invoke.texi: Clarify that most optimizations are not enabled without -O.

2009-10-15  Alexander Monakov  <amonakov@ispras.ru>

	* doc/invoke.texi: Clarify that most optimizations are not enabled
	without -O.

From-SVN: r152852

gcc/ChangeLog

+2009-10-15  Alexander Monakov  <amonakov@ispras.ru>
+
+	* doc/invoke.texi: Clarify that most optimizations are not enabled
+	without -O.
+
 2009-10-15  Richard Guenther  <rguenther@suse.de>
 
 	PR lto/41668

gcc/doc/invoke.texi

@@ -5628,6 +5628,9 @@ each of them.
 Not all optimizations are controlled directly by a flag.  Only
 optimizations that have a flag are listed in this section.
 
+Most of the optimizations are not enabled if a @option{-O} level is not set on
+the command line, even if individual optimization flags are specified.
+
 Depending on the target and how GCC was configured, a slightly different
 set of optimizations may be enabled at each @option{-O} level than
 those listed here.  You can invoke GCC with @samp{-Q --help=optimizers}