[llvm-bugs] [Bug 28824] New: wrong code (segfault) at -O3 on x86_64-linux-gnu in the 32-bit mode

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28824

            Bug ID: 28824
           Summary: wrong code (segfault) at -O3 on x86_64-linux-gnu in
                    the 32-bit mode
           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 277497)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/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
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
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/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
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/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.1.1
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 -m32 -O2 -w small.c; ./a.out
$ clang-3.8 -m32 -O3 -w small.c; ./a.out
$
$ clang -m32 -O3 -w small.c
$ ./a.out
Segmentation fault (core dumped)
$


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


struct
{ 
  int f0;
} a = {1}, b;

volatile int c;
int d, e, f, g, h, i, j, k, l, m[1], n, o, p, q, r[1], s, t, u;

void fn1 (int p1)
{ 
  n = n >> 8 ^ m[n ^ p1];
}

void fn2 ()
{ 
  fn1 (l > 0);
  fn1 (l >> 8);
  fn1 (l & 5);
  n = n >> 8 ^ n;
}

static void fn3 (int p1, int p2, int p3, short p4)
{ 
  q = q && (p1 = p4);
  for (; o; o++)
    { 
      h = e ? 0 : s;
      g = j;
      s = p2 | (p3 == (f < h)) | j;
      if (p1)
        c;
    }
}

int fn4 ()
{ 
  short v, x = i;
  fn2 ();
  v = x >> d;
  fn3 (2, 5, v, i);
  fn3 (4, 0, 0, p);
  if (v < 1)
    return t;
  a = b;
  return 0;
}

int fn5 ()
{ 
  for (; i < 2; i++)
    fn4 ();
  if (!a.f0)
    return u;
  k = r[2000];
  return 0;
}

int main ()
{ 
  fn5 ();
  return 0;
}

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