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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/110582] [14 Regression] Wrong code at -O2/3
 on x86_64-linux-gnu
Date: Sat, 08 Jul 2023 01:08:44 +0000
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X-Bugzilla-Component: tree-optimization
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X-Bugzilla-Keywords: needs-bisection, wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110582

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #2)
> It works with -fno-tree-loop-optimize but the difference from loop opts is
> just

So changing it to what -ftree-loop-optimize, it still passes with
-fno-tree-loop-optimize (which is even odder):
```
int a, b;
int main() {
  char c =3D a =3D 0;
  unsigned char t =3D 253;
  for (; t !=3D 0; t --){
    int d =3D 2;
    d ^=3D 2 && a;
    b =3D a =3D=3D 0 ? d : d / a;
    a =3D b;
  }
  for (; (1 + 95 << 24) + b + 1 + 686658714L + b - 2297271457;)
    ;
}
```

The difference in this case is:
+  unsigned charD.20 ivtmp_32;
+  unsigned charD.20 ivtmp_33;
...
-  # RANGE [irange] unsigned char [1, 253]
-  # t_19 =3D PHI <t_16(5), 253(2)>
   # .MEM_20 =3D PHI <.MEM_20(5), .MEM_11(D)(2)>
   # a_lsm.11_2 =3D PHI <iftmp.1_9(5), 0(2)>
+  # ivtmp_33 =3D PHI <ivtmp_32(5), 253(2)>

...
-  # RANGE [irange] unsigned char [0, 252]
-  t_16 =3D t_19 + 255;
-  if (t_16 !=3D 0)
+  ivtmp_32 =3D ivtmp_33 - 1;
+  if (ivtmp_32 !=3D 0)
```
The only thing I can of which might be causing the issue is +255 vs -1 here=
.=