[FFmpeg-devel] r9017 breaks WMA decoding on Intel Macs

Michael Niedermayer michaelni
Fri Jun 1 01:09:55 CEST 2007


On Thu, May 31, 2007 at 03:39:43PM -0700, Trent Piepho wrote:
> > to summarize the possible solutions
> > 1. dont support ancient assemblers
> > 2. use 123%4 notation (most incorrect syntax possible, and will silently
> >    generate wrong code on all assemblers if you are unlucky)
> > 3. add more "m" operands to avoid the offsets (might be slower, and might
> >    fail on some gcc versions)
> "might"

yes might ...

> > 4. write the whole loop in asm
> >
> > note, ALL solutions need a "memory" clobber (or some other nasty tricks)
> If you cast the operands through a struct that's 64-bits/128-bits as
> apporpriate then you don't need to memory clobber.

= nasty tricks ...
also these can be done with the current controversal 123+%4 code as well

so i think you will agree with me that gcc does not gain any knowledge
of the read/written memory locatons by introducing extra operands in this
case ...

and in the case that you agree we are back to the original:
current code (breaks old buggy apple assembler) vs. more operands which might
break with old gcc vs. writing the loop in asm which will be faster,
more compatible and wont depend on the moon phases when gcc was

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable
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