fold-const.c (fold_binary_loc): Preserve side-effects of X - X when simplifying to 0.

2014-10-22  Richard Biener  <rguenther@suse.de>

	* fold-const.c (fold_binary_loc): Preserve side-effects of
	X - X when simplifying to 0.
	* stor-layout.c (finish_bitfield_representative): Strip
	side-effects of evaluating the difference of two DECL_FIELD_OFFSET.

From-SVN: r216575

gcc/ChangeLog

+2014-10-23  Richard Biener  <rguenther@suse.de>
+
+	* fold-const.c (fold_binary_loc): Preserve side-effects of
+	X - X when simplifying to 0.
+	* stor-layout.c (finish_bitfield_representative): Strip
+	side-effects of evaluating the difference of two DECL_FIELD_OFFSET.
+
 2014-10-22  Richard Biener  <rguenther@suse.de>
 	    Tobias Burnus <burnus@net-b.de>
 

gcc/fold-const.c

@@ -10749,7 +10749,7 @@ fold_binary_loc (location_t loc,
 
       if ((!FLOAT_TYPE_P (type) || !HONOR_NANS (TYPE_MODE (type)))
 	  && operand_equal_p (arg0, arg1, 0))
-	return build_zero_cst (type);
+	return omit_one_operand_loc (loc, type, build_zero_cst (type), arg0);
 
       /* A - B -> A + (-B) if B is easily negatable.  */
       if (negate_expr_p (arg1)

gcc/stor-layout.c

@@ -1860,6 +1860,8 @@ finish_bitfield_representative (tree repr, tree field)
 
   size = size_diffop (DECL_FIELD_OFFSET (field),
 		      DECL_FIELD_OFFSET (repr));
+  while (TREE_CODE (size) == COMPOUND_EXPR)
+    size = TREE_OPERAND (size, 1);
   gcc_assert (tree_fits_uhwi_p (size));
   bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT
 	     + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))