On 14/11/13 21:33, Jeff King wrote: > On Thu, Nov 14, 2013 at 07:19:38PM +0000, Ramsay Jones wrote: > >> Unfortunately, I didn't find time this weekend to finish the msvc build >> fixes. However, after a quick squint at these patches, I think you have >> almost done it for me! :-D >> >> I must have misunderstood the previous discussion, because my patch was >> written on the assumption that the ewah directory wouldn't be "git-ified" >> (e.g. #include git-compat-util.h). > > I think it was up for debate at some point, but we did decide to go > ahead and git-ify. Please feel free to submit further fixups if you need > them. Yep, will do; at present it looks like that one-liner. > >>> - the ewah code used gcc's __builtin_ctzll, but did not provide a >>> suitable fallback. We now provide a fallback in C. >> >> ... here. >> >> I was messing around with several implementations (including the use of >> msvc compiler intrinsics) with the intention of doing some timing tests >> etc. [I suspected my C fallback function (a different implementation to >> yours) would be slightly faster.] > > Yeah, I looked around for several implementations, and ultimately wrote > one that was the most readable to me. The one I found shortest and most > inscrutable was: > > return popcount((x & -x) - 1); > > the details of which I still haven't worked through in my head. ;) Yeah, I stumbled over that one too! > I do think on most platforms that intrinsics or inline assembler are the > way to go. My main goal was to get something correct that would let it > compile everywhere, and then people can use that as a base for > optimizing. Patches welcome. :) Indeed, I can happily leave that to another day (or to someone else more motivated ;-) ATB, Ramsay Jones -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html