trans.c (Attribute_to_gnu): Look through a view conversion from constrained to unconstrained form.

* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Length>: Look through
	a view conversion from constrained to unconstrained form.

From-SVN: r193751

gcc/ada/ChangeLog

@@ -1,3 +1,8 @@
+2012-11-23  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Length>: Look through
+	a view conversion from constrained to unconstrained form.
+
 2012-11-23  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc-interface/decl.c (components_need_strict_alignment): New.

gcc/ada/gcc-interface/trans.c

@@ -1700,7 +1700,20 @@ Attribute_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p, int attribute)
 	      gnat_param = Entity (Prefix (gnat_prefix));
 	  }
 
-	gnu_type = TREE_TYPE (gnu_prefix);
+	/* If the prefix is the view conversion of a constrained array to an
+	   unconstrained form, we retrieve the constrained array because we
+	   might not be able to substitute the PLACEHOLDER_EXPR coming from
+	   the conversion.  This can occur with the 'Old attribute applied
+	   to a parameter with an unconstrained type, which gets rewritten
+	   into a constrained local variable very late in the game.  */
+	if (TREE_CODE (gnu_prefix) == VIEW_CONVERT_EXPR
+	    && CONTAINS_PLACEHOLDER_P (TYPE_SIZE (TREE_TYPE (gnu_prefix)))
+	    && !CONTAINS_PLACEHOLDER_P
+	        (TYPE_SIZE (TREE_TYPE (TREE_OPERAND (gnu_prefix, 0)))))
+	  gnu_type = TREE_TYPE (TREE_OPERAND (gnu_prefix, 0));
+	else
+	  gnu_type = TREE_TYPE (gnu_prefix);
+
 	prefix_unused = true;
 	gnu_result_type = get_unpadded_type (Etype (gnat_node));
 

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2012-11-23  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/discr40.ad[sb]: New test.
+
 2012-11-23  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/discr39.adb: New test.

gcc/testsuite/gnat.dg/discr40.adb

@@ -0,0 +1,12 @@
+-- { dg-do compile }
+-- { dg-options "-gnat12 -gnata" }
+
+package body Discr40 is
+
+   procedure Push (S: in out Stack; E : Element) is
+   begin
+      S.Length := S.Length + 1;
+      S.Data(S.Length) := E;
+   end Push;
+
+end Discr40;

gcc/testsuite/gnat.dg/discr40.ads

@@ -0,0 +1,26 @@
+pragma Assertion_Policy(Check);
+
+package Discr40 is
+
+   subtype Element is Integer;
+
+   type Vector is array (Positive range <>) of Element;
+
+   type Stack (Max_Length : Natural) is
+   record
+      Length : Natural;
+      Data : Vector (1 .. Max_Length);
+   end record;
+
+   function Not_Full (S : Stack) return Boolean is
+      (S.Length < S.Max_Length);
+
+    procedure Push (S: in out Stack; E : Element)
+         with Pre => Not_Full(S),   -- Precodition
+              Post =>             -- Postcondition
+                 (S.Length = S'Old.Length + 1) and
+                 (S.Data (S.Length) = E) and
+                 (for all J in 1 .. S'Old.Length =>
+                     S.Data(J) = S'Old.Data(J));
+
+end Discr40;