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Re: Rep:Re: Rep:Re: [f-cpu] Stack handling
I'm not against having a separate stack for data in one hand and the return
addresses in other hand. But I'm not sure the huge dependency is really
alleviated for the data (since they are the main part of what is pushed).
Maybe using two stack registers in parallel to push data can divide this
dependency :
to push r1..r6, do :
addi -8 ,r62,r8
store -16,r62,r1
store -16,r8 ,r2
store -16,r62,r3
store -16,r8 ,r4
store -0 ,r62,r5
store -0 ,r8 ,r6
instead of :
store -8,r62,r1
store -8,r62,r2
store -8,r62,r3
store -8,r62,r4
store -8,r62,r5
store -0,r62,r6
why not a triple stack ?
addi -8 ,r62,r8
addi -16,r62,r9
store -24,r62,r1
store -24,r8 ,r2
store -24,r9 ,r3
store -0 ,r62,r4
store -0 ,r8 ,r5
store -0 ,r9 ,r6
----- Original Message -----
From: "Nicolas Boulay" <nicolas.boulay@ifrance.com>
To: <f-cpu@seul.org>
Sent: Tuesday, July 23, 2002 4:27 PM
Subject: Rep:Re: Rep:Re: [f-cpu] Stack handling
Stack have a main draw back : it's add a udge dependancies in a single
poor register (the stack pointer).
For security reason, i have proposed to use 2 stack : one for data, one
for code. So buffer overflow will became really hard ! this could be
usefull for performance, too. But most of the time, the stack will use
the register bank...
And that doesn't solve the problem of push and pop.
nicO
-----Message d'origine-----
De: Thomas Lavergne <thomas.lavergne@laposte.net>
A: f-cpu@seul.org
Date: 23/07/02
Objet: Re: Rep:Re: [f-cpu] Stack handling
Have you ever written a compiler ?
A stack is the most simple and clean solution to handle a lot of thing.
We have a lot of register so most compiler simulate the first stack
push/pop with reg but when the stack grow we need a real stack handling.
If we haven't stack we must reinvent the weel or back 50 years ago in
compiler theorie.
The debat about the number of stack is another thing, I think we need
some instruction for stack (pre-dec) on all register so we can have all
stack we need.
Juergen Goeritz wrote:
> No, it's not a stupid question at all. I had the same
> first thought when I read the posting. You may just
> have a need for a seperate stack for the scheduling
> handler.
>
> JG
>
>
> On Tue, 23 Jul 2002, Nicolas Boulay wrote:
>
>>Maybe it's a stupid question, but why it's forced to try to simulate a
>>simple stack. There is no hardware support for stack in the f-cpu. Why
>>not using a completely different pointer for such things ? Why must we
>>stuck to the use of one single stack ?
>>
>>nicO
>>
--
Thomas Lavergne "Le vrai rêveur est celui qui rêve
de l'impossible." (Elsa
Triolet)
thomas.lavergne@laposte.net
d-12@laposte.net ICQ:#137121910 http://assoc.wanadoo.fr/thallium/
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