[llvm-bugs] [Bug 50947] New: wrong code at -Os and above on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50947

            Bug ID: 50947
           Summary: wrong code at -Os and above on x86_64-linux-gnu
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Transformation Utilities
          Assignee: unassignedbugs at nondot.org
          Reporter: zhendong.su at inf.ethz.ch
                CC: llvm-bugs at lists.llvm.org

Here is another recent regression which appears unrelated to
https://bugs.llvm.org/show_bug.cgi?id=50944.

[564] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
0c96a92d8666b8eb69eb1275aed572f857182d9a)
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
[565] % 
[565] % clangtk -O1 small.c; ./a.out
[566] % 
[566] % clangtk -Os small.c
[567] % ./a.out
Aborted
[568] % 
[568] % cat small.c
int a[36], b, c, d, e, f;
int main() {
  for (c = 0; c < 6; c++)
    for (d = 0; d < 6; d++)
      for (b = 0; b < 6; b++)
        a[6 + c] = a[c * 6 + c] ^ 1;
  if (a[7] != 0)
    __builtin_abort ();
  return 0;
}

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