[Vm-dev] 64bit FFI?

Eliot Miranda eliot.miranda at gmail.com
Thu Feb 12 19:01:02 UTC 2009


On Thu, Feb 12, 2009 at 10:59 AM, Andreas Raab <andreas.raab at gmx.de> wrote:

>
> Eliot Miranda wrote:
>
>> Um, I have (studied my Agrippa), and I quote:
>>
>> Does my 64-bit VM run both 32-bit and 64-bit images?
>>    No. Any VM will run either 32-bit or 64-bit images, but not both.
>>
>
> This is a bit misleading. What it means is that once you've decided whether
> a 64 bit VM will be used with 32 or 64 bit images, you cannot change it.
> However, 64 bit VMs can absolutely be used to run 32 bit images (and why
> wouldn't they).


I'm assuming that in-memory the 64-bit VM has 64-bit oops, right?  So the VM
has to swizzle 32-bit pointers to 64-bit.  I haven't come across this
swizzling code yet.  I thought that the swizzling was done by the system
tracer.  Where is the in-VM code to swizzle pointers to 64-bits?

>
>
> Cheers,
>  - Andreas
>
>
>
>     You can select one or the other when you generate sources with
>>    VMMaker, and you can install both flavors of VM on your system (one
>>    each for 32-bit images and 64-bit images).
>>
>>    If you try to run a 64-bit image with a VM built for 32-bit images,
>>    you will get an error message such as this:
>>
>>        This interpreter (vers. 6502) cannot read image file (vers. 68000).
>>
>>    If you try to run a 32-bit image using a VM built for 64-bit images,
>>    you will get an error message such as this:
>>
>>        This interpreter (vers. 68000) cannot read image file (vers. 6502).
>>
>>
>> So no, one cannot run a 32-bit image in a 64-bit VM (as I had thought) and
>> the FAQ is quite specific about it.  One has to convert a 32-bit image to a
>> 64-bit image to run it on the 64-bit machine (as detailed ijn the FAQ) and
>> that is not what Andreas is interested in doing.
>>
>> Apologies for being so persistent :)
>>
>>
>>
>>        http://squeakvm.org/squeak64/faq.html
>>
>>
>>
>>    - Bert -
>>
>>
>>
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