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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/55190] ivopts causes loop setup bloat
Date: Fri, 07 Jul 2023 06:49:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D55190

--- Comment #12 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #0)
> The following code:
>=20
> struct X
> {
>   int a, b, c, d, e;
> };
>=20
> int test (X* x, unsigned int c)
> {
>   int s =3D 0;
>   unsigned int i;
>   for (i =3D 0; i < c; ++i)
>     s +=3D x[i].b;
>   return s;
> }
>=20
> results in:
>         tst     r5,r5
>         bt/s    .L4
>         mov     r5,r1
>         shll2   r1
>         add     r5,r1
>         mov.l   .L9,r2
>         shll2   r1
>         add     #-20,r1
>         shlr2   r1
>         mul.l   r2,r1
>         mov.l   .L10,r2
>         add     #4,r4
>         mov     #0,r0
>         sts     macl,r1
>         and     r2,r1
>         add     #1,r1
> .L3:
>         mov.l   @r4,r2
>         dt      r1
>         add     #20,r4
>         bf/s    .L3
>         add     r2,r0
>         rts
>         nop
> .L4:
>         rts
>         mov     #0,r0
> .L11:
>         .align 2
> .L9:
>         .long   214748365
> .L10:
>         .long   1073741823
>=20

As of GCC 13, this still produces the same code with loop header bloat.=