Re: Optimizing Boundary Checks

[Vinzent Hoefler <ada.rocks@jlfencey.com>]

Martin Dowie wrote:

>Keyword in the last line is 'can'. I've run across compilers that
>will do no optimization (i.e. leave checks in) on code such as:
>
>   for I in My_Type loop
>      Make_Call(My_Array (I));
>   end loop;
>
>but would take them out if written:
>
>   for I in My_Array'Range loop
>      Make_Call(My_Array(I));
>   end loop;

This I find interesting. (Of course, assuming that My_Type is the
Index type of My_Array).

>Not sure if the checks in the first example would have
>disappeared if we'd been allowed to switch compiler
>optimizations on...

I'd guess so.

>I guess the you just have to get that assembler listing and
>check what each compiler you use does!

Yes. I'd say, the only thing we know is where the compiler is required
to do range checks, not where it is permitted to suppress them.


Vinzent.