[Bug rtl-optimization/68194] New: wrong code at -O2 and -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68194

            Bug ID: 68194
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -O2
and -O3 in both 32-bit and 64-bit modes. 

This is a regression from 5.2.x.


$ 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/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20151101 (experimental) [trunk revision 229639] (GCC) 
$ 
$ gcc-trunk -Os small.c; ./a.out
0
$ gcc-5.2 -O2 small.c; ./a.out
0
$ 
$ gcc-trunk -O2 small.c
$ ./a.out
-16
$ 


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


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

int a, c, d, e, g, h;
short f;

short
fn1 () 
{
  int j[2];
  for (; e; e++)
    if (j[0])
      for (;;)
        ;
  if (!g)
    return f;
}

int
main ()
{
  for (; a < 1; a++)
    {
      for (c = 0; c < 2; c++)
        { 
          d && (f = 0); 
          h = fn1 (); 
        }
      printf ("%d\n", (char) f);   
   }

 return 0;
}