On Mon, 2014-06-09 at 15:16 -0700, Junio C Hamano wrote: > David Turner <dturner@xxxxxxxxxxxxxxxx> writes: > > > Since Junio has picked up the first patch from previous versions of > > this series, I'm just going to send the second (SSE) one. I decided > > not to s/NO_SSE42/!HAVE_SSE42/ because it looks like git mostly uses > > the former convention (for instance, that's what GIT_PARSE_WITH > > generates). > > Yeah but NO_FROTZ is used only when FROTZ is something everybody is > expected to have (e.g. it's in posix, people ought to have it, but > we do support those who don't), isn't it? For a very arch specific > stuff like sse42, I'd feel better to make it purely opt-in by > forcing people to explicitly say HAVE_SSE42 to enable it. The patch now has two kinds of autodetection: 1. At build-time, we check for the compiler supporting -msse4.2. If it does, and if the user has not explicitly done --without-sse, then we build with SSE support. This does not mean that the SSE code will necessarily be used because: 2. At run-time, if we have built with SSE support, we check cpuid to choose a version of the function that will run on the current CPU. So I think we never hit a case where we try to use SSE and fail, which is the major reason I see to make it non-default. To me, this means that we should not require people to explicitly request SSE, because we generally want to try to provide the most-efficient version of git that will work everywhere. In fact, I am not sure we need a --without-sse option at all, since all it saves is a cpuid instruction. But I don't need to remove the option, in case there's a use for it I'm not thinking of. -- 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