On Wed, Aug 13, 2014 at 10:46:45AM +0200, James Darnley wrote:
> On 2014-08-13 04:50, Michael Niedermayer wrote:
> > On Tue, Aug 12, 2014 at 11:22:07PM +0200, James Darnley wrote:
> >> ---
> >> libavcodec/flacdsp.h | 7 +++++++
> >> 1 files changed, 7 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/libavcodec/flacdsp.h b/libavcodec/flacdsp.h
> >> index 272cf2a..36cd904 100644
> >> --- a/libavcodec/flacdsp.h
> >> +++ b/libavcodec/flacdsp.h
> >> @@ -27,6 +27,13 @@ typedef struct FLACDSPContext {
> >> int len, int shift);
> >> void (*lpc)(int32_t *samples, const int coeffs[32], int order,
> >> int qlevel, int len);
> >> + /**
> >> + * This function has some limitations with various configurations:
> >> + * - when CONFIG_SMALL is 0 there is an unrolled loop which assumes
> >> the
> >> + * maximum value of order is 32.
> >> + * - when SSE4 (or newer) is available on x86 there is an unrolled
> >> copy
> >> + * which also assumes the maximum value of order is 0.
> >> + */
> >
> > sounds like
> >
> > printf()
> > on fridays with SSE4 this is limited to 27 characters
> >
> > a function either should have a limit or not have one, it should
> > not depend on other factors
> >
> > People using this function must be able to tell in what cases they
> > can use it
> >
> > and People optimizing the function need to know which cases their
> > optimized code must support
> >
> > the API defines both
>
> I don't get it. FLAC only allows upto 32-order LPC. This was,
> apprarently, an acceptable assumption to make for the unrolled C code
> yet somehow I can't make the same assumption for assembly.theres some kind of misunderatanding here its perfectly fine to say /** * This function supports upto a order of 32 */ what i think is a really bad idea is to make the API conditional on cpu features and build flags. What if someone wants to add a SSE2 optimization that works just up to order 32 ? he cannot do it without changing the API and checking that all uses of the API are safe with the new limitation > > >> + * which also assumes the maximum value of order is 0. > ^^^ > Is it this bit that is confusing? Because I only now see that typo. Of > course that should say "32". that too [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are best at talking, realize last or never when they are wrong.
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