From 8c83177441405ace08650d9d36f76311009c2ed3 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Mon, 2 Nov 2020 17:35:51 -0700 Subject: Introduce DWARF abbrev cache 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. --- gdb/dwarf2/abbrev-cache.h | 58 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 gdb/dwarf2/abbrev-cache.h (limited to 'gdb/dwarf2/abbrev-cache.h') diff --git a/gdb/dwarf2/abbrev-cache.h b/gdb/dwarf2/abbrev-cache.h new file mode 100644 index 0000000..7af28cd --- /dev/null +++ b/gdb/dwarf2/abbrev-cache.h @@ -0,0 +1,58 @@ +/* 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 . */ + +#ifndef GDB_DWARF2_ABBREV_CACHE_H +#define GDB_DWARF2_ABBREV_CACHE_H + +#include "dwarf2/abbrev.h" +#include +#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 */ -- cgit v1.1