diff --git a/gas/ChangeLog b/gas/ChangeLog
index add6fd89eed..24320b3523e 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,7 @@
+2020-09-01  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* doc/as.texi: Document the .tls_common directive.
+
 2020-09-01  Alan Modra  <amodra@gmail.com>
 
 	PR 26420
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index 4f86e21a898..112eaf810cd 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -4507,6 +4507,9 @@ Some machine configurations provide additional directives.
 
 * Text::                        @code{.text @var{subsection}}
 * Title::                       @code{.title "@var{heading}"}
+@ifset ELF
+* Tls_common::                  @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
+@end ifset
 @ifset COFF-ELF
 * Type::                        @code{.type <@var{int} | @var{name} , @var{type description}>}
 @end ifset
@@ -7182,6 +7185,16 @@ source file name and pagenumber) when generating assembly listings.
 This directive affects subsequent pages, as well as the current page if
 it appears within ten lines of the top of a page.
 
+@ifset ELF
+@node Tls_common
+@section @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
+
+@cindex @code{tls_common} directive
+This directive behaves in the same way as the @code{.comm} directive
+(@pxref{Comm}) except that @var{symbol} has type of STT_TLS instead of
+STT_OBJECT.
+@end ifset
+
 @ifset COFF-ELF
 @node Type
 @section @code{.type}