diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index eb4c5c91090..2363216b73b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2018-02-22  Steve Ellcey  <sellcey@cavium.com>
+
+	* doc/extend.texi (__builtin_extend_pointer): Document builtin.
+
 2018-02-22  DJ Delorie  <dj@redhat.com>
 	    Sebastian Perta  <sebastian.perta@renesas.com>
 	    Oleg Endo  <olegendo@gcc.gnu.org>
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index b5240095ab6..1379502ebbb 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -11042,6 +11042,7 @@ the built-in function returns -1.
 @findex __builtin_alloca_with_align
 @findex __builtin_alloca_with_align_and_max
 @findex __builtin_call_with_static_chain
+@findex __builtin_extend_pointer
 @findex __builtin_fpclassify
 @findex __builtin_isfinite
 @findex __builtin_isnormal
@@ -12419,6 +12420,15 @@ Similar to @code{__builtin_bswap32}, except the argument and return types
 are 64 bit.
 @end deftypefn
 
+@deftypefn {Built-in Function} Pmode __builtin_extend_pointer (void * x)
+On targets where the user visible pointer size is smaller than the size
+of an actual hardware address this function returns the extended user
+pointer.  Targets where this is true included ILP32 mode on x86_64 or
+Aarch64.  This function is mainly useful when writing inline assembly
+code.
+@var{addr}
+@end deftypefn
+
 @node Target Builtins
 @section Built-in Functions Specific to Particular Target Machines