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8c83177441
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.
66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
/* DWARF 2 abbrev table cache
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Copyright (C) 2022 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "defs.h"
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#include "dwarf2/read.h"
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#include "dwarf2/abbrev-cache.h"
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/* Hash function for an abbrev table. */
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hashval_t
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abbrev_cache::hash_table (const void *item)
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{
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const struct abbrev_table *table = (const struct abbrev_table *) item;
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return to_underlying (table->sect_off);
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}
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/* Comparison function for abbrev table. */
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int
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abbrev_cache::eq_table (const void *lhs, const void *rhs)
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{
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const struct abbrev_table *l_table = (const struct abbrev_table *) lhs;
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const search_key *key = (const search_key *) rhs;
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return (l_table->section == key->section
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&& l_table->sect_off == key->offset);
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}
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abbrev_cache::abbrev_cache ()
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: m_tables (htab_create_alloc (20, hash_table, eq_table,
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htab_delete_entry<abbrev_table>,
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xcalloc, xfree))
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{
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}
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void
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abbrev_cache::add (abbrev_table_up table)
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{
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/* We allow this as a convenience to the caller. */
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if (table == nullptr)
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return;
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search_key key = { table->section, table->sect_off };
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void **slot = htab_find_slot_with_hash (m_tables.get (), &key,
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to_underlying (table->sect_off),
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INSERT);
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/* If this one already existed, then it should have been reused. */
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gdb_assert (*slot == nullptr);
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*slot = (void *) table.release ();
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}
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