[gcc(refs/vendors/ibm/heads/perf)] Clear --help=language and --help=common interaction.

[Jiu Fu Guo]

https://gcc.gnu.org/g:c7ec2f9ff6d064c4d446dbf521d554eb10254d34

commit c7ec2f9ff6d064c4d446dbf521d554eb10254d34
Author: Martin Liska <mliska@suse.cz>
Date:   Wed Mar 4 09:31:55 2020 +0100

    Clear --help=language and --help=common interaction.
    
            PR c/93886
            PR c/93887
            * doc/invoke.texi: Clarify --help=language and --help=common
            interaction.

Diff:
---
 gcc/ChangeLog       | 7 +++++++
 gcc/doc/invoke.texi | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index caa854d5a43..a08bdaf8ecd 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2020-03-04  Martin Liska  <mliska@suse.cz>
+
+	PR c/93886
+	PR c/93887
+	* doc/invoke.texi: Clarify --help=language and --help=common
+	interaction.
+
 2020-03-04  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/94001
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 54375ebd679..f51729d0e39 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1665,7 +1665,8 @@ option.
 @item @var{language}
 Display the options supported for @var{language}, where
 @var{language} is the name of one of the languages supported in this
-version of GCC@.
+version of GCC@.  If an option is supported by all languages, one needs
+to select @samp{common} class.
 
 @item @samp{common}
 Display the options that are common to all languages.