Re: Code Generation Question

["Jeff Creem" <jeff@thecreems.com>]

This is very common especially in custom hardware.

In any case the best approach for anything like this is to
have a package that encapsulates all read/write access to the hardware. Once
that is setup, assuming it is complete, you will almost never be modifying
that package.

Leaving scattered access to hardware in many places is just asking for
trouble.

"Charles H. Sampson" <claveman@cod.nosc.mil> wrote in message
news:98ug7e$9oj$1@newpoisson.nosc.mil...
>      This is not strictly an Ada issue but, since this group has one of
> the best signal to noise ratios in USENET, I'll post it here anyhow.  In
> my defense, it did arise in an Ada project that I'm currently working
> on.
>
>      Our project uses a heavily populated VME rack with a PowerPC as the
> CPU.  I certainly don't understand all of the VME arcania but it seems
> obvious to me that VME is at its root byte oriented.  One of the cards
> in the rack requires 16-bit reads and writes to its memory.  If you at-
> tempt an 8-bit read or write there is no indication of error; instead
> the board silently zeros the other byte of the 16-bit word.
>
>      This causes quite a bit of problem, as you might guess when you re-
> flect on it for a minute.  Whenever the module is modified (fortunately,
> it's now pretty stable), we have to investigate the code generated by
> the compiler to verify that there are no byte reads or writes to the
> board's memory.  If there are, we have to figure out a way to trick the
> compiler into not doing it.
>
>      I consider this wildly unreasonable.  My question is this: Are
> there compilers, for any language, that give the user the ability to
> subset the hardware instruction set used for a compilation?  I don't
> know of any and I've had experience with 20-30 compilers in my career.
> Other people, particularly those in academic settings, might have seen
> many more.
>
>                     Charlie
>
>
> --
> ******
>
>      For an email response, my user name is "sampson" and my host
> is "spawar.navy.mil".