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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/109585] [10/11/12/13/14 regression] Carla/sord
 miscompiled with -O2 on ARM64 with flexible array member
Date: Mon, 24 Apr 2023 08:46:49 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 12.1.0
X-Bugzilla-Keywords: alias, wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109585

--- Comment #19 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Manually minimized testcase for investigation, miscompiled at -O2:

struct P {
        long v;
        struct P *n;
};

struct F {
        long x;
        struct P fam[];
};

int f(struct F *f, int i)
{
        struct P *p =3D f->fam;
        asm("" : "+r"(f): "r"(p));
        p->v =3D 0;
        p->n =3D 0;
        return f->fam->n !=3D 0;
}

Trunk emits:
f:
        lea     rdx, [rdi+8]
        mov     rax, rdi
        mov     QWORD PTR [rdi+8], 0
        cmp     QWORD PTR [rax+16], 0
        mov     QWORD PTR [rdi+16], 0
        setne   al
        movzx   eax, al
        ret=