[Bug tree-optimization/79286] New: wrong code at -O3 on x86_64-linux-gnu in 32-bit mode (but not in 64-bit mode)

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79286

            Bug ID: 79286
           Summary: wrong code at -O3 on x86_64-linux-gnu in 32-bit mode
                    (but not in 64-bit mode)
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

This seems to be a recent regression. 

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/7.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 7.0.1 20170130 (experimental) [trunk revision 245020] (GCC)
$
$ gcc-trunk -m32 -O2 small.c; ./a.out
$ gcc-trunk -m64 -O3 small.c; ./a.out
$
$ gcc-trunk -m32 -O3 small.c
$ ./a.out
Segmentation fault (core dumped)
$


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


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

int a[6], b, c, d, e, f, g, h;
static int i[][8] = { { 0 } };

void fn1 (int l)
{ 
  c = (c & 5) ^ a[(c ^ l) & 5];
}

void fn2 ()
{ 
  fn1 (e >> 5);
  fn1 (e >> 6 & 5);
  c = (c & 5) ^ a[(c ^ 5) & 5];
  fn1 (e >> 2 & 5);
  fn1 (e & 5);
  fn1 (e >> 28 & 5);
}

void fn3 ()
{ 
  int k;
  for (; g < 4; g++)
    { 
      while (d)
        { 
          fn2 ();
          if (k)
            printf ("%d\n", k);
        }
      while (f)
        while (h++)
          k = i[300000000000000000][0];
      while (b)
        while (1)
          d++;
    }
}

int main ()
{ 
  fn3 ();
  return 0;
}