Re: Pascal Calling Convention

["Randy Brukardt" <randy@rrsoftware.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccbp0xy5hu.fsf@shell01.TheWorld.com...
...
> Thanks for the clarification.  I agree with the above, and of course I
> agree that the stack doesn't have to be a contiguous block of memory.
> But why do you call that "contiguous stack" thing a "hardware stack"?
> I mean, on most architectures, push/pop are implemented by subtract/add
> instructions on the stack pointer register.  That's not a whole lot of
> "hardware support for stacks".  The hardware has instructions that
> support implementing arrays, and linked lists, too, but we don't call them
> "hardware arrays" or "hardware linked lists".
>
> OK, on x86, there are push/pop instructions.  But most stack
> manipulation is still just subtract/add.  Call pushes a return address.
> Enter/leave instructions are stack-oriented, but nobody uses those,
> because they're slow.  Maybe "the stack" on x86 could be called a
> "hardware stack", but it's pretty marginal in practice.

I can't speak for Keith, but most of the hardware architectures that I've 
worked on have had at least some architectual support for a "hardware" 
stack. Not only the Push/Pop instructions of the X86 for instance, but also 
the special SS stack segment register. The 68K also had a dedicated stack 
register and some special instructions for call/ret. Even the Unisys U2200 
mainframe had a stack segment and special instructions for call/ret and 
stack frames.

I agree that these things aren't that different than add or subtract, but 
given the way that they're documented (as a hardware-supported stack in each 
case), I think it is pretty obvious that these things exist. (Inventing your 
own terminology and ignoring the standard view of an architecture is a good 
way to confuse everyone who talks to you...)

                         Randy.