Re: I found a FORTH stack optimzer, but could use a better version.

On Fri, 11 Jan 2008 08:34:02 -0000, Rod Pemberton  
<do_not_have@[EMAIL PROTECTED]
> wrote:

> "Jenny Brien" <jennybrien@[EMAIL PROTECTED]
> wrote in message
>
news:ab815318-9e67-4709-a479-a5fdae1bd429@[EMAIL PROTECTED]
>> I'm interested in the minimal set needed to implement the normal Forth
>> stack operators.
>
> Then these might be of use which use rstack:
>
I'm thinking more of minimal hardware requirement in terms of registers  
and opcodes. I know that it's /possible/ to do any manipulation with just 

the two stacks and a single register, but it's not very efficient.

>> Since I shall need an rstack anyway, I think adding
> that to Chapman's quarks might be a reasonable compromise.
>
The fastest code needs at least n+1 registers or stacks to re-sort n  
items. If all were are on the hardware stack to begin with then 2SWAP  
would take 8 moves (pop all to registers, push all back in order), reduced
 
to 6 with the top two items cached. Using a second stack instead of  
multiple registers hurts more than I thought at first; using my rcheme I  
cannot implement 2SWAP in fewer than 13 moves.