[llvm-bugs] [Bug 50621] New: wrong code at -O2 on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50621

            Bug ID: 50621
           Summary: wrong code at -O2 on x86_64-linux-gnu
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: qrzhang at gatech.edu
                CC: llvm-bugs at lists.llvm.org, neeilans at live.com,
                    richard-llvm at metafoo.co.uk

It appears to be a recent regression.


$ clang-trunk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
61a2d6bfe48cf3da4b95d1383bf866690287f8e8)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin


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


$ clang-trunk -O2 abc.c ; ./a.out
1


$ cat abc.c
short b, e;
int c, d, g;
int f[] = {2, 6, 0, 4};
void(h)();
int main() {
  short a[] = {3, 2, 3};
  f[2] = h || b;
  for (; g <= 1; g++) {
    e = 3;
    for (; e; e--) {
      d = 1;
      if (a[g] < f[e])
        d = a[g + 1] = c;
      else
        break;
    }
  }
  printf("%d\n", d);
}

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