[Bug rtl-optimization/69117] New: wrong code at -Os and above on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69117

            Bug ID: 69117
           Summary: wrong code at -Os and above 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 mis-compiles the following code on x86_64-linux-gnu at
-Os and above 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-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20160101 (experimental) [trunk revision 232023] (GCC) 
$ 
$ gcc-trunk -O1 small.c; ./a.out
$ gcc-5.3 -Os small.c; ./a.out
$ 
$ gcc-trunk -Os small.c
$ ./a.out
Aborted (core dumped)
$ 


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


int a, c, *d = &c, **e = &d, *g = &a;
static int ***b, **f = &d;

int
main ()
{
  **f = 0;
  int ****h = 0;
  if (c) 
    {
      *h = &e; 
      ***b = 0;
    }
  *e = g;

  if (d != &a)
    __builtin_abort ();

  return 0;
}