[llvm-bugs] [Bug 30448] New: wrong code at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes)

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30448

            Bug ID: 30448
           Summary: wrong code at -O3 on x86_64-linux-gnu (in both 32-bit
                    and 64-bit modes)
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

This is a regression from 3.8.x.


$ clang -v
clang version 4.0.0 (trunk 281848)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/bin
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/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.4
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/5.3.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$ 
$ clang-3.8.1 -O3 small.c; ./a.out
0
$ clang -O2 small.c; ./a.out
0
$ 
$ clang -O3 small.c  
$ ./a.out
1
$ 


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


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

int a, c, d = 8, e, f, g, h, l, k, m, n, o, p, q;
long b, r;
volatile long i;
long j[] = { 6069905 };

char fn1 (int p1, int p2)
{
  return p1 >> p2;
}

int fn2 (int p1)
{
  return p1;
}

static char fn3 (int p1, int p2)
{
  if (a)
  L1:
    if (!g)
      goto L2;
  for (o = 0; o < 2; o++)
    for (; p; p++)
      ;
  for (b = 3; b < 9; b++)
    {
      q = (n && (e = p2)) || r;
      for (; d; d--)
    for (r = 2; r < 9; r++)
      {
        if (p2)
          break;
        fn1 (7, p2) && (j[r] = 1);
      }
    }
  for (; p1 < 2;)
  L2:
    for (; f; g++)
      ;
  p2 && i;
  for (;; k++)
    {
      char s;
      for (; o;)
    {
      char t = 1 << c;
      c = t;
      if (t)
        goto L1;
      printf ("%d\n", h);
      p2 = 1;
      return n;
    }
    }
}

int main ()
{
  m = fn2 (38);
  fn3 (7, m);
  return 0;
}

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