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

2015-02-04  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR middle-end/62103
    * tree-ssa-sccvn.c (fully_constant_vn_reference_p): Use TYPE_PRECISION
    to compute size of referenced value in the constant case.

    gcc/testsuite/
    PR middle-end/62103
    * gcc.c-torture/execute/bitfld-7.c: New test adapted from bitfld-6.c
    to use 24 bits for bitfield b.

From-SVN: r220390

gcc/ChangeLog

+2015-02-04  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	PR middle-end/62103
+	* tree-ssa-sccvn.c (fully_constant_vn_reference_p): Use TYPE_PRECISION
+	to compute size of referenced value in the constant case.
+
 2015-02-03  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/64756

gcc/testsuite/ChangeLog

 2015-02-04  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
+	PR middle-end/62103
+	* gcc.c-torture/execute/bitfld-7.c: New test adapted from bitfld-6.c
+	to use 24 bits for bitfield b.
+
+2015-02-04  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
 	PR testsuite/64796
 	* lib/target-supports.exp (check_effective_target_bswap64): Do not
 	cache result in a global variable.  Include all 32-bit targets for

gcc/testsuite/gcc.c-torture/execute/bitfld-7.c

+union U
+{
+  const int a;
+  unsigned b : 24;
+};
+
+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 - 0x345678;
+#else
+  return u.b - 0x123456;
+#endif
+#endif
+  return 0;
+}

gcc/tree-ssa-sccvn.c

@@ -1352,7 +1352,7 @@ fully_constant_vn_reference_p (vn_reference_t ref)
 	       || TYPE_PRECISION (ref->type) % BITS_PER_UNIT == 0))
     {
       HOST_WIDE_INT off = 0;
-      HOST_WIDE_INT size = tree_to_shwi (TYPE_SIZE (ref->type));
+      HOST_WIDE_INT size = TYPE_PRECISION (ref->type);
       if (size % BITS_PER_UNIT != 0
 	  || size > MAX_BITSIZE_MODE_ANY_MODE)
 	return NULL_TREE;