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

[Aurelien Jacobs]

On Thu, 15 Mar 2007 01:15:32 +0100
Michael Niedermayer <michaelni at gmx.at> wrote:

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

Theoretically, the frame pointer check should be done on rbp instead of ebp.
But IIRC when you set the lower 32 bits of a register, the higer 32 bits are
cleared to 0. So the frame pointer check will probably work on x86_64 as is.

Aurel