From ba715d7fe49c8a59660fbd571b935b29eb7cfbdb Mon Sep 17 00:00:00 2001 From: Jan Kratochvil Date: Thu, 4 Dec 2014 08:26:26 +0100 Subject: [PATCH] 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 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 Display all 183904 possibilities? (y or n) n (gdb) p/r var $1 = {static npos = , _M_dataplus = {> = {<__gnu_cxx::new_allocator> = {}, }, _M_p = 0x3a4db073d8 ""}} 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 * 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. --- gdb/ChangeLog | 7 +++++++ gdb/block.c | 25 +++++++++++++++++++++++++ gdb/block.h | 8 ++++++++ gdb/symtab.c | 4 +++- 4 files changed, 43 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 80eb8c9..352d107 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,10 @@ +2014-12-04 Jan Kratochvil + + * 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. + 2014-12-03 Maciej W. Rozycki * tramp-frame.h (tramp_frame): Add `validate' member. diff --git a/gdb/block.c b/gdb/block.c index 597d143..e791c73 100644 --- a/gdb/block.c +++ b/gdb/block.c @@ -746,3 +746,28 @@ block_lookup_symbol (const struct block *block, const char *name, return (sym_found); /* Will be NULL if not found. */ } } + +/* See block.h. */ + +struct symbol * +block_lookup_symbol_primary (const struct block *block, const char *name, + const domain_enum domain) +{ + struct symbol *sym; + struct dict_iterator dict_iter; + + /* Verify BLOCK is STATIC_BLOCK or GLOBAL_BLOCK. */ + gdb_assert (BLOCK_SUPERBLOCK (block) == NULL + || BLOCK_SUPERBLOCK (BLOCK_SUPERBLOCK (block)) == NULL); + + for (sym = dict_iter_name_first (block->dict, name, &dict_iter); + sym != NULL; + sym = dict_iter_name_next (name, &dict_iter)) + { + if (symbol_matches_domain (SYMBOL_LANGUAGE (sym), + SYMBOL_DOMAIN (sym), domain)) + return sym; + } + + return NULL; +} diff --git a/gdb/block.h b/gdb/block.h index bd358d6..409a5c7 100644 --- a/gdb/block.h +++ b/gdb/block.h @@ -276,6 +276,14 @@ 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. */ diff --git a/gdb/symtab.c b/gdb/symtab.c index a52f7c0..d8d8e23 100644 --- a/gdb/symtab.c +++ b/gdb/symtab.c @@ -1585,6 +1585,8 @@ lookup_symbol_in_objfile_symtabs (struct objfile *objfile, int block_index, { struct compunit_symtab *cust; + gdb_assert (block_index == GLOBAL_BLOCK || block_index == STATIC_BLOCK); + ALL_OBJFILE_COMPUNITS (objfile, cust) { const struct blockvector *bv; @@ -1593,7 +1595,7 @@ lookup_symbol_in_objfile_symtabs (struct objfile *objfile, int block_index, bv = COMPUNIT_BLOCKVECTOR (cust); block = BLOCKVECTOR_BLOCK (bv, block_index); - sym = block_lookup_symbol (block, name, domain); + sym = block_lookup_symbol_primary (block, name, domain); if (sym) { block_found = block; -- 2.7.4