[llvm-bugs] [Bug 49584] New: wrong code at -Os and above on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49584

            Bug ID: 49584
           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: Interprocedural Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: zhendong.su at inf.ethz.ch
                CC: llvm-bugs at lists.llvm.org

[524] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
2b3c8131434374caf3825c2bd4e012c85f8128de)
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
[525] % 
[525] % clangtk -O1 small.c; ./a.out
[526] % 
[526] % clangtk -Os small.c
[527] % ./a.out
Floating point exception
[528] % 
[528] % cat small.c
static int a(int b, int c) { return c && b < 1 / c; }

int d, e, f[7], g, h;

void j(int **k) {
  int *m = &g, i = 0;
  for (; i < 6; i++)
    if (h) {
      int *n = &d;
      for (; i < 9; i++)
        *n = 1;
    }
  if (a(**k, &f[6] == m))
    e = 0;
}
int main() {
    int *o = &d, *p = &d;
    *o = 0;
    j(&p);
    return 0;
}

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