[llvm-bugs] [Bug 49661] New: wrong code at -O2 and -O3 on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49661

            Bug ID: 49661
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: zhendong.su at inf.ethz.ch
                CC: llvm-bugs at lists.llvm.org

[520] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
f860187ea6e9b30e1ecf74784f0af0e0c9ecc01c)
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
[521] % 
[521] % clangtk -Os small.c; ./a.out
[522] % 
[522] % clangtk -O2 small.c
[523] % ./a.out
Segmentation fault
[524] % 
[524] % cat small.c
static int *a[2][3][3], b, c;
int main() {
  for (c = 0; c < 2; c++)
    for (b = 0; b < 2; b++)
      a[1][c][b] = a[0][0][0];
  return 0;
}

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