[Bug rtl-optimization/70005] 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=70005

            Bug ID: 70005
           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 5.3.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-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 6.0.0 20160228 (experimental) [trunk revision 233789] (GCC) 
$ 
$ gcc-trunk -Os small.c; ./a.out
$ gcc-5.3 -O2 small.c; ./a.out
$ 
$ gcc-trunk -O2 small.c
$ ./a.out
Aborted (core dumped)
$ 


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


unsigned char a = 6;
int b, c;

static void
fn1 ()
{
  int i = a > 1 ? 1 : a, j = 6 & (c = a && (b = a));
  int d = 0, e = a, f = ~c, g = b || a;
  unsigned char h = ~a;
  if (a)
    f = j;
  if (h && g)
    d = a;
  i = -~(f * d * h) + c && (e || i) ^ f;
  if (i != 1) 
    __builtin_abort (); 
}

int
main ()
{
  fn1 ();
  return 0; 
}