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

Michael Niedermayer michaelni
Thu Mar 15 03:52:50 CET 2007


Hi

On Thu, Mar 15, 2007 at 01:32:50AM +0000, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > Hi
> >
> > On Thu, Mar 15, 2007 at 12:44:03AM +0000, M?ns Rullg?rd wrote:
> >> 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?  
> >
> > i dont know what gcc does with PIC on x86-64 maybe it doesnt reserve
> > ebx/rbx after all theres no technical reason why it reserves it on
> > x86-32 it could just handle the extra indirection over the GOT table
> > like any other pointer dereference in C
> 
> Can you suggest some test we could do to find out?

assume ebx is always available on x86-64 and wait for bugreports ...

anyway i think zuxy is right that x86-64 uses rip relative addressing to
reach the GOT but then again thats just what should be done iam too
tired to use google to check if it actually is ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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