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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111583] [13/14 Regression] Wrong code at -Os
 on x86_64-linux-gnu since r13-3281-g6cc3394507
Date: Mon, 25 Sep 2023 07:46:05 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111583

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-09-25

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

The problem is a latent bug in ldist.
It turns:
```
  <bb 5> [local count: 955630224]:
  a_5 =3D a_4 + 1;
  a.4_6 =3D (char *) a_4;
  *a.4_6 =3D 0;

  <bb 6> [local count: 1073741824]:
  # a_4 =3D PHI <a_2(4), a_5(5)>
  # j_7 =3D PHI <j_3(4), j_8(5)>
  j_8 =3D j_7 + 18446744073709551615;
  if (j_7 !=3D 0)
    goto <bb 5>; [89.00%]
  else
    goto <bb 7>; [11.00%]
```

Into:
```
  a_2 =3D (long int) k_1(D);
  j_3 =3D (long unsigned int) k_1(D);
  _23 =3D (sizetype) k_1(D);
  _25 =3D (char *) a_2;
  __builtin_memset (_25, 0, _23);
```

Which then basically says k!=3D0 as _25 can't be a null pointer.=