Index: exp_ch4.adb
===================================================================
--- exp_ch4.adb	(revision 192070)
+++ exp_ch4.adb	(working copy)
@@ -2325,9 +2325,12 @@
       Minimize_Eliminate_Overflow_Checks
         (Right_Opnd (N), Rlo, Rhi, Top_Level => False);
 
-      --  See if the range information decides the result of the comparison
+      --  See if the range information decides the result of the comparison.
+      --  We can only do this if we in fact have full range information (which
+      --  won't be the case if either operand is bignum at this stage).
 
-      case N_Op_Compare (Nkind (N)) is
+      if Llo /= No_Uint and then Rlo /= No_Uint then
+         case N_Op_Compare (Nkind (N)) is
          when N_Op_Eq =>
             if Llo = Lhi and then Rlo = Rhi and then Llo = Rlo then
                Set_True;
@@ -2369,12 +2372,13 @@
             elsif Llo > Rhi or else Lhi < Rlo then
                Set_True;
             end if;
-      end case;
+         end case;
 
-      --  All done if we did the rewrite
+         --  All done if we did the rewrite
 
-      if Nkind (N) not in N_Op_Compare then
-         return;
+         if Nkind (N) not in N_Op_Compare then
+            return;
+         end if;
       end if;
 
       --  Otherwise, time to do the comparison
Index: sem_eval.adb
===================================================================
--- sem_eval.adb	(revision 192070)
+++ sem_eval.adb	(working copy)
@@ -37,6 +37,7 @@
 with Nmake;    use Nmake;
 with Nlists;   use Nlists;
 with Opt;      use Opt;
+with Rtsfind;  use Rtsfind;
 with Sem;      use Sem;
 with Sem_Aux;  use Sem_Aux;
 with Sem_Cat;  use Sem_Cat;
@@ -5419,10 +5420,12 @@
             return;
          end if;
 
-         --  Type must be scalar or string type
+         --  Type must be scalar or string type (but allow Bignum, since this
+         --  is really a scalar type from our point of view in this diagnosis).
 
          if not Is_Scalar_Type (Typ)
            and then not Is_String_Type (Typ)
+           and then not Is_RTE (Typ, RE_Bignum)
          then
             Error_Msg_N
               ("static expression must have scalar or string type " &
@@ -5539,8 +5542,15 @@
 
          when N_Function_Call =>
             Why_Not_Static_List (Parameter_Associations (N));
-            Error_Msg_N ("non-static function call (RM 4.9(6,18))!", N);
 
+            --  Complain about non-static function call unless we have Bignum
+            --  which means that the underlying expression is really some
+            --  scalar arithmetic operation.
+
+            if not Is_RTE (Typ, RE_Bignum) then
+               Error_Msg_N ("non-static function call (RM 4.9(6,18))!", N);
+            end if;
+
          when N_Parameter_Association =>
             Why_Not_Static (Explicit_Actual_Parameter (N));