Re: Segments

MitchAlsup1 <mitchalsup@aol.com> schrieb:

On Tue, 7 Jan 2025 22:01:55 +0000, Thomas Koenig wrote:
>

MitchAlsup1 <mitchalsup@aol.com> schrieb:

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

WATFIV would catch a(9,11)

>
Every Fortran compiler I know has a bounds checking, but it is
optional for all of them. People still leave it off for production
code because it is too slow.
>
It would really be great if the performance degradation was
small enough so people would simply leave on the checks
for production code.  (Side question: What does CHERI
do with SIMD-vectorized code?)

>
How long does it take SW to construct the kinds of slices
a FORTRAN subroutine can hand off to another subroutine ??

For the snippet

subroutine bar
  interface
     subroutine foo(a)
       real, intent(in), dimension(:,:) :: a
     end subroutine foo
  end interface
  real, dimension(10,10) :: a
  call foo(a)
end

(which calls foo with an assumed-shape array) gfortran hands this
to the middle end:

__attribute__((fn spec (". ")))
void bar ()
{
  real(kind=4) a[100];

  {
    struct array02_real(kind=4) parm.0;

    parm.0.span = 4;
    parm.0.dtype = {.elem_len=4, .version=0, .rank=2, .type=3};
    parm.0.dim[0].lbound = 1;
    parm.0.dim[0].ubound = 10;
    parm.0.dim[0].stride = 1;
    parm.0.dim[1].lbound = 1;
    parm.0.dim[1].ubound = 10;
    parm.0.dim[1].stride = 10;
    parm.0.data = (void *) &a[0];
    parm.0.offset = -11;
    foo (&parm.0);
  }
}


The middle and back ends are then free to optimize.

That is a CHERRI capability that allows for access to every
even byte in a structure but no odd byte in the same structure ??