[Ada] Remove deferred freezing of subprograms in Freeze_Entity

[Eric Botcazou <ebotcazou at adacore dot com>]

This removes the specific mechanism present in Freeze_Entity to defer the
freezing of functions returning an incomplete type coming from a limited
context.  It was invented to cope with the old elaboration model for
subprograms in gigi, which didn't really implement AI05-151 and AI05-019.
The new elaboration model implements both AIs so the mechanism is obsolete.

No functional change.  Tested on x86_64-suse-linux, applied on the mainline.


2016-06-06  Eric Botcazou  <ebotcazou@adacore.com>

	* einfo.ads (Returns_Limited_View): Remove.
	(Set_Returns_Limited_View ): Likewise.
	* einfo.adb (Returns_Limited_View): Likewise.
	(Set_Returns_Limited_View ): Likewise.
	* freeze.adb (Late_Freeze_Subprogram): Remove.
	(Freeze_Entity): Do not defer the freezing of functions returning an
	incomplete type coming from a limited context.

-- 
Eric Botcazou

Index: einfo.ads
===================================================================
--- einfo.ads	(revision 237088)
+++ einfo.ads	(working copy)
@@ -3973,12 +3973,6 @@ package Einfo is
 --       by reference, either because its return type is a by-reference-type
 --       or because the function explicitly uses the secondary stack.
 
---    Returns_Limited_View (Flag134)
---       Defined in function entities. Set if the return type of the function
---       at the point of definition is a limited view. Used to handle the late
---       freezing of the function when it is called in the current semantic
---       unit while it is still unfrozen.
-
 --    Reverse_Bit_Order (Flag164) [base type only]
 --       Defined in all record type entities. Set if entity has a Bit_Order
 --       aspect (set by an aspect clause or attribute definition clause) that
@@ -5972,7 +5966,6 @@ package Einfo is
    --    Requires_Overriding                 (Flag213)  (non-generic case only)
    --    Return_Present                      (Flag54)
    --    Returns_By_Ref                      (Flag90)
-   --    Returns_Limited_View                (Flag134)  (non-generic case only)
    --    Rewritten_For_C                     (Flag287)  (generate C code only)
    --    Sec_Stack_Needed_For_Return         (Flag167)
    --    SPARK_Pragma_Inherited              (Flag265)
@@ -7174,7 +7167,6 @@ package Einfo is
    function Return_Applies_To                   (Id : E) return N;
    function Return_Present                      (Id : E) return B;
    function Returns_By_Ref                      (Id : E) return B;
-   function Returns_Limited_View                (Id : E) return B;
    function Reverse_Bit_Order                   (Id : E) return B;
    function Reverse_Storage_Order               (Id : E) return B;
    function Rewritten_For_C                     (Id : E) return B;
@@ -7848,7 +7840,6 @@ package Einfo is
    procedure Set_Return_Applies_To               (Id : E; V : N);
    procedure Set_Return_Present                  (Id : E; V : B := True);
    procedure Set_Returns_By_Ref                  (Id : E; V : B := True);
-   procedure Set_Returns_Limited_View            (Id : E; V : B := True);
    procedure Set_Reverse_Bit_Order               (Id : E; V : B := True);
    procedure Set_Reverse_Storage_Order           (Id : E; V : B := True);
    procedure Set_Rewritten_For_C                 (Id : E; V : B := True);
@@ -8678,7 +8669,6 @@ package Einfo is
    pragma Inline (Return_Applies_To);
    pragma Inline (Return_Present);
    pragma Inline (Returns_By_Ref);
-   pragma Inline (Returns_Limited_View);
    pragma Inline (Reverse_Bit_Order);
    pragma Inline (Reverse_Storage_Order);
    pragma Inline (Rewritten_For_C);
@@ -9143,7 +9133,6 @@ package Einfo is
    pragma Inline (Set_Return_Applies_To);
    pragma Inline (Set_Return_Present);
    pragma Inline (Set_Returns_By_Ref);
-   pragma Inline (Set_Returns_Limited_View);
    pragma Inline (Set_Reverse_Bit_Order);
    pragma Inline (Set_Reverse_Storage_Order);
    pragma Inline (Set_Rewritten_For_C);
Index: einfo.adb
===================================================================
--- einfo.adb	(revision 237088)
+++ einfo.adb	(working copy)
@@ -432,7 +432,6 @@ package body Einfo is
    --    No_Pool_Assigned                Flag131
    --    Is_Default_Init_Cond_Procedure  Flag132
    --    Has_Inherited_Default_Init_Cond Flag133
-   --    Returns_Limited_View            Flag134
    --    Has_Aliased_Components          Flag135
    --    No_Strict_Aliasing              Flag136
    --    Is_Machine_Code_Subprogram      Flag137
@@ -3065,12 +3064,6 @@ package body Einfo is
       return Flag90 (Id);
    end Returns_By_Ref;
 
-   function Returns_Limited_View (Id : E) return B is
-   begin
-      pragma Assert (Ekind (Id) = E_Function);
-      return Flag134 (Id);
-   end Returns_Limited_View;
-
    function Reverse_Bit_Order (Id : E) return B is
    begin
       pragma Assert (Is_Record_Type (Id));
@@ -6142,12 +6135,6 @@ package body Einfo is
       Set_Flag90 (Id, V);
    end Set_Returns_By_Ref;
 
-   procedure Set_Returns_Limited_View (Id : E; V : B := True) is
-   begin
-      pragma Assert (Ekind (Id) = E_Function);
-      Set_Flag134 (Id, V);
-   end Set_Returns_Limited_View;
-
    procedure Set_Reverse_Bit_Order (Id : E; V : B := True) is
    begin
       pragma Assert
@@ -9141,7 +9128,6 @@ package body Einfo is
       W ("Requires_Overriding",             Flag213 (Id));
       W ("Return_Present",                  Flag54  (Id));
       W ("Returns_By_Ref",                  Flag90  (Id));
-      W ("Returns_Limited_View",            Flag134 (Id));
       W ("Reverse_Bit_Order",               Flag164 (Id));
       W ("Reverse_Storage_Order",           Flag93  (Id));
       W ("Rewritten_For_C",                 Flag287 (Id));
Index: freeze.adb
===================================================================
--- freeze.adb	(revision 237088)
+++ freeze.adb	(working copy)
@@ -1934,9 +1934,6 @@ package body Freeze is
       Has_Default_Initialization : Boolean := False;
       --  This flag gets set to true for a variable with default initialization
 
-      Late_Freezing : Boolean := False;
-      --  Used to detect attempt to freeze function declared in another unit
-
       Result : List_Id := No_List;
       --  List of freezing actions, left at No_List if none
 
@@ -1973,9 +1970,8 @@ package body Freeze is
 
       function Freeze_Profile (E : Entity_Id) return Boolean;
       --  Freeze formals and return type of subprogram. If some type in the
-      --  profile is a limited view, freezing of the entity will take place
-      --  elsewhere, and the function returns False. This routine will be
-      --  modified if and when we can implement AI05-019 efficiently ???
+      --  profile is incomplete and we are in an instance, freezing of the
+      --  entity will take place elsewhere, and the function returns False.
 
       procedure Freeze_Record_Type (Rec : Entity_Id);
       --  Freeze record type, including freezing component types, and freezing
@@ -1985,16 +1981,6 @@ package body Freeze is
       --  Determine whether an arbitrary entity is subject to Boolean aspect
       --  Import and its value is specified as True.
 
-      procedure Late_Freeze_Subprogram (E : Entity_Id);
-      --  Following AI05-151, a function can return a limited view of a type
-      --  declared elsewhere. In that case the function cannot be frozen at
-      --  the end of its enclosing package. If its first use is in a different
-      --  unit, it cannot be frozen there, but if the call is legal the full
-      --  view of the return type is available and the subprogram can now be
-      --  frozen. However the freeze node cannot be inserted at the point of
-      --  call, but rather must go in the package holding the function, so that
-      --  the backend can process it in the proper context.
-
       function New_Freeze_Node return Node_Id;
       --  Create a new freeze node for entity E
 
@@ -3300,15 +3286,6 @@ package body Freeze is
 
          if Ekind (E) = E_Function then
 
-            --  Check whether function is declared elsewhere. Previous code
-            --  used Get_Source_Unit on both arguments, but the values are
-            --  equal in the case of a parent and a child unit.
-            --  Confusion with subunits in code  ????
-
-            Late_Freezing :=
-              not In_Same_Extended_Unit (E, N)
-                and then Returns_Limited_View (E);
-
             --  Freeze return type
 
             R_Type := Etype (E);
@@ -3326,24 +3303,6 @@ package body Freeze is
             then
                R_Type := Full_View (R_Type);
                Set_Etype (E, R_Type);
-
-            --  If the return type is a limited view and the non-limited
-            --  view is still incomplete, the function has to be frozen at a
-            --  later time. If the function is abstract there is no place at
-            --  which the full view will become available, and no code to be
-            --  generated for it, so mark type as frozen.
-
-            elsif Ekind (R_Type) = E_Incomplete_Type
-              and then From_Limited_With (R_Type)
-              and then Ekind (Non_Limited_View (R_Type)) = E_Incomplete_Type
-            then
-               if Is_Abstract_Subprogram (E) then
-                  null;
-               else
-                  Set_Is_Frozen (E, False);
-                  Set_Returns_Limited_View (E);
-                  return False;
-               end if;
             end if;
 
             Freeze_And_Append (R_Type, N, Result);
@@ -4613,25 +4572,6 @@ package body Freeze is
          return False;
       end Has_Boolean_Aspect_Import;
 
-      ----------------------------
-      -- Late_Freeze_Subprogram --
-      ----------------------------
-
-      procedure Late_Freeze_Subprogram (E : Entity_Id) is
-         Spec  : constant Node_Id :=
-                   Specification (Unit_Declaration_Node (Scope (E)));
-         Decls : List_Id;
-
-      begin
-         if Present (Private_Declarations (Spec)) then
-            Decls := Private_Declarations (Spec);
-         else
-            Decls := Visible_Declarations (Spec);
-         end if;
-
-         Append_List (Result, Decls);
-      end Late_Freeze_Subprogram;
-
       ---------------------
       -- New_Freeze_Node --
       ---------------------
@@ -5111,12 +5051,6 @@ package body Freeze is
                Freeze_Subprogram (E);
             end if;
 
-            if Late_Freezing then
-               Late_Freeze_Subprogram (E);
-               Ghost_Mode := Save_Ghost_Mode;
-               return No_List;
-            end if;
-
             --  If warning on suspicious contracts then check for the case of
             --  a postcondition other than False for a No_Return subprogram.