[llvm-bugs] [Bug 50587] New: wrong code at -O3 on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50587

            Bug ID: 50587
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: zhendong.su at inf.ethz.ch
                CC: llvm-bugs at lists.llvm.org

[611] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
92ce29ee45b26513a9f4e42c6f287f43cb3de238)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /local/suz-local/opfuzz/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
[612] % 
[612] % clangtk -O2 small.c; ./a.out
[613] % 
[613] % clangtk -O3 small.c
[614] % ./a.out
Aborted
[615] % 
[615] % cat small.c
int a, b, c;
void f() {
  int d = 1, e = 1;
  while (1)
    for (; c < 1; c++) {
      if (!d && e)
        continue;
      if (a < 1) {
        if (e)
          b++;
        return;
      }
      d = 0;
      while (b)
        e++;
    }
}
int main() {
  f();
  if (b != 1)
    __builtin_abort ();
  return 0;
}

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