Re: Performance regression (12x): Re: RFC: add relative file name handling for linespecs

[Tom Tromey <tromey at redhat dot com>]

>>>>> "Jan" == Jan Kratochvil <jan.kratochvil@redhat.com> writes:

Jan> I have noticed nightly regression testing to start randomly timing
Jan> out a lot for gdb.ada/* testcases, narrowed it down to this
Jan> check-in.

I looked into this.

I still don't know why my patch exposed this problem, but I don't think
it is actually particular to my patch -- instead, I think it is a latent
bug that the patch exposed.

Profiling gdb on gdb.ada/tasks.exp showed:

 time   seconds   seconds    calls  ms/call  ms/call  name    
 60.67      3.07     3.07 80168399     0.00     0.00  advance_wild_match
  9.49      3.55     0.48  1797312     0.00     0.00  match_partial_symbol
  8.50      3.98     0.43 22218321     0.00     0.00  wild_match
[...]

I tracked this down to ada_iterate_over_symbols calling
ada_lookup_symbol_list.  The former expects to iterate upwards starting
from a given block; but the latter will search all top-level blocks of
all objfiles if no local symbol matches.  This means we are doing an N^2
search, because linespec is also doing this sort of iteration.

This fix seems to fix the issue.  The resulting gdb is still a bit
slower than the status quo ante, but not absurdly so.  The profile now
looks like:

 11.11      0.03     0.03    40318     0.00     0.00  d_demangle
  7.41      0.05     0.02   424963     0.00     0.00  advance_wild_match
  7.41      0.07     0.02   351053     0.00     0.00  hash_continue
[...]


Built and regtested on x86-64 Fedora 15.

Joel, is this ok with you?

Tom

2012-01-31  Tom Tromey  <tromey@redhat.com>

	* ada-lang.c (ada_lookup_symbol_list_full): New function, from
	ada_lookup_symbol_list.  Add 'full_search' argument.
	(ada_lookup_symbol_list): Rewrite in terms of
	ada_lookup_symbol_list_full.
	(ada_iterate_over_symbols): Use ada_lookup_symbol_list_full.

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 55e318f..089f666 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -4979,16 +4979,18 @@ add_nonlocal_symbols (struct obstack *obstackp, const char *name,
    the next call of ada_lookup_symbol_list.  Any non-function/non-enumeral 
    symbol match within the nest of blocks whose innermost member is BLOCK0,
    is the one match returned (no other matches in that or
-     enclosing blocks is returned).  If there are any matches in or
-   surrounding BLOCK0, then these alone are returned.  Otherwise, the
-   search extends to global and file-scope (static) symbol tables.
+   enclosing blocks is returned).  If there are any matches in or
+   surrounding BLOCK0, then these alone are returned.  Otherwise, if
+   FULL_SEARCH is non-zero, then the search extends to global and
+   file-scope (static) symbol tables.
    Names prefixed with "standard__" are handled specially: "standard__" 
    is first stripped off, and only static and global symbols are searched.  */
 
-int
-ada_lookup_symbol_list (const char *name0, const struct block *block0,
-                        domain_enum namespace,
-                        struct ada_symbol_info **results)
+static int
+ada_lookup_symbol_list_full (const char *name0, const struct block *block0,
+			     domain_enum namespace,
+			     struct ada_symbol_info **results,
+			     int full_search)
 {
   struct symbol *sym;
   struct block *block;
@@ -5026,7 +5028,7 @@ ada_lookup_symbol_list (const char *name0, const struct block *block0,
 
   ada_add_local_symbols (&symbol_list_obstack, name, block, namespace,
                          wild_match);
-  if (num_defns_collected (&symbol_list_obstack) > 0)
+  if (num_defns_collected (&symbol_list_obstack) > 0 || !full_search)
     goto done;
 
   /* No non-global symbols found.  Check our cache to see if we have
@@ -5070,6 +5072,17 @@ done:
   return ndefns;
 }
 
+/* A wrapper for ada_lookup_symbol_list_full that sets
+   FULL_SEARCH=1.  */
+
+int
+ada_lookup_symbol_list (const char *name0, const struct block *block0,
+			domain_enum namespace,
+			struct ada_symbol_info **results)
+{
+  return ada_lookup_symbol_list_full (name0, block0, namespace, results, 1);
+}
+
 /* If NAME is the name of an entity, return a string that should
    be used to look that entity up in Ada units.  This string should
    be deallocated after use using xfree.
@@ -5106,7 +5119,7 @@ ada_iterate_over_symbols (const struct block *block,
   int ndefs, i;
   struct ada_symbol_info *results;
 
-  ndefs = ada_lookup_symbol_list (name, block, domain, &results);
+  ndefs = ada_lookup_symbol_list_full (name, block, domain, &results, 0);
   for (i = 0; i < ndefs; ++i)
     {
       if (! (*callback) (results[i].sym, data))