diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 43af966f1f7..5cd40fa896c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-01-12  Richard Guenther  <rguenther@suse.de>
+
+	PR other/46946
+	* doc/invoke.texi (ffast-math): Document it is turned on
+	with -Ofast.
+
 2011-01-12  Jan Hubicka  <jh@suse.cz>
 
 	PR tree-optimization/47233
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 800c592d07d..e5ba12cb041 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -7792,10 +7792,10 @@ Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations},
 
 This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
 
-This option is not turned on by any @option{-O} option since
-it can result in incorrect output for programs which depend on
-an exact implementation of IEEE or ISO rules/specifications for
-math functions. It may, however, yield faster code for programs
+This option is not turned on by any @option{-O} option besides
+@option{-Ofast} since it can result in incorrect output for programs
+which depend on an exact implementation of IEEE or ISO rules/specifications
+for math functions. It may, however, yield faster code for programs
 that do not require the guarantees of these specifications.
 
 @item -fno-math-errno