[Bug tree-optimization/93820] New: wrong code at -O3 on x86_64-linux-gnu

[qrzhang at gatech dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93820

            Bug ID: 93820
           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 to be a regression in 9.x. Gcc-8.3 works fine.

Bisection points to:  g:be43a8877e2f2f4590ba667b27a24a0cfdf8141d



$ gcc-trunk -v
gcc version 10.0.1 20200218 (experimental) [master revision
da67227bfc4:72b83cccb06:d4c10c9f4bff616e7ed07e92504fe31a700e2af1] (GCC)

$ gcc-trunk -O3 abc.c ; ./a.out
1
$ gcc-trunk abc.c ; ./a.out
0


$ cat abc.c
int printf(const char *, ...);
int a[10];
int b, d, h;
int *c = &b, *g;
short e;
int **f;
int ***i = &f;
void k() {
  e = 5;
  for (; e; e--) {
    a[e + 4] = *c;
    a[e + 2] = 0 != &d;
  }
  char j;
  b = 0;
  for (; b <= 5; b++) {
    j = 0;
    for (; j <= 5; j++)
      a[j + 3] = 0;
  }
  for (;;) {
    *i = &g;
    *f = &h;
    if (**i)
      break;
    int l = 9;
    for (; l; l--)
      a[l] = 0;
  }
}
int main() {
  k();
  printf("%d\n", a[4]);
}