[llvm-bugs] [Bug 25908] New: wrong code on x86_64-linux-gnu at -O3 in both 32-bit and 64-bit modes

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=25908

            Bug ID: 25908
           Summary: wrong code on x86_64-linux-gnu at -O3 in both 32-bit
                    and 64-bit modes
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: chengniansun at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

$: clang-trunk -v
clang version 3.8.0 (trunk 256125)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.2.1
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/5.2.1
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.6.3
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.7.4
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.8.2
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-trunk small.c -w -O3 -m64 ; ./a.out
0
Segmentation fault (core dumped)
$: clang-trunk small.c -w -O3 -m32 ; ./a.out
0
Segmentation fault (core dumped)
$: clang-trunk small.c -w -O0 ; ./a.out
0
$:
$:
$: cat small.c
int printf(const char*, ...);
int a, c, d, e, g, i, j;
volatile int b;
volatile short f = 5;
volatile char h;
short o;
void fn1() {
  while (i)
    ;
  short k = f && h % 5;
  int l = ~j % f;
  short m = ~j & k;
  int n = 5 % ~h;
  g = f | 1 && m ^ l | n;
}

static short fn2() {
  int p = 3;
  for (; p >= 0; p--) {
    o = 0;
    for (; o <= 3; o++) {
      d = 0;
      for (; d <= 3; d++)
        b &= 5;
    }
    if (e)
      break;
  }
  return 1;
}

static int fn3() {
  c = 0;
  for (; c <= 3; c++) {
    fn2();
    fn1();
    e = 0;
  }
  return 1;
}

int main() {
  fn3();
  printf("%X\n", a);
  return 0;
}

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