abbrev_table_up table);
+
+private:
+
+ static hashval_t hash_table (const void *item);
+ static int eq_table (const void *lhs, const void *rhs);
+
+ struct search_key
+ {
+ struct dwarf2_section_info *section;
+ sect_offset offset;
+ };
+
+ /* Hash table of abbrev tables. */
+ htab_up m_tables;
+};
+
+#endif /* GDB_DWARF2_ABBREV_CACHE_H */
dies from a section we read in all abbreviations and install them
in a hash table. */
-abbrev_table::abbrev_table (sect_offset off)
+abbrev_table::abbrev_table (sect_offset off, struct dwarf2_section_info *sect)
: sect_off (off),
+ section (sect),
m_abbrevs (htab_create_alloc (20, hash_abbrev, eq_abbrev,
nullptr, xcalloc, xfree))
{
const gdb_byte *abbrev_ptr;
struct abbrev_info *cur_abbrev;
- abbrev_table_up abbrev_table (new struct abbrev_table (sect_off));
+ abbrev_table_up abbrev_table (new struct abbrev_table (sect_off, section));
struct obstack *obstack = &abbrev_table->m_abbrev_obstack;
/* Caller must ensure this. */
This is used as a sanity check when the table is used. */
const sect_offset sect_off;
+ struct dwarf2_section_info *section;
+
private:
- explicit abbrev_table (sect_offset off);
+ abbrev_table (sect_offset off, struct dwarf2_section_info *sect);
DISABLE_COPY_AND_ASSIGN (abbrev_table);
projects / binutils-gdb.git / commitdiff