From e99f9db0f5211455ca4256e8db9d9081967d255e Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Mon, 10 Jun 2019 20:05:04 +0200 Subject: [PATCH] [gdb/symtab] Fix symbol loading performance regression The commit "[gdb/symtab] Fix language of duplicate static minimal symbol" introduces a performance regression, when loading a cc1 executable build with -O0 -g and gcc 7.4.0. The performance regression, measured in 'real' time is about 175%. The slower execution comes from the fact that the fix in symbol_set_names makes the call to symbol_find_demangled_name unconditional. Fix this by reverting the commit, and redoing the fix as follows. Recapturing the original problem, the first time symbol_set_names is called with gsymbol.language == lang_auto and linkage_name == "_ZL3foov", the name is not present in the per_bfd->demangled_names_hash hash table, so symbol_find_demangled_name is called to demangle the name, after which the mangled/demangled pair is added to the hashtable. The call to symbol_find_demangled_name also sets gsymbol.language to lang_cplus. The second time symbol_set_names is called with gsymbol.language == lang_auto and linkage_name == "_ZL3foov", the name is present in the hash table, so the demangled name from the hash table is used. However, the language of the symbol remains lang_auto. Fix this by adding a field language in struct demangled_name_entry, and using the field in symbol_set_names to set the language of gsymbol, if necessary. Tested on x86_64-linux. gdb/ChangeLog: 2019-06-10 Tom de Vries PR symtab/24545 * symtab.c (struct demangled_name_entry): Add language field. (symbol_set_names): Revert "[gdb/symtab] Fix language of duplicate static minimal symbol". Set and use language field. --- gdb/ChangeLog | 7 +++++++ gdb/symtab.c | 15 +++++++++------ 2 files changed, 16 insertions(+), 6 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index d539e813f6..84b3d68051 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,10 @@ +2019-06-10 Tom de Vries + + PR symtab/24545 + * symtab.c (struct demangled_name_entry): Add language field. + (symbol_set_names): Revert "[gdb/symtab] Fix language of duplicate + static minimal symbol". Set and use language field. + 2019-06-10 Tom Tromey * ada-lang.c (_initialize_ada_language): Update help text. diff --git a/gdb/symtab.c b/gdb/symtab.c index 130d5cd48f..4920d94a24 100644 --- a/gdb/symtab.c +++ b/gdb/symtab.c @@ -713,6 +713,7 @@ symbol_set_language (struct general_symbol_info *gsymbol, struct demangled_name_entry { const char *mangled; + ENUM_BITFIELD(language) language : LANGUAGE_BITS; char demangled[1]; }; @@ -853,11 +854,6 @@ symbol_set_names (struct general_symbol_info *gsymbol, else linkage_name_copy = linkage_name; - /* Set the symbol language. */ - char *demangled_name_ptr - = symbol_find_demangled_name (gsymbol, linkage_name_copy); - gdb::unique_xmalloc_ptr demangled_name (demangled_name_ptr); - entry.mangled = linkage_name_copy; slot = ((struct demangled_name_entry **) htab_find_slot (per_bfd->demangled_names_hash.get (), @@ -870,6 +866,9 @@ symbol_set_names (struct general_symbol_info *gsymbol, || (gsymbol->language == language_go && (*slot)->demangled[0] == '\0')) { + char *demangled_name_ptr + = symbol_find_demangled_name (gsymbol, linkage_name_copy); + gdb::unique_xmalloc_ptr demangled_name (demangled_name_ptr); int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0; /* Suppose we have demangled_name==NULL, copy_name==0, and @@ -906,12 +905,16 @@ symbol_set_names (struct general_symbol_info *gsymbol, strcpy (mangled_ptr, linkage_name_copy); (*slot)->mangled = mangled_ptr; } + (*slot)->language = gsymbol->language; if (demangled_name != NULL) - strcpy ((*slot)->demangled, demangled_name.get()); + strcpy ((*slot)->demangled, demangled_name.get ()); else (*slot)->demangled[0] = '\0'; } + else if (gsymbol->language == language_unknown + || gsymbol->language == language_auto) + gsymbol->language = (*slot)->language; gsymbol->name = (*slot)->mangled; if ((*slot)->demangled[0] != '\0') -- 2.34.1