[Bug fortran/31732] [4.3 regression] Assignment to array slice affects whole array

["tkoenig at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from tkoenig at gcc dot gnu dot org  2007-04-28 11:23 -------
The zeroing is done by memset, as the slightly reduced test case shows:

$ cat test2.f90
program Test
  implicit none
  real, dimension (2,2) :: smooth_factor
  data smooth_factor /4*1.0/

  smooth_factor(1,:) = 0.
  print *, smooth_factor

end program
$ gfortran -fdump-tree-original test2.f90
$ ./a.out
   0.000000       0.000000       0.000000       0.000000
$ cat test2.f90.003t.original
MAIN__ ()
{
  static real4 smooth_factor[4] = {1.0e+0};

  _gfortran_set_std (68, 127, 0, 0, 0);
  (void) __builtin_memset ((void *) &smooth_factor, 0, 16);
  {
    struct __st_parameter_dt dt_parm.0;

    dt_parm.0.common.filename = "test2.f90";
    dt_parm.0.common.line = 7;
    dt_parm.0.common.unit = 6;
    dt_parm.0.common.flags = 128;
    _gfortran_st_write (&dt_parm.0);
    {
      struct array2_real4 parm.1;

      parm.1.dtype = 282;
      parm.1.dim[0].lbound = 1;
      parm.1.dim[0].ubound = 2;
      parm.1.dim[0].stride = 1;
      parm.1.dim[1].lbound = 1;
      parm.1.dim[1].ubound = 2;
      parm.1.dim[1].stride = 2;
      parm.1.data = (void *) &smooth_factor[0];
      parm.1.offset = 0;
      _gfortran_transfer_array (&dt_parm.0, &parm.1, 4, 0);
    }
    _gfortran_st_write_done (&dt_parm.0);
  }
}

This is probably a result from

2006-12-20  Roger Sayle  <roger@eyesopen.com>

        * trans-expr.c (is_zero_initializer_p): Determine whether a given
        constant expression is a zero initializer.
        (gfc_trans_zero_assign): New function to attempt to optimize
        "a(:) = 0.0" as a call to __builtin_memset (a, 0, sizeof(a));
        (gfc_trans_assignment): Special case array assignments to a
        zero initializer constant, using gfc_trans_zero_assign.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31732