commit c6669b5cde3d7b504aec388282e7af955af58681
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Mon Jul 20 15:02:17 2015 +0100

    [match.pd] PR middle-end/66915 Restrict A - B -> A + (-B) to non-fixed-point types

diff --git a/gcc/match.pd b/gcc/match.pd
index 4427000..3d7b32e 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -522,8 +522,8 @@ along with GCC; see the file COPYING3.  If not see
 /* A - B -> A + (-B) if B is easily negatable.  */
 (simplify
  (minus @0 negate_expr_p@1)
- (plus @0 (negate @1)))
-
+ (if (!FIXED_POINT_TYPE_P (type))
+ (plus @0 (negate @1))))
 
 /* Try to fold (type) X op CST -> (type) (X op ((type-x) CST))
    when profitable.