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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107131] [11/12 Regression] wrong code with -Os
 -fno-ipa-vrp -fno-tree-bit-ccp
Date: Thu, 27 Apr 2023 12:02:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107131

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #8)
> I think the problem happens during combine.  Parts of the vector code
> related to:
>   V b =3D (V) { } >=3D o;
>   V c =3D b <=3D (V)(b >=3D (V) { 0, 0, 0, 0, 0, 0x90DF0BE3990AC871ULL });
> - in particular the scalar c[5] computation, i.e.
> unsigned long long b =3D 0 >=3D o ? -1ULL : 0ULL;
> unsigned long long c =3D b <=3D (b >=3D 0x90DF0BE3990AC871ULL ? -1ULL : 0=
ULL) ?
> -1ULL : 0ULL;
> evaluates to 0 rather than -1 that it should when o is 0.
>=20
> This boils down to:
> __attribute__((noipa)) unsigned long long
> foo (unsigned char o)
> {
>   unsigned long long t1 =3D -(long long) (o =3D=3D 0);
>   unsigned long long t2 =3D -(long long) (t1 > 10439075533421201520ULL);
>   unsigned long long t3 =3D -(long long) (t1 <=3D t2);
>   return t3;
> }
>=20
> int
> main ()
> {
>   if (foo (0) !=3D -1ULL)
>     __builtin_abort ();
>   return 0;
> }
> at -O2 or -Os, which was miscompiled starting with r12-303-g86403f4e6e5f7=
216
> and got fixed with r13-3530-g0e36a9c6915c713d30.
> No idea why this is marked as 11 regression though...
>=20
> So, do we need to backport PR107172 change to 12 branch?

Yes.  Testing that now.=