[llvm-bugs] [Bug 37826] New: wrong code at -O2 on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37826

            Bug ID: 37826
           Summary: wrong code at -O2 on x86_64-linux-gnu
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvm-bugs at lists.llvm.org

Tested with trunk revision 334906. 

$ clangpolly -v
clang version 7.0.0 (http://llvm.org/git/clang.git
c36069cffc57a30a20782bf327a87bed4e48a6c2) (http://llvm.org/git/llvm.git
59cb663e72874dda740aa2b18bf47ba65b32fe9b)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/su/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$ 
$ clangpolly -Os small.c; ./a.out
 0
$ 
$ clangpolly -O2 small.c; ./a.out
 262143
$ 


--------------------------------------


int printf (const char *, ...);

struct
{
  unsigned a:21;
  unsigned b:24;
} c = { 8, 0 }, f;

int d, e, g, j;
static int h;

void k (int l)
{
  int m = 4, i = 0;
  for (; i < 9; i++)
    while (d > 6)
      {
        int n;
        if (h)
          break;
        m = 1;
      }
  while (1)
    {
      printf (" ");
      if (m)
        {
          g = c.a;
          j = f.b;
          c.a = ~f.b;
          f.b = (9 | c.a / g) ^ e;
        }
      c.a = g;
      f.b = j;
      int o = 0;
      if (l)
        break;
      if ((l >= 0) == o)
        h = 4;
    }
}

int main ()
{
  k (1);
  printf ("%d\n", f.b);
  return 0;
}

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