Diego Biurrun <[email protected]> writes: > On Sat, May 12, 2012 at 08:59:00AM +0200, Vitor Sessak wrote: >> --- >> libavcodec/x86/fft.c | 45 +++++++++++++++++++++++---------------------- >> 1 files changed, 23 insertions(+), 22 deletions(-) > > funcTIons > > This may be a naive question because I'm far from deeply familiar with > the x86 code, but I don't understand why you make change you propose > in this patch.
Probably because I asked for it. Using if/else if chains, some assignments have to be duplicated. In this particular case, the avx part assigns sse versions of the imdct_calc and fft_permute functions since those do not have sse2 or avx versions. Now suppose someone adds sse2 optimisations for all the functions. With the current style, this would require updating the assignments in the avx section in order for such machines to get the best implementation. With the patch, higher-ranked extensions simply inherit whatever they do not set explicitly from the next lower version, and things added at the sse2 level would be automatically used by avx without the need to update anything. This is how we do function selection in most other places. -- Måns Rullgård [email protected] _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
