[Ada] New pragma Aggregate_Individually_Assign

Where possible GNAT will store the binary representation of a record
aggregate in memory for space and performance reasons. This
configuration pragma changes this behaviour so that record aggregates
are instead always converted into individual assignment statements.

The following package pack.ads:

-- pack.ads

pragma Aggregate_Individually_Assign;
pragma Restrictions (No_Multiple_Elaboration);

package Pack is
   type A_Rec is record
      A, B, C, D : Boolean;
   end record;

   A : A_Rec := (True, False, True, True);
end Pack;

when compiled with

gcc -c -gnatdg pack.ads

should produce the following output:

Source recreated from tree for Pack (spec)
------------------------------------------

pragma aggregate_individually_assign;
pragma restrictions (no_multiple_elaboration);

package pack is
   type pack__a_rec is record
      a : boolean;
      b : boolean;
      c : boolean;
      d : boolean;
   end record;
   freeze pack__a_rec [
      procedure pack__a_recIP (_init : out pack__a_rec) is
      begin
         %push_constraint_error_label ()
         %push_program_error_label ()
         %push_storage_error_label ()
         null;
         %pop_constraint_error_label
         %pop_program_error_label
         %pop_storage_error_label
         return;
      end pack__a_recIP;
   ]
   pack__a : pack__a_rec := (
      a => true,
      b => false,
      c => true,
      d => true);
   pack__a.a := true;
   pack__a.b := false;
   pack__a.c := true;
   pack__a.d := true;
   null;
end pack;

2019-08-20  Patrick Bernardi  <bernardi@adacore.com>

gcc/ada/

	* exp_aggr.adb (Expand_Record_Aggregate): Always convert a
	record Aggregate to assignment statements if the option
	Aggregate_Individually_Assign is set.
	* opt.ads (Aggregate_Individually_Assign): New option.
	* par-prag.adb (Prag): Add Pragma_Aggregate_Individually_Assign.
	* sem_prag.adb (Analyze_Pragma): Likewise.
	* snames.ads-tmpl: Add Pragma_Aggregate_Individually_Assign and
	Name_Aggregate_Individually_Assign.
	* doc/gnat_rm/implementation_defined_pragmas.rst: Document
	pragma Aggregate_Individually_Assign.
	* gnat_rm.texi: Regenerate.

From-SVN: r274730

gcc/ada/ChangeLog

@@ -1,3 +1,17 @@
+2019-08-20  Patrick Bernardi  <bernardi@adacore.com>
+
+	* exp_aggr.adb (Expand_Record_Aggregate): Always convert a
+	record Aggregate to assignment statements if the option
+	Aggregate_Individually_Assign is set.
+	* opt.ads (Aggregate_Individually_Assign): New option.
+	* par-prag.adb (Prag): Add Pragma_Aggregate_Individually_Assign.
+	* sem_prag.adb (Analyze_Pragma): Likewise.
+	* snames.ads-tmpl: Add Pragma_Aggregate_Individually_Assign and
+	Name_Aggregate_Individually_Assign.
+	* doc/gnat_rm/implementation_defined_pragmas.rst: Document
+	pragma Aggregate_Individually_Assign.
+	* gnat_rm.texi: Regenerate.
+
 2019-08-20  Bob Duff  <duff@adacore.com>
 
 	* par-ch4.adb: Minor wording change in error messages.

gcc/ada/doc/gnat_rm/implementation_defined_pragmas.rst

@@ -371,6 +371,21 @@ Syntax:
 This configuration pragma is a synonym for pragma Ada_12 and has the
 same syntax and effect.
 
+Pragma Aggregate_Individually_Assign
+====================================
+
+Syntax:
+
+.. code-block:: ada
+
+  pragma Aggregate_Individually_Assign;
+
+Where possible GNAT will store the binary representation of a record aggregate
+in memory for space and performance reasons. This configuration pragma changes
+this behaviour so that record aggregates are instead always converted into
+individual assignment statements.
+
+
 Pragma Allow_Integer_Address
 ============================
 

gcc/ada/exp_aggr.adb

@@ -7478,6 +7478,12 @@ package body Exp_Aggr is
          return;
       end if;
 
+      --  If the pramga Aggregate_Individually_Assign is set always convert to
+      --  assignments.
+
+      if Aggregate_Individually_Assign then
+         Convert_To_Assignments (N, Typ);
+
       --  Ada 2005 (AI-318-2): We need to convert to assignments if components
       --  are build-in-place function calls. The assignments will each turn
       --  into a build-in-place function call. If components are all static,
@@ -7486,7 +7492,7 @@ package body Exp_Aggr is
       --  Extension aggregates, aggregates in extended return statements, and
       --  aggregates for C++ imported types must be expanded.
 
-      if Ada_Version >= Ada_2005 and then Is_Limited_View (Typ) then
+      elsif Ada_Version >= Ada_2005 and then Is_Limited_View (Typ) then
          if not Nkind_In (Parent (N), N_Component_Association,
                                       N_Object_Declaration)
          then

gcc/ada/opt.ads

@@ -191,6 +191,11 @@ package Opt is
    --  GNAT, GNATBIND
    --  Set True if package System has the line "type Address is private;"
 
+   Aggregate_Individually_Assign : Boolean := False;
+   --  GNAT
+   --  Set True if record aggregates are to be always converted into assignment
+   --  statements. Set through the corresponding pragma.
+
    All_Errors_Mode : Boolean := False;
    --  GNAT
    --  Flag set to force display of multiple errors on a single line and

gcc/ada/par-prag.adb

@@ -1319,6 +1319,7 @@ begin
          | Pragma_Acc_Kernels
          | Pragma_Acc_Loop
          | Pragma_Acc_Parallel
+         | Pragma_Aggregate_Individually_Assign
          | Pragma_Async_Readers
          | Pragma_Async_Writers
          | Pragma_Assertion_Policy

gcc/ada/sem_prag.adb

@@ -12979,6 +12979,18 @@ package body Sem_Prag is
             Ada_Version_Explicit := Ada_2020;
             Ada_Version_Pragma   := N;
 
+         -------------------------------------
+         -- Aggregate_Individually_Assign --
+         -------------------------------------
+
+         --  pragma Aggregate_Individually_Assign;
+
+         when Pragma_Aggregate_Individually_Assign =>
+            GNAT_Pragma;
+            Check_Arg_Count (0);
+            Check_Valid_Configuration_Pragma;
+            Aggregate_Individually_Assign := True;
+
          ----------------------
          -- All_Calls_Remote --
          ----------------------
@@ -30890,6 +30902,7 @@ package body Sem_Prag is
       Pragma_Ada_12                         => -1,
       Pragma_Ada_2012                       => -1,
       Pragma_Ada_2020                       => -1,
+      Pragma_Aggregate_Individually_Assign  => 0,
       Pragma_All_Calls_Remote               => -1,
       Pragma_Allow_Integer_Address          => -1,
       Pragma_Annotate                       => 93,

gcc/ada/snames.ads-tmpl

@@ -389,6 +389,7 @@ package Snames is
    Name_Ada_12                         : constant Name_Id := N + $; -- GNAT
    Name_Ada_2012                       : constant Name_Id := N + $; -- GNAT
    Name_Ada_2020                       : constant Name_Id := N + $; -- GNAT
+   Name_Aggregate_Individually_Assign  : constant Name_Id := N + $; -- GNAT
    Name_Allow_Integer_Address          : constant Name_Id := N + $; -- GNAT
    Name_Annotate                       : constant Name_Id := N + $; -- GNAT
    Name_Assertion_Policy               : constant Name_Id := N + $; -- Ada 05
@@ -1847,6 +1848,7 @@ package Snames is
       Pragma_Ada_2020,
       --  Note that there is no Pragma_Ada_20. Pragma_Ada_05/12 are for
       --  compatibility reasons only; the full year names are preferred.
+      Pragma_Aggregate_Individually_Assign,
       Pragma_Allow_Integer_Address,
       Pragma_Annotate,
       Pragma_Assertion_Policy,