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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/55177] missed optimizations with
 __builtin_bswap
Date: Mon, 15 Nov 2021 08:35:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D55177

--- Comment #22 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #20)
> So the original testcase shows there are missing other bitop related
> optimizations on the tree level and conversions.
> I have two patches which fix the original issue.
> The first patch also fixes:
> unsigned foo(unsigned x, int b)
> {
>   int a =3D x;
>   a &=3D b;
>   x =3D a;
>   x |=3D b;
>   return x;
> }
> --- CUT ---
> The problem here is:
>   a_3 =3D (int) x_2(D);
>   a_5 =3D a_3 & b_4(D);
>   x_6 =3D (unsigned int) a_5;
>=20
> is not optimized to:
>   _7 =3D (unsigned int) b_4(D);
>   x_6 =3D _6 & x_2(D);
>=20
> Which shows up in testcase in comment #0:
>   _2 =3D __builtin_bswap32 (x.0_1);
>   a_6 =3D (int) _2;
>   a_7 =3D a_6 & 1515936861;
>   a.1_3 =3D (unsigned int) a_7;
>   _4 =3D __builtin_bswap32 (a.1_3);
>=20
> Fixing the bitop with convert, we get rid of the two byteswaps in comment=
 #0.

That I happened to file as PR 103228 a few days ago but only on accident wh=
ile
looking into a different issue.  Since PR 60669 is now fixed, I will test my
original patch to fix this.=