Avoid expensive complaint calls when complaints are disabled

Running perf on "gdb -nx -readnow -batch gdb", I'm seeing a lot of
time (24%.75!) spent in gettext, via complaints.  'perf report -g' shows:

 -   86.23%     0.00%  gdb      gdb                     [.] gdb_main
    - gdb_main
       - 85.60% catch_command_errors
            symbol_file_add_main_adapter
            symbol_file_add_main
            symbol_file_add_main_1
            symbol_file_add
          - symbol_file_add_with_addrs
             - 84.31% dw2_expand_all_symtabs
                - dw2_instantiate_symtab
                   - 83.79% dw2_do_instantiate_symtab
                      - 70.85% process_die
                         - 41.11% dwarf_decode_macros
                            - 41.09% dwarf_decode_macro_bytes
                               - 39.74% dwarf_decode_macro_bytes
   >>>>>>>>>>>>>>>>>>>>>>>        + 24.75% __dcigettext              <<<<<<<
                                  + 7.37% macro_define_object_internal
                                  + 3.16% macro_define_function
                                    0.77% splay_tree_insert
                                  + 0.76% savestring
                                  + 0.58% free
                                    0.53% read_indirect_string_at_offset_from
                                 0.54% macro_define_object_internal
                                 0.51% macro_start_file
                         + 25.57% process_die
                         + 4.07% dwarf_decode_lines
                      + 4.28% compute_delayed_physnames
                      + 3.85% end_symtab_from_static_block
                      + 3.38% load_cu
                      + 1.29% end_symtab_get_static_block
                   + 0.52% do_my_cleanups
             + 1.29% read_symbols
       + 0.54% gdb_init

The problem is that we're always computing the arguments to pass to
complaint, including passing the format strings through gettext, even
when complaints are disabled.  As seen above, gettext can be quite
expensive.

Fix this by wrapping complaint in a macro that skips the real
complaint call when complaints are disabled.

This improves "gdb -nx -readnow -batch gdb" from
 ~11.0s => ~7.8s with -O2 -g3, and
  ~6.0s => ~5.3s with -O2 -g.
w/ gcc 5.3.1, on x86_64, for me.

gdb/ChangeLog:
2017-11-08  Pedro Alves  <palves@redhat.com>

	* complaints.c (stop_whining): Make extern.
	(complaint): Rename to ...
	(complaint_internal): ... this.
	* complaints.h (complaint): Rename to ...
	(complaint_internal): ... this.
	(complaint): Reimplement as macro around complaint_internal.

gdb/testsuite/ChangeLog:
2017-11-08  Pedro Alves  <palves@redhat.com>

	* gdb.gdb/complaints.exp (test_initial_complaints)
	(test_serial_complaints, test_short_complaints): Call
	complaint_internal instead of complaint.

1 files changed, 19 insertions, 4 deletions

diff --git a/gdb/complaints.h b/gdb/complaints.h
index 54c2b18..62885e9 100644
--- a/gdb/complaints.h
+++ b/gdb/complaints.h
@@ -28,10 +28,25 @@ struct complaints;
 /* Predefined categories.  */
 extern struct complaints *symfile_complaints;
 
-/* Register a complaint.  */
-extern void complaint (struct complaints **complaints,
-		       const char *fmt,
-		       ...) ATTRIBUTE_PRINTF (2, 3);
+/* Helper for complaint.  */
+extern void complaint_internal (struct complaints **complaints,
+				const char *fmt, ...)
+  ATTRIBUTE_PRINTF (2, 3);
+
+/* Register a complaint.  This is a macro around complaint_internal to
+   avoid computing complaint's arguments when complaints are disabled.
+   Running FMT via gettext [i.e., _(FMT)] can be quite expensive, for
+   example.  */
+#define complaint(COMPLAINTS, FMT, ...)				\
+  do								\
+    {								\
+      extern int stop_whining;					\
+								\
+      if (stop_whining > 0)					\
+	complaint_internal (COMPLAINTS, FMT, ##__VA_ARGS__);	\
+    }								\
+  while (0)
+
 extern void internal_complaint (struct complaints **complaints,
 				const char *file, int line,
 				const char *fmt,