Re: Joint Strike Fighter

[Jeffrey Carter <jeffrey.carter@boeing.com>]

Marin David Condic wrote:
> 
> I would think that a sensible implementation of Ada would look at the size
> of the item being passed and decide on the most efficient means for the
> given architecture. AFAIK, the in/out-ness of a parameter shouldn't force a
> pass-by-value (the language lawyers can correct me here) but pretty
> definitely an "in out" ought to be able to go by reference. (Again presuming
> that the compiler makes an intelligent choice about how to pass the
> parameter for maximum efficiency.)

The ARM specifies that elementary types must be passed by value,
regardless of size or mode, and tagged and limited types must be passed
reference, regardless of size or mode. Other types are up to the
compiler writer.

So, for example, if your compiler supports 64-bit integer types on a
platform with 32-bit registers (as GNAT does), they must be passed by
value even though they don't fit in a single register and an address
does. In this case pass by reference might be more "efficient" but is
not allowed by the language.

On the other hand, a small limited type must be passed by reference even
though several of them might fit in one register. In this case pass by
value might be more "efficient" but again is not allowed.

-- 
Jeffrey Carter