[Ffmpeg-devel] [BUG] Compilation failure when using --disable-opts

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> Hi
>
> On Thu, Mar 15, 2007 at 12:13:07AM +0000, M?ns Rullg?rd wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> 
>> > Hi
>> >
>> > On Wed, Mar 14, 2007 at 10:16:59PM +0000, M?ns Rullg?rd wrote:
>> >> Panagiotis Issaris <takis at issaris.org> writes:
>> > [...]
>> >> >> And are you certain that this is correct for x86_64?  Is the check
>> >> >> even needed there, what with all the extra registers?
>> >> > Actually, I do not really know... I figured that because x86_64 is
>> >> > backwards compatible
>> >> 
>> >> The instruction set is compatible, meaning that everything that works
>> >> on 32-bit x86 still works on a 64-bit chip.  Things that don't work on
>> >> 32-bit chips might still be possible.  8 extra registers come to
>> >> mind...
>> >> 
>> >> > the registers are still there and the tests should still work. In the
>> >> > worst case the tests would be unnecessary ofcourse... Prefer to remove
>> >> > it and only add it when someone figures out how this works on x86_64?
>> >> 
>> >> I don't think this is very urgent, so I'd rather wait a day for
>> >> someone with the knowledge to shed some light.
>> >
>> > the tests should be run on x86_64 too
>> 
>> Care to explain? 
>
> well if the x86 code is put under a CONFIG_EBX which is never set
> for x86_64 then you practically disable it for x86_64, not nice ...

What I meant was, is ebx ever reserved the same way on x86_64?  With 8
more registers, it seem to me there should be enough for both a frame
pointer and whatever registers the inline asm needs.  Even if ebx is
reserved, some other register could be used by the assembler code.

>> Does the same test even work at all on x86_64?
>
> why not?

Some things are done differently on x86_64.  I didn't know, and still
don't, whether the stack/frame pointer is one of them.

-- 
M?ns Rullg?rd
mans at mansr.com