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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/111151] [12/13/14 Regression] Wrong code at -O0 on
 x86_64-pc-linux-gnu
Date: Mon, 25 Mar 2024 11:01:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111151

--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #12)
> The following testcase at least reproduces the unsigned multiplication
> issue, but doesn't reproduce the signed multiplication nor division by -1.
> int
> main ()
> {
>   unsigned a =3D (1U + __INT_MAX__) / 2U;
>   unsigned b =3D 1U;
>   unsigned c =3D (a * 2U > b * 2U ? a * 2U : b * 2U) * 2U;
>   if (c !=3D 0U)
>     __builtin_abort ();
>   int d =3D (-__INT_MAX__ - 1) / 2;
>   int e =3D 10;
>   int f =3D (d * 2 > e * 2 ? d * 2 : e * 2) * 6;
>   if (f !=3D 120)
>     __builtin_abort ();
>   int g =3D (-__INT_MAX__ - 1) / 2;
>   int h =3D 0;
>   int i =3D (g * 2 > h * 2 ? g * 2 : h * 2) / -1;
>   if (i !=3D 0)
>     __builtin_abort ();
> }

Ah, the reason it doesn't fail for the f and i cases is that for the signed
type cases, we actually don't create a MIN_EXPR or MAX_EXPR but COND_EXPR w=
hich
just compares the vars and performs multiplication only in the COND_EXPR
second/third arguments.
So it is kind of hard trying to make it trigger for the problematic cases w=
here
the recursive calls would extract something.

Will see in full bootstrap/regtest with logging how often does the patch
trigger.=