generic.texi (Adding new DECL node types): Explain *_CHECK macros.

gcc/
	* doc/generic.texi (Adding new DECL node types): Explain *_CHECK
	macros.

From-SVN: r203413

gcc/ChangeLog

 2013-10-11  Thomas Schwinge  <thomas@codesourcery.com>
 
+	* doc/generic.texi (Adding new DECL node types): Explain *_CHECK
+	macros.
+
 	* doc/gimple.texi (is_gimple_omp): Move into the correct section.
 
 	* acinclude.m4 (gcc_GAS_FLAGS): Add more gcc_cv_as_flags

gcc/doc/generic.texi

@@ -924,6 +924,11 @@ structures, something like the following should be used
    (BASE_STRUCT_CHECK(NODE)->base_struct.fieldname
 @end smallexample
 
+Reading them from the generated @file{all-tree.def} file (which in
+turn includes all the @file{tree.def} files), @file{gencheck.c} is
+used during GCC's build to generate the @code{*_CHECK} macros for all
+tree codes.
+
 @end table