--- a/gcc/ada/lib.adb	Thu Oct 25 07:37:49 2018 +0900
+++ b/gcc/ada/lib.adb	Thu Feb 13 11:34:05 2020 +0900
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2018, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2019, 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- --
@@ -277,8 +277,24 @@
    end Set_OA_Setting;
 
    procedure Set_Unit_Name (U : Unit_Number_Type; N : Unit_Name_Type) is
+      Old_N : constant Unit_Name_Type := Units.Table (U).Unit_Name;
+
    begin
+      --  First unregister the old name, if any
+
+      if Old_N /= No_Unit_Name and then Unit_Names.Get (Old_N) = U then
+         Unit_Names.Set (Old_N, No_Unit);
+      end if;
+
+      --  Then set the new name
+
       Units.Table (U).Unit_Name := N;
+
+      --  Finally register the new name
+
+      if Unit_Names.Get (N) = No_Unit then
+         Unit_Names.Set (N, U);
+      end if;
    end Set_Unit_Name;
 
    ------------------------------
@@ -1068,6 +1084,16 @@
       return TSN;
    end Increment_Serial_Number;
 
+   ----------------------
+   --  Init_Unit_Name  --
+   ----------------------
+
+   procedure Init_Unit_Name (U : Unit_Number_Type; N : Unit_Name_Type) is
+   begin
+      Units.Table (U).Unit_Name := N;
+      Unit_Names.Set (N, U);
+   end Init_Unit_Name;
+
    ----------------
    -- Initialize --
    ----------------
@@ -1087,13 +1113,7 @@
 
    function Is_Loaded (Uname : Unit_Name_Type) return Boolean is
    begin
-      for Unum in Units.First .. Units.Last loop
-         if Uname = Unit_Name (Unum) then
-            return True;
-         end if;
-      end loop;
-
-      return False;
+      return Unit_Names.Get (Uname) /= No_Unit;
    end Is_Loaded;
 
    ---------------
@@ -1141,6 +1161,7 @@
    procedure Remove_Unit (U : Unit_Number_Type) is
    begin
       if U = Units.Last then
+         Unit_Names.Set (Unit_Name (U), No_Unit);
          Units.Decrement_Last;
       end if;
    end Remove_Unit;
@@ -1277,6 +1298,15 @@
       end loop;
    end Tree_Write;
 
+   --------------------
+   -- Unit_Name_Hash --
+   --------------------
+
+   function Unit_Name_Hash (Id : Unit_Name_Type) return Unit_Name_Header_Num is
+   begin
+      return Unit_Name_Header_Num (Id mod Unit_Name_Table_Size);
+   end Unit_Name_Hash;
+
    ------------
    -- Unlock --
    ------------