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From: "lin1.hu at intel dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/114700] Front-end optimization generates wrong code
 with -ftrapv.
Date: Fri, 12 Apr 2024 03:53:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114700

--- Comment #7 from lin1.hu at intel dot com ---
(In reply to Andrew Pinski from comment #5)
> From match.pd:
>   /* Match patterns that allow contracting a plus-minus pair
>      irrespective of overflow issues.  */
>   /* (A +- B) - A       ->  +- B */
>   /* (A +- B) -+ B      ->  A */
>   /* A - (A +- B)       -> -+ B */
>   /* A +- (B -+ A)      ->  +- B */
>   (simplify
>    (minus (nop_convert1? (plus:c (nop_convert2? @0) @1)) @0)
>    (view_convert @1))
>   (simplify
>    (minus (nop_convert1? (minus (nop_convert2? @0) @1)) @0)
>    (if (!ANY_INTEGRAL_TYPE_P (type)
>         || TYPE_OVERFLOW_WRAPS (type))
>    (negate (view_convert @1))
>    (view_convert (negate @1))))
>=20
> Looks like missing a TYPE_OVERFLOW_SANITIZED check.

OK, this looks like the same reason why z =3D c - y + a - c is not optimize=
d.=