[llvm-bugs] [Bug 36229] New: wrong code at -Os and -O2 on x86_64-linux-gnu in 64-bit mode

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36229

            Bug ID: 36229
           Summary: wrong code at -Os and -O2 on x86_64-linux-gnu in
                    64-bit mode
           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 324184. 

$ clangpolly -v
clang version 7.0.0 (http://llvm.org/git/clang.git
6804b86ee9cc16b8a0dbc7024a497d179e88b4d4) (http://llvm.org/git/llvm.git
5a24493720154c8145652dd8d2dcee565bd50b99)
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 -O1 small.c; ./a.out
6
$ gcc-7.2.0 -Os small.c; ./a.out
6
$ 
$ clangpolly -Os small.c; ./a.out
0
$ 


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


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

int a, b, c, g, *h = &a;
char d, e = -1;
static int f;

char fn1 (char j, int k)
{
  return j < 0 ? j : j >> k;
}

int fn2 (int j)
{
  return j;
}

int main ()
{
  long m = 249;
  while (c--)
    {
      if ((d < 1) & fn2 (2))
        f++;
      if (g)
        break;
      if (f)
        b = --m;
    }
  *h = fn1 (m, 6) ^ e;
  printf ("%d\n", a);
  return 0; 
}

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