Re: Compilers

[Mark Junker <mjscod@gmx.de>]

Eduardo Pereira Habkost schrieb:

> 
> _fnord:
>         push    %bp
>         mov     %sp,%bp
> 
>         movw    2(%bp),%dx
should be "movw    4(%bp),%dx"

>         movw    $0x0,%ax
>         cmpw    $0x0,%dx
>         je      .L15
> .L13:
>         addw    %dx,%ax
>         addw    $0xffffffff,%dx
should be:
addw    $0xffff,%dx

$0xffffffff is a 32 bit constant

>         cmpw    $0x0,%dx
>         jne     .L13
> .L15:
> 
>         leave
"leave" is only available on 186+

>         ret
> 
> Some things that can be noted: There is not 'dec' instruction, yet. It
> can be added. It is using 'leave' for function exit. IIRC, it is a
> 80186 instruction, so it is better have an option to use is better have
> an option for the user choosing to use it or not.
You're right.

> One bug appeared: it is using 2(%bp) for getting the function
> parameter. It doesn't look correct.  :)
Again, you're right. It's not correct

> A -fno-frame-pointer option would be nice, too. I guess that most people
> wouldn't want them on ELKS, and it will make code smaller and use less
> stack space.
This can (sometimes) produce smaller code.

Regards,
Mark Junker