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From: "tobi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/24568] [meta-bug] Missed optimization:
 trivialization of silly code
Date: Tue, 27 Jul 2021 02:41:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D24568

Tobias Schl=C3=BCter <tobi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #11 from Tobias Schl=C3=BCter <tobi at gcc dot gnu.org> ---
Take milliDiff =3D INT_MIN (<0).

 milliDiff_6 =3D -milliDiff_5(D);       // milliDiff_6 =3D INT_MIN (still <=
0)
 minutesDiff_13 =3D milliDiff_6 / 60000;// minutesDiff_13 =3D INT_MIN/60000=
 =3D
-35791;
 minutesDiff_8 =3D -minutesDiff_13;     // minutesDiff_8 =3D 35791 (>0!)

So negation and division don't commute over the two's complement integers, =
and
I don't think there is any bug left.  I'm taking the liberty to close this.=
=20
Link to a demonstration on the Compiler Explorer:
https://godbolt.org/z/hnjcMdjnq

Why the person who wrote that original bit of code wanted to deal with INT_=
MIN
(LONG_MIN in the original, but the testcase would overflow if sizeof(int) <
sizeof(long)) in this way is another question.=