[Ffmpeg-devel] [PATCH] Machine endian bytestream functions

Michael Niedermayer michaelni
Tue Apr 24 02:49:12 CEST 2007


On Tue, Apr 24, 2007 at 01:37:11AM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> > Hi
> >
> > On Sat, Apr 14, 2007 at 12:21:20AM +0100, M?ns Rullg?rd wrote:
> > [...]
> >> >> I'm thinking the unaligned16/32/64 macros from bitstream.h should be
> >> >> renamed and moved here instead.
> >> >>
> >> > I'll take a look.
> >> 
> >> This lets the compiler choose whatever access method is appropriate,
> >> and saves us the trouble of maintaining a fragile list.
> >
> > iam not sure what exactly you are proposing
> >
> > the compiler does not know if bytewise read is faster then unaligned
> > uintXY_t read with a user provided (possibly asm) bswap afterwards
> The compiler knows if unaligned access is possible at all. It may
> also know ways of accessing unaligned data that are faster than
> reading 4 bytes but slower than aligned access.  The bswap reference
> seems completely out of place here.  The macros we're talking about
> are for reading native endian data.

the patches posted in this thread which should have been applied add 
unaliged read with bswap they dont change the native endian functions

> > also with the argument that the compiler should know what is best we can
> > rm -r i386/ ppc/ alpha/ ...
> Don't be stupid.  When you say things like that I get the feeling
> you've run out of arguments.  Or possibly forgotten what you were
> arguing.

thank you to remind me who has run out of arguments, i almost thought
it was someone else

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
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