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

	PR middle-end/66915
	* match.pd (A - B -> A + (-B)): Don't allow folding
	when type if a fixed-point type.

From-SVN: r226028

gcc/ChangeLog

+2015-07-21  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR middle-end/66915
+	* match.pd (A - B -> A + (-B)): Don't allow folding
+	when type if a fixed-point type.
+
 2015-07-20  DJ Delorie  <dj@redhat.com>
 
 	* config/rl78/rl78-real.md (andqi3_real): Expand operands for clr1.

gcc/match.pd

@@ -510,8 +510,8 @@ 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.