Update documentation of fndecl_built_in_p.

2018-08-28  Martin Liska  <mliska@suse.cz>

	* tree.h: Update documentation of fndecl_built_in_p
	functions.

From-SVN: r263907

gcc/ChangeLog

+2018-08-28  Martin Liska  <mliska@suse.cz>
+
+	* tree.h: Update documentation of fndecl_built_in_p
+	functions.
+
 2018-08-27  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/87110

gcc/tree.h

@@ -5834,16 +5834,11 @@ type_has_mode_precision_p (const_tree t)
   return known_eq (TYPE_PRECISION (t), GET_MODE_PRECISION (TYPE_MODE (t)));
 }
 
-/* For a FUNCTION_DECL NODE, nonzero means a built in function of a
-   standard library or more generally a built in function that is
-   recognized by optimizers and expanders.
+/* Return true if a FUNCTION_DECL NODE is a GCC built-in function.
 
    Note that it is different from the DECL_IS_BUILTIN accessor.  For
    instance, user declared prototypes of C library functions are not
-   DECL_IS_BUILTIN but may be DECL_BUILT_IN.
-
-   When a NULL argument is pass or tree code of the NODE is not FUNCTION_DECL
-   false is returned.  */
+   DECL_IS_BUILTIN but may be DECL_BUILT_IN.  */
 
 inline bool
 fndecl_built_in_p (const_tree node)
@@ -5851,8 +5846,8 @@ fndecl_built_in_p (const_tree node)
   return (DECL_BUILT_IN_CLASS (node) != NOT_BUILT_IN);
 }
 
-/* For a FUNCTION_DECL NODE, return true when a function is
-   a built-in of class KLASS.  */
+/* Return true if a FUNCTION_DECL NODE is a GCC built-in function
+   of class KLASS.  */
 
 inline bool
 fndecl_built_in_p (const_tree node, built_in_class klass)
@@ -5860,8 +5855,8 @@ fndecl_built_in_p (const_tree node, built_in_class klass)
   return (fndecl_built_in_p (node) && DECL_BUILT_IN_CLASS (node) == klass);
 }
 
-/* For a FUNCTION_DECL NODE, return true when a function is
-   a built-in of class KLASS with name equal to NAME.  */
+/* Return true if a FUNCTION_DECL NODE is a GCC built-in function
+   of class KLASS with name equal to NAME.  */
 
 inline bool
 fndecl_built_in_p (const_tree node, int name, built_in_class klass)
@@ -5869,8 +5864,8 @@ fndecl_built_in_p (const_tree node, int name, built_in_class klass)
   return (fndecl_built_in_p (node, klass) && DECL_FUNCTION_CODE (node) == name);
 }
 
-/* For a FUNCTION_DECL NODE, return true when a function is
-   a built-in of class BUILT_IN_NORMAL class with name equal to NAME.  */
+/* Return true if a FUNCTION_DECL NODE is a GCC built-in function
+   of BUILT_IN_NORMAL class with name equal to NAME.  */
 
 inline bool
 fndecl_built_in_p (const_tree node, built_in_function name)