varasm.c (initializer_constant_valid_p): Forbid view-conversions from aggregate…

varasm.c (initializer_constant_valid_p): Forbid view-conversions from aggregate to non-aggregate type if...

	* varasm.c (initializer_constant_valid_p): Forbid view-conversions
	from aggregate to non-aggregate type if the bit pattern is not fully
	preserved afterwards.

From-SVN: r140432

gcc/ChangeLog

+2008-09-17  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* varasm.c (initializer_constant_valid_p): Forbid view-conversions
+	from aggregate to non-aggregate type if the bit pattern is not fully
+	preserved afterwards.
+
 2008-09-17  Richard Guenther  <rguenther@suse.de>
 
 	* tree-cfg.c (verify_types_in_gimple_assign): Rename to ...

gcc/testsuite/ChangeLog

+2008-09-17  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/specs/static_initializer3.ads: New test.
+
 2008-09-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/37552

gcc/testsuite/gnat.dg/specs/static_initializer3.ads

+with Unchecked_Conversion;
+
+package Static_Initializer3 is
+
+  type Byte is range 0 .. 16#FF#;
+  for Byte'Size use 8;
+
+  type Word is range 0 .. 16#FFFF# ;
+  for Word'Size use 16;
+
+  type R is record
+    b1 : Boolean;
+    b2 : Boolean;
+  end record;
+  for R use record
+    b1 at 0 range 0..3;
+    b2 at 0 range 4..7;
+  end record;
+  for R'Size use 8;
+
+  function Conv is new Unchecked_Conversion (R, Byte);
+
+  C1 : constant Byte := Conv ((true, false));
+
+  C2 : constant Word := Word(C1);
+
+end Static_Initializer3;

gcc/varasm.c

@@ -4205,19 +4205,36 @@ initializer_constant_valid_p (tree value, tree endtype)
 	return op0;
       }
 
-    case VIEW_CONVERT_EXPR:
     case NON_LVALUE_EXPR:
       return initializer_constant_valid_p (TREE_OPERAND (value, 0), endtype);
 
-    CASE_CONVERT:
+    case VIEW_CONVERT_EXPR:
       {
-	tree src;
-	tree src_type;
-	tree dest_type;
+	tree src = TREE_OPERAND (value, 0);
+	tree src_type = TREE_TYPE (src);
+	tree dest_type = TREE_TYPE (value);
+
+	/* Allow view-conversions from aggregate to non-aggregate type only
+	   if the bit pattern is fully preserved afterwards; otherwise, the
+	   RTL expander won't be able to apply a subsequent transformation
+	   to the underlying constructor.  */
+	if (AGGREGATE_TYPE_P (src_type) && !AGGREGATE_TYPE_P (dest_type))
+	  {
+	    if (TYPE_MODE (endtype) == TYPE_MODE (dest_type))
+	      return initializer_constant_valid_p (src, endtype);
+	    else
+	      return NULL_TREE;
+	  }
+
+	/* Allow all other kinds of view-conversion.  */
+	return initializer_constant_valid_p (src, endtype);
+      }
 
-	src = TREE_OPERAND (value, 0);
-	src_type = TREE_TYPE (src);
-	dest_type = TREE_TYPE (value);
+    CASE_CONVERT:
+      {
+	tree src = TREE_OPERAND (value, 0);
+	tree src_type = TREE_TYPE (src);
+	tree dest_type = TREE_TYPE (value);
 
 	/* Allow conversions between pointer types, floating-point
 	   types, and offset types.  */