einfo.ads (Size_Depends_On_Discriminant): Adjust description.

	* einfo.ads (Size_Depends_On_Discriminant): Adjust description.
	* layout.adb (Compute_Size_Depends_On_Discriminant): New procedure
	to compute Set_Size_Depends_On_Discriminant.
	(Layout_Type): Call it on array types in back-end layout mode.
	* sem_util.adb (Requires_Transient_Scope): Return true for array
	types only if the size depends on the value of discriminants.
	* gcc-interface/utils2.c (build_binary_op) <MODIFY_EXPR>: Use the RHS
	type if the RHS is a call to a function that returns an unconstrained
	type with default discriminant.

From-SVN: r171402

5 files changed, 88 insertions, 9 deletions

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index e586919..a76fb31 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,5 +1,17 @@
 2011-03-24  Eric Botcazou  <ebotcazou@adacore.com>
 
+	* einfo.ads (Size_Depends_On_Discriminant): Adjust description.
+	* layout.adb (Compute_Size_Depends_On_Discriminant): New procedure
+	to compute Set_Size_Depends_On_Discriminant.
+	(Layout_Type): Call it on array types in back-end layout mode.
+	* sem_util.adb (Requires_Transient_Scope): Return true for array
+	types only if the size depends on the value of discriminants.
+	* gcc-interface/utils2.c (build_binary_op) <MODIFY_EXPR>: Use the RHS
+	type if the RHS is a call to a function that returns an unconstrained
+	type with default discriminant.
+
+2011-03-24  Eric Botcazou  <ebotcazou@adacore.com>
+
 	* gcc-interface/trans.c (gnat_to_gnu): Remove obsolete case of
 	non-conversion to the nominal result type at the end.
 
diff --git a/gcc/ada/einfo.ads b/gcc/ada/einfo.ads
index 88fabd7..051688a 100644
--- a/gcc/ada/einfo.ads
+++ b/gcc/ada/einfo.ads
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 S p e c                                  --
 --                                                                          --
---          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2011, 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- --
@@ -3573,8 +3573,8 @@ package Einfo is
 --    Size_Depends_On_Discriminant (Flag177)
 --       Present in all entities for types and subtypes. Indicates that the
 --       size of the type depends on the value of one or more discriminants.
---       Currently, this flag is only set in front end layout mode for arrays
---       which have one or more bounds depending on a discriminant value.
+--       Currently, this flag is only set for arrays which have one or more
+--       bounds depending on a discriminant value.
 
 --    Size_Known_At_Compile_Time (Flag92)
 --       Present in all entities for types and subtypes. Indicates that the
diff --git a/gcc/ada/gcc-interface/utils2.c b/gcc/ada/gcc-interface/utils2.c
index 07d6b5b..78f5fd9 100644
--- a/gcc/ada/gcc-interface/utils2.c
+++ b/gcc/ada/gcc-interface/utils2.c
@@ -186,7 +186,7 @@ known_alignment (tree exp)
 static tree
 find_common_type (tree t1, tree t2)
 {
-  /* ??? As of today, various constructs lead here with types of different
+  /* ??? As of today, various constructs lead to here with types of different
      sizes even when both constants (e.g. tagged types, packable vs regular
      component types, padded vs unpadded types, ...).  While some of these
      would better be handled upstream (types should be made consistent before
@@ -609,6 +609,15 @@ build_binary_op (enum tree_code op_code, tree result_type,
 	       && !integer_zerop (TYPE_SIZE (right_type)))
 	operation_type = left_type;
 
+      /* If we have a call to a function that returns an unconstrained type
+	 with default discriminant on the RHS, use the RHS type (which is
+	 padded) as we cannot compute the size of the actual assignment.  */
+      else if (TREE_CODE (right_operand) == CALL_EXPR
+	       && TYPE_IS_PADDING_P (right_type)
+	       && CONTAINS_PLACEHOLDER_P
+		  (TYPE_SIZE (TREE_TYPE (TYPE_FIELDS (right_type)))))
+	operation_type = right_type;
+
       /* Find the best type to use for copying between aggregate types.  */
       else if (((TREE_CODE (left_type) == ARRAY_TYPE
 		 && TREE_CODE (right_type) == ARRAY_TYPE)
diff --git a/gcc/ada/layout.adb b/gcc/ada/layout.adb
index 0c4db36..7ae89b5 100644
--- a/gcc/ada/layout.adb
+++ b/gcc/ada/layout.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 2001-2010, Free Software Foundation, Inc.         --
+--          Copyright (C) 2001-2011, 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- --
@@ -109,6 +109,12 @@ package body Layout is
    --  are of an enumeration type (so that the subtraction cannot be
    --  done directly) by applying the Pos operator to Hi/Lo first.
 
+   procedure Compute_Size_Depends_On_Discriminant (E : Entity_Id);
+   --  Given an array type or an array subtype E, compute whether its size
+   --  depends on the value of one or more discriminants and set the flag
+   --  Size_Depends_On_Discriminant accordingly. This need not be called
+   --  in front end layout mode since it does the computation on its own.
+
    function Expr_From_SO_Ref
      (Loc  : Source_Ptr;
       D    : SO_Ref;
@@ -1289,6 +1295,49 @@ package body Layout is
       end if;
    end Layout_Array_Type;
 
+   ------------------------------------------
+   -- Compute_Size_Depends_On_Discriminant --
+   ------------------------------------------
+
+   procedure Compute_Size_Depends_On_Discriminant (E : Entity_Id) is
+      Indx : Node_Id;
+      Ityp : Entity_Id;
+      Lo   : Node_Id;
+      Hi   : Node_Id;
+      Res  : Boolean := False;
+   begin
+      --  Loop to process array indexes
+
+      Indx := First_Index (E);
+      while Present (Indx) loop
+         Ityp := Etype (Indx);
+
+         --  If an index of the array is a generic formal type then there is
+         --  no point in determining a size for the array type.
+
+         if Is_Generic_Type (Ityp) then
+            return;
+         end if;
+
+         Lo := Type_Low_Bound (Ityp);
+         Hi := Type_High_Bound (Ityp);
+
+         if (Nkind (Lo) = N_Identifier
+               and then Ekind (Entity (Lo)) = E_Discriminant)
+           or else (Nkind (Hi) = N_Identifier
+                      and then Ekind (Entity (Hi)) = E_Discriminant)
+         then
+            Res := True;
+         end if;
+
+         Next_Index (Indx);
+      end loop;
+
+      if Res then
+         Set_Size_Depends_On_Discriminant (E);
+      end if;
+   end Compute_Size_Depends_On_Discriminant;
+
    -------------------
    -- Layout_Object --
    -------------------
@@ -2631,6 +2680,15 @@ package body Layout is
                   Set_Alignment (E, Uint_1);
                end if;
             end if;
+
+            --  We need to know whether the size depends on the value of one
+            --  or more discriminants to select the return mechanism. Skip if
+            --  errors are present, to prevent cascaded messages.
+
+            if Serious_Errors_Detected = 0 then
+               Compute_Size_Depends_On_Discriminant (E);
+            end if;
+
          end if;
       end if;
 
diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
index b218b8ea..3a6ca5f 100644
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2011, 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- --
@@ -10473,11 +10473,11 @@ package body Sem_Util is
          if Requires_Transient_Scope (Component_Type (Typ)) then
             return True;
 
-         --  Otherwise, we only need a transient scope if the size is not
-         --  known at compile time.
+         --  Otherwise, we only need a transient scope if the size depends on
+         --  the value of one or more discriminants.
 
          else
-            return not Size_Known_At_Compile_Time (Typ);
+            return Size_Depends_On_Discriminant (Typ);
          end if;
 
       --  All other cases do not require a transient scope