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From: "qrzhang at gatech dot edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/101885] New: wrong code at -O3 on
 x86_64-linux-gnu
Date: Thu, 12 Aug 2021 17:09:49 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101885

            Bug ID: 101885
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: qrzhang at gatech dot edu
  Target Milestone: ---

It appears a regression in gcc-10. gcc-9 works fine.


$ gcc-trunk -v
gcc version 12.0.0 20210812 (experimental) [master revision
01f8a8b48e5:0eb7800d242:04b4f3152593f85b05974528d1607619dd77d702] (GCC)


$ gcc-trunk abc.c ; ./a.out
0

$ gcc-trunk -O3 abc.c ; ./a.out
3


$ cat abc.c
int a =3D 3, c;
short b =3D 5, d, f;
volatile short e;
int main() {
  f =3D 29;
  for (; f !=3D 33; f++) {
    int g =3D a;
    if (b)
      if (a) {
        a =3D b =3D 0;
        for (; b <=3D 8; b++)
          ;
      }
    e;
    e;
    c =3D 0;
    for (; c !=3D 14; ++c)
      e;
  }
  b =3D d;
  printf("", 8);
  printf("%d\n", a);
}=