binutils-gdb/gdb/block.h
Jan Kratochvil ba715d7fe4 Accelerate lookup_symbol_aux_objfile 85x
During debugging I get 10-30 seconds for a response to simple commands like:
	(gdb) print vectorvar.size()
With this patch the performance gets to 1-2 seconds which is somehow
acceptable.  The problem is that dwarf2_gdb_index_functions.lookup_symbol
(quick_symbol_functions::lookup_symbol) may return (and returns) NULL even for
symbols which are present in .gdb_index but which can be found in already
expanded symtab.  But searching in the already expanded symtabs is just too
slow when there are 400000+ expanded symtabs.  There would be needed some
single global hash table for each objfile so that one does not have to iterate
all symtabs.  Which .gdb_index could perfectly serve for, just its
lookup_symbol() would need to return authoritative yes/no answers.

Even after such fix these two simple patches are useful for example for
non-.gdb_index files.

One can reproduce the slugging interactive GDB performance with:
	#include <string>
	using namespace std;
	string var;
	class C {
	public:
	  void m() {}
	};
	int main() {
	  C c;
	  c.m();
	  return 0;
	}
g++ -o slow slow.C -Wall -g $(pkg-config --libs gtkmm-3.0)
gdb ./slow -ex 'b C::m' -ex 'maintenance set per-command space' -ex 'maintenance set per-command symtab' -ex 'maintenance set per-command
time' -ex r
[...]
(gdb) p <tab><tab>
Display all 183904 possibilities? (y or n) n
(gdb) p/r var
$1 = {static npos = <optimized out>, _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No
data fields>}, _M_p = 0x3a4db073d8 <std::string::_Rep::_S_empty_rep_storage+24> ""}}
Command execution time: 20.023000 (cpu), 20.118665 (wall)
                        ^^^^^^^^^
Space used: 927997952 (+0 for this command)

Without DWZ there are X global blocks for X primary symtabs for X CUs of
objfile.  With DWZ there are X+Y global blocks for X+Y primary symtabs for
X+Y CUs where Y are 'DW_TAG_partial_unit's.

For 'DW_TAG_partial_unit's (Ys) their blockvector is usually empty.  But not
always, I have found there typedef symbols, there can IMO be optimized-out
static variables etc.

Neither of the patches should cause any visible behavior change.

gdb/ChangeLog
2014-12-04  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* block.c (block_lookup_symbol_primary): New function.
	* block.h (block_lookup_symbol_primary): New declaration.
	* symtab.c (lookup_symbol_in_objfile_symtabs): Assert BLOCK_INDEX.
	Call block_lookup_symbol_primary.
2014-12-04 08:26:26 +01:00

306 lines
10 KiB
C

/* Code dealing with blocks for GDB.
Copyright (C) 2003-2014 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 BLOCK_H
#define BLOCK_H
#include "dictionary.h"
/* Opaque declarations. */
struct symbol;
struct compunit_symtab;
struct block_namespace_info;
struct using_direct;
struct obstack;
struct addrmap;
/* All of the name-scope contours of the program
are represented by `struct block' objects.
All of these objects are pointed to by the blockvector.
Each block represents one name scope.
Each lexical context has its own block.
The blockvector begins with some special blocks.
The GLOBAL_BLOCK contains all the symbols defined in this compilation
whose scope is the entire program linked together.
The STATIC_BLOCK contains all the symbols whose scope is the
entire compilation excluding other separate compilations.
Blocks starting with the FIRST_LOCAL_BLOCK are not special.
Each block records a range of core addresses for the code that
is in the scope of the block. The STATIC_BLOCK and GLOBAL_BLOCK
give, for the range of code, the entire range of code produced
by the compilation that the symbol segment belongs to.
The blocks appear in the blockvector
in order of increasing starting-address,
and, within that, in order of decreasing ending-address.
This implies that within the body of one function
the blocks appear in the order of a depth-first tree walk. */
struct block
{
/* Addresses in the executable code that are in this block. */
CORE_ADDR startaddr;
CORE_ADDR endaddr;
/* The symbol that names this block, if the block is the body of a
function (real or inlined); otherwise, zero. */
struct symbol *function;
/* The `struct block' for the containing block, or 0 if none.
The superblock of a top-level local block (i.e. a function in the
case of C) is the STATIC_BLOCK. The superblock of the
STATIC_BLOCK is the GLOBAL_BLOCK. */
struct block *superblock;
/* This is used to store the symbols in the block. */
struct dictionary *dict;
/* Used for language-specific info. */
union
{
struct
{
/* Contains information about namespace-related info relevant to
this block: using directives and the current namespace
scope. */
struct block_namespace_info *namespace;
}
cplus_specific;
}
language_specific;
};
/* The global block is singled out so that we can provide a back-link
to the compunit symtab. */
struct global_block
{
/* The block. */
struct block block;
/* This holds a pointer to the compunit symtab holding this block. */
struct compunit_symtab *compunit_symtab;
};
#define BLOCK_START(bl) (bl)->startaddr
#define BLOCK_END(bl) (bl)->endaddr
#define BLOCK_FUNCTION(bl) (bl)->function
#define BLOCK_SUPERBLOCK(bl) (bl)->superblock
#define BLOCK_DICT(bl) (bl)->dict
#define BLOCK_NAMESPACE(bl) (bl)->language_specific.cplus_specific.namespace
struct blockvector
{
/* Number of blocks in the list. */
int nblocks;
/* An address map mapping addresses to blocks in this blockvector.
This pointer is zero if the blocks' start and end addresses are
enough. */
struct addrmap *map;
/* The blocks themselves. */
struct block *block[1];
};
#define BLOCKVECTOR_NBLOCKS(blocklist) (blocklist)->nblocks
#define BLOCKVECTOR_BLOCK(blocklist,n) (blocklist)->block[n]
#define BLOCKVECTOR_MAP(blocklist) ((blocklist)->map)
extern struct symbol *block_linkage_function (const struct block *);
extern struct symbol *block_containing_function (const struct block *);
extern int block_inlined_p (const struct block *block);
extern int contained_in (const struct block *, const struct block *);
extern const struct blockvector *blockvector_for_pc (CORE_ADDR,
const struct block **);
extern const struct blockvector *
blockvector_for_pc_sect (CORE_ADDR, struct obj_section *,
const struct block **, struct compunit_symtab *);
extern int blockvector_contains_pc (const struct blockvector *bv, CORE_ADDR pc);
extern struct call_site *call_site_for_pc (struct gdbarch *gdbarch,
CORE_ADDR pc);
extern const struct block *block_for_pc (CORE_ADDR);
extern const struct block *block_for_pc_sect (CORE_ADDR, struct obj_section *);
extern const char *block_scope (const struct block *block);
extern void block_set_scope (struct block *block, const char *scope,
struct obstack *obstack);
extern struct using_direct *block_using (const struct block *block);
extern void block_set_using (struct block *block,
struct using_direct *using,
struct obstack *obstack);
extern const struct block *block_static_block (const struct block *block);
extern const struct block *block_global_block (const struct block *block);
extern struct block *allocate_block (struct obstack *obstack);
extern struct block *allocate_global_block (struct obstack *obstack);
extern void set_block_compunit_symtab (struct block *,
struct compunit_symtab *);
/* A block iterator. This structure should be treated as though it
were opaque; it is only defined here because we want to support
stack allocation of iterators. */
struct block_iterator
{
/* If we're iterating over a single block, this holds the block.
Otherwise, it holds the canonical compunit. */
union
{
struct compunit_symtab *compunit_symtab;
const struct block *block;
} d;
/* If we're iterating over a single block, this is always -1.
Otherwise, it holds the index of the current "included" symtab in
the canonical symtab (that is, d.symtab->includes[idx]), with -1
meaning the canonical symtab itself. */
int idx;
/* Which block, either static or global, to iterate over. If this
is FIRST_LOCAL_BLOCK, then we are iterating over a single block.
This is used to select which field of 'd' is in use. */
enum block_enum which;
/* The underlying dictionary iterator. */
struct dict_iterator dict_iter;
};
/* Initialize ITERATOR to point at the first symbol in BLOCK, and
return that first symbol, or NULL if BLOCK is empty. */
extern struct symbol *block_iterator_first (const struct block *block,
struct block_iterator *iterator);
/* Advance ITERATOR, and return the next symbol, or NULL if there are
no more symbols. Don't call this if you've previously received
NULL from block_iterator_first or block_iterator_next on this
iteration. */
extern struct symbol *block_iterator_next (struct block_iterator *iterator);
/* Initialize ITERATOR to point at the first symbol in BLOCK whose
SYMBOL_SEARCH_NAME is NAME (as tested using strcmp_iw), and return
that first symbol, or NULL if there are no such symbols. */
extern struct symbol *block_iter_name_first (const struct block *block,
const char *name,
struct block_iterator *iterator);
/* Advance ITERATOR to point at the next symbol in BLOCK whose
SYMBOL_SEARCH_NAME is NAME (as tested using strcmp_iw), or NULL if
there are no more such symbols. Don't call this if you've
previously received NULL from block_iterator_first or
block_iterator_next on this iteration. And don't call it unless
ITERATOR was created by a previous call to block_iter_name_first
with the same NAME. */
extern struct symbol *block_iter_name_next (const char *name,
struct block_iterator *iterator);
/* Initialize ITERATOR to point at the first symbol in BLOCK whose
SYMBOL_SEARCH_NAME is NAME, as tested using COMPARE (which must use
the same conventions as strcmp_iw and be compatible with any
block hashing function), and return that first symbol, or NULL
if there are no such symbols. */
extern struct symbol *block_iter_match_first (const struct block *block,
const char *name,
symbol_compare_ftype *compare,
struct block_iterator *iterator);
/* Advance ITERATOR to point at the next symbol in BLOCK whose
SYMBOL_SEARCH_NAME is NAME, as tested using COMPARE (see
block_iter_match_first), or NULL if there are no more such symbols.
Don't call this if you've previously received NULL from
block_iterator_match_first or block_iterator_match_next on this
iteration. And don't call it unless ITERATOR was created by a
previous call to block_iter_match_first with the same NAME and COMPARE. */
extern struct symbol *block_iter_match_next (const char *name,
symbol_compare_ftype *compare,
struct block_iterator *iterator);
/* Search BLOCK for symbol NAME in DOMAIN. */
extern struct symbol *block_lookup_symbol (const struct block *block,
const char *name,
const domain_enum domain);
/* Search BLOCK for symbol NAME in DOMAIN but only in primary symbol table of
BLOCK. BLOCK must be STATIC_BLOCK or GLOBAL_BLOCK. Function is useful if
one iterates all global/static blocks of an objfile. */
extern struct symbol *block_lookup_symbol_primary (const struct block *block,
const char *name,
const domain_enum domain);
/* Macro to loop through all symbols in BLOCK, in no particular
order. ITER helps keep track of the iteration, and must be a
struct block_iterator. SYM points to the current symbol. */
#define ALL_BLOCK_SYMBOLS(block, iter, sym) \
for ((sym) = block_iterator_first ((block), &(iter)); \
(sym); \
(sym) = block_iterator_next (&(iter)))
/* Macro to loop through all symbols with name NAME in BLOCK,
in no particular order. ITER helps keep track of the iteration, and
must be a struct block_iterator. SYM points to the current symbol. */
#define ALL_BLOCK_SYMBOLS_WITH_NAME(block, name, iter, sym) \
for ((sym) = block_iter_name_first ((block), (name), &(iter)); \
(sym) != NULL; \
(sym) = block_iter_name_next ((name), &(iter)))
#endif /* BLOCK_H */