flac dev - Feb 2005 - A couple of points about flac 1.1.1 on ppc/linux/altivec

Josh Coalson <xflac@yahoo.com> writes:
> --- John Steele Scott <toojays@toojays.net> wrote:
>> Back in October 2004, I did a bit of work on FLAC to get version
>> 1.1.1 to
>> build correctly under GNU/Linux/PPC. Only now have I realised that
>> somewhere
>> along the way something broke in FLAC's decoding. On my machine,
>> roughly 50%
>> of FLAC files are being decoded incorrectly.
>> 
>> I presume that I broke the code somehow when translating Josh's
>> original OS X
>> assembler into GNU style.
>
> are you the one who submitted the patch with a translated
> version of lpc_asm.s?  I thought that was Luca.
I'm not sure exactly what happened. What you have in CVS:
<http://cvs.sourceforge.net/viewcvs.py/flac/flac/src/libFLAC/ppc/gas/lpc_asm.s?rev=1.1&view=log>

is not the same as the patch applied by Gentoo:
<http://www.gentoo.org/cgi-bin/viewcvs.cgi/media-libs/flac/files/flac-1.1.1-altivec.patch.gz>

There is little difference between either version except for the comment
style, and the way constant addresses are specified. Also the Gentoo patch
patches cpu.c, otherwise the Altivec code path isn't taken.

I'm trying to get a handle on where I should be looking to fix the problem.
If
your saying that the gas version in FLAC CVS has been validated, the easiest
solution is to just use that one. Otherwise I need to go back to the Apple
version. Presumably that one has been thouroughly checked?

cheers,

John
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--- John Steele Scott <toojays@toojays.net> wrote:
> Josh Coalson <xflac@yahoo.com> writes:
> 
> > --- John Steele Scott <toojays@toojays.net> wrote:
> >> Back in October 2004, I did a bit of work on FLAC to get version
> >> 1.1.1 to
> >> build correctly under GNU/Linux/PPC. Only now have I realised that
> >> somewhere
> >> along the way something broke in FLAC's decoding. On my
machine,
> >> roughly 50%
> >> of FLAC files are being decoded incorrectly.
> >> 
> >> I presume that I broke the code somehow when translating
Josh's
> >> original OS X
> >> assembler into GNU style.
> >
> > are you the one who submitted the patch with a translated
> > version of lpc_asm.s?  I thought that was Luca.
> 
> I'm not sure exactly what happened. What you have in CVS:
>
<http://cvs.sourceforge.net/viewcvs.py/flac/flac/src/libFLAC/ppc/gas/lpc_asm.s?rev=1.1&view=log>
> 
> is not the same as the patch applied by Gentoo:
>
<http://www.gentoo.org/cgi-bin/viewcvs.cgi/media-libs/flac/files/flac-1.1.1-altivec.patch.gz>
> 
> There is little difference between either version except for the
> comment
> style, and the way constant addresses are specified. Also the Gentoo
> patch
> patches cpu.c, otherwise the Altivec code path isn't taken.
the one I checked I thought I got directly from Luca on this
list.  but I have lost track...
> I'm trying to get a handle on where I should be looking to fix the
> problem. If
> your saying that the gas version in FLAC CVS has been validated, the
> easiest
> solution is to just use that one. Otherwise I need to go back to the
> Apple
> version. Presumably that one has been thouroughly checked?
no, not yet, I haven't got to the point of straightening anything
out totally.

I know this is bad, but can I ask you guys (John/Luca/Chris) to
take a look at the latest CVS and try to get this working?  the
PPC improvements are very important for macs and Chris has a lot
of optimizations that have been backing up since I can't sort
things out.

the main problem is that the asm syntax for 'as' (the one from
apple that ships with darwin) and 'gas' are apparently different.
it sounds like for ppc-linux to work, there has to be a 'gas'
version.  all I have is an ibook that I don't want to mess with
too much so for me to do any work on it there has to be an 'as'
version as well.

since I don't know how to resolve this, in current CVS I have
checked in a system where there are src/libFLAC/ppc/as and
src/libFLAC/ppc/gas selected by configure.  I have also checked
in as many patches as I could make sense of (the cpu.c detection
stuff and the configure.in stuff).  can you guys take a look at
current CVS and help me get something that will build both ways?
after that it will be much easier for me to start looking at
correctness.

thanks,
Josh


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Josh Coalson wrote:
> since I don't know how to resolve this, in current CVS I have
> checked in a system where there are src/libFLAC/ppc/as and
> src/libFLAC/ppc/gas selected by configure.  I have also checked
> in as many patches as I could make sense of (the cpu.c detection
> stuff and the configure.in stuff).  can you guys take a look at
> current CVS and help me get something that will build both ways?
> after that it will be much easier for me to start looking at
> correctness.
There is a problem: the AC_CHECK_PROGS() just tests existence and I'm 
afraid both osx and linux/ppc have both as and gas executables.
running the configure as is will always turn on the "as" path.
--with-gas doesn't work to force it.
Probably a version check could help.

If you need access to a ppc linux box I could provide you an account on 
the pegII box I have at home, it isn't alwasy reachable since I didn't 
managed to set up a dyndns yet so you need to contact me (irc on freenode).

Regards

lu



-- 
Luca Barbato
Developer (Gentoo/linux)	/	Operational Manager (Gentoo/ppc)
Gentoo Linux				http://www.gentoo.org/~lu_zero