--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/ada/libgnat/s-expuns.adb	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,73 @@
+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT RUN-TIME COMPONENTS                         --
+--                                                                          --
+--                       S Y S T E M . E X P _ U N S                        --
+--                                                                          --
+--                                 B o d y                                  --
+--                                                                          --
+--          Copyright (C) 1992-2017, Free Software Foundation, Inc.         --
+--                                                                          --
+-- GNAT is free software;  you can  redistribute it  and/or modify it under --
+-- terms of the  GNU General Public License as published  by the Free Soft- --
+-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
+-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
+--                                                                          --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception,   --
+-- version 3.1, as published by the Free Software Foundation.               --
+--                                                                          --
+-- You should have received a copy of the GNU General Public License and    --
+-- a copy of the GCC Runtime Library Exception along with this program;     --
+-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
+-- <http://www.gnu.org/licenses/>.                                          --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc.      --
+--                                                                          --
+------------------------------------------------------------------------------
+
+with System.Unsigned_Types; use System.Unsigned_Types;
+
+package body System.Exp_Uns is
+
+   ------------------
+   -- Exp_Unsigned --
+   ------------------
+
+   function Exp_Unsigned
+     (Left  : Unsigned;
+      Right : Natural)
+      return  Unsigned
+   is
+      Result  : Unsigned := 1;
+      Factor  : Unsigned := Left;
+      Exp     : Natural := Right;
+
+   begin
+      --  We use the standard logarithmic approach, Exp gets shifted right
+      --  testing successive low order bits and Factor is the value of the
+      --  base raised to the next power of 2.
+
+      --  Note: it is not worth special casing the cases of base values -1,0,+1
+      --  since the expander does this when the base is a literal, and other
+      --  cases will be extremely rare.
+
+      if Exp /= 0 then
+         loop
+            if Exp rem 2 /= 0 then
+               Result := Result * Factor;
+            end if;
+
+            Exp := Exp / 2;
+            exit when Exp = 0;
+            Factor := Factor * Factor;
+         end loop;
+      end if;
+
+      return Result;
+   end Exp_Unsigned;
+
+end System.Exp_Uns;