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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	[thread overview]
Message-ID: <bug-110582-4-Y4TT5Hfhmh@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110582-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110582

--- 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 = a = 0;
  unsigned char t = 253;
  for (; t != 0; t --){
    int d = 2;
    d ^= 2 && a;
    b = a == 0 ? d : d / a;
    a = 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 = PHI <t_16(5), 253(2)>
   # .MEM_20 = PHI <.MEM_20(5), .MEM_11(D)(2)>
   # a_lsm.11_2 = PHI <iftmp.1_9(5), 0(2)>
+  # ivtmp_33 = PHI <ivtmp_32(5), 253(2)>

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

  parent reply	other threads:[~2023-07-08  1:08 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-07  8:03 [Bug c/110582] New: " shaohua.li at inf dot ethz.ch
2023-07-07  8:40 ` [Bug tree-optimization/110582] [14 Regression] " pinskia at gcc dot gnu.org
2023-07-07 11:19 ` rguenth at gcc dot gnu.org
2023-07-08  1:08 ` pinskia at gcc dot gnu.org [this message]
2023-07-08  1:17 ` pinskia at gcc dot gnu.org
2023-07-30 14:46 ` shaohua.li at inf dot ethz.ch
2023-07-31 16:06 ` cvs-commit at gcc dot gnu.org
2023-07-31 16:11 ` amacleod at redhat dot com

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