On Mon, Jan 18, 2016 at 12:37:58PM +0100, Mats Peterson wrote: > On 01/18/2016 12:35 PM, Michael Niedermayer wrote: > >>> > >>Pure logic tells me it's faster to just increment than involve a > >>series of multiplications. > > > >its not so simple > > > >theres a optimizing compiler between you and the CPU > >the multiplication is a shift really, and the compiler may very well > >change this to dst++, buf++ and buf < buf_end > >or it might use something like p[8*i] and q[i] > >i++ and a i<=0 check, the 8* can on some architectures be free as > >part of addressing memory > > > >if you are interrested in optimizing code see > >http://www.agner.org/optimize/ > > > >and intels Intel 64 and IA-32 Architectures Software Developers Manual > >is invaluable as a reference but not useable for other purposes than > >as a reference (its too huge) > > > > I almost expected that answer, Michael. And I do know there's a lot > going on behind the scenes. But how much is another question. And > don't you think it's cleaner to just increment a variable here? Or > should I revert to the old stuff?
the question is which way its faster, i dont know it. Only testing can tell also either way it should be in a seperate patch [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Avoid a single point of failure, be that a person or equipment.
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