[FFmpeg-soc] [soc]: r5419 - als/alsdec.c

[Michael Niedermayer]

On Thu, Oct 22, 2009 at 11:29:55AM +0200, Thilo Borgmann wrote:
> Thilo Borgmann schrieb:
> > Michael Niedermayer schrieb:
> >> On Wed, Oct 21, 2009 at 12:33:21PM +0200, Thilo Borgmann wrote:
> >>> Michael Niedermayer schrieb:
> >>>> On Tue, Oct 20, 2009 at 03:00:40PM +0200, thilo.borgmann wrote:
> >>>>> Author: thilo.borgmann
> >>>>> Date: Tue Oct 20 15:00:40 2009
> >>>>> New Revision: 5419
> >>>>>
> >>>>> Log:
> >>>>> Splits reading of block data and decoding of block data.
> >>>>> Introduces ALSBlockData struct.
> >>>> You are missing the "why" part, that should be explained in the commit
> >>>> message
> >>> Yes, sorry.
> >>>
> >>>> also this needs a benchmark as there are many additional dereferences
> >>>> added
> >>> It is a necessary evil to support MCC. If it would be faster the "old"
> >>> way for non-MCC files, would this reason to have both, a split read &
> >>> decode function pair and an all-in-one function?
> >> I think a benchmark is usefull to judge if we should spend time thinking
> >> about alternatives to the many dereferences or not
[...]
> > This is a 30% difference which makes me think to try these alternatives.
> > 
> > What comes into my mind would be to use local copies, thus dereferencing
> > the field of *bd just twice. One at the top and one at the bottom of the
> > function.
> > 
> 
> I tested using local copies instead of dereferencing:
[...]
> That's a 4% gain so I think local copies don't pay off...
> 
> Other alternatives?

i would first confirm that gcc did not do something stupid about inlining.
Or more precissely not inlining some random unrelated function after the
file got bigger ...

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The bravest are surely those who have the clearest vision
of what is before them, glory and danger alike, and yet
notwithstanding go out to meet it. -- Thucydides
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