On 2018-09-05 14:08:11 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > On 2018-09-05 10:05:26 -0400, Tom Lane wrote: > >> One thought is that maybe we should provide a way to override this, > >> in case somebody really can't or doesn't want to use -msse2, and > >> is willing to put up with platform-dependent float behavior. > > > IDK, people that are capable of making that decision can just hack > > configure. > > "Just hacking configure" is a pretty high bar for most folk.
Sure. But being able to accurately judge whether you're ok that math behaviour doesn't work as documented seems like a high bar too. And this'd only be relevant if they insist on using clang rather than gcc. > If you wanted to argue that the set of people who still want to run PG > on pre-SSE2 hardware is the empty set, that'd be an easier sell > really. I think it's an empty set, yea, especially with clang. > But what I'm really concerned about here, given that we're apparently > talking about an ABI change, is that someone might want to run on a > platform where the libraries insist on the x87 way. > I'm actually a bit surprised to hear that you can just randomly add > -msse2 on BSDen. Do they ship separate copies of libc et al to make > that work? I don't think we're talking about an ABI change - with -msse2 the calling conventions are unchanged, the stuff just gets moved out of the x87 registers into SSE ones / xmm for the actual math. Which in turn solves our "80bit register" problem. There really shouldn't be any need for libc6 itself to care. Greetings, Andres Freund