re PR middle-end/62103 (Incorrect folding of bitfield in a union on big endian targets)

2014-08-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR middle-end/62103
    * gimple-fold.c (fold_ctor_reference): Don't fold in presence of
    bitfields, that is when size doesn't match the size of type or the
    size of the constructor.

    gcc/testsuite/
    PR middle-end/62103
    * gcc.c-torture/execute/bitfld-6.c: New test.

From-SVN: r213846

gcc/ChangeLog

+2014-08-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	PR middle-end/62103
+	* gimple-fold.c (fold_ctor_reference): Don't fold in presence of
+	bitfields, that is when size doesn't match the size of type or the
+	size of the constructor.
+
 2014-08-11  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	* config/rs6000/constraints.md (wh constraint): New constraint,

gcc/gimple-fold.c

@@ -4355,8 +4355,8 @@ fold_ctor_reference (tree type, tree ctor, unsigned HOST_WIDE_INT offset,
      result.  */
   if (!AGGREGATE_TYPE_P (TREE_TYPE (ctor)) && !offset
       /* VIEW_CONVERT_EXPR is defined only for matching sizes.  */
-      && operand_equal_p (TYPE_SIZE (type),
-			  TYPE_SIZE (TREE_TYPE (ctor)), 0))
+      && !compare_tree_int (TYPE_SIZE (type), size)
+      && !compare_tree_int (TYPE_SIZE (TREE_TYPE (ctor)), size))
     {
       ret = canonicalize_constructor_val (unshare_expr (ctor), from_decl);
       ret = fold_unary (VIEW_CONVERT_EXPR, type, ret);

gcc/testsuite/ChangeLog

+2014-08-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	PR middle-end/62103
+	* gcc.c-torture/execute/bitfld-6.c: New test.
+
 2014-08-11  Janis Johnson  <janisjo@codesourcery.com>
 
 	* gcc.target/arm/frame-pointer-1.c: Skip if Thumb is not supported.

gcc/testsuite/gcc.c-torture/execute/bitfld-6.c

+union U
+{
+  const int a;
+  unsigned b : 20;
+};
+
+static union U u = { 0x12345678 };
+
+/* Constant folding used to fail to account for endianness when folding a
+   union.  */
+
+int
+main (void)
+{
+#ifdef __BYTE_ORDER__
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  return u.b - 0x45678;
+#else
+  return u.b - 0x12345;
+#endif
+#endif
+  return 0;
+}