On Sun, Jun 1, 2014 at 11:09 PM, Janne Blomqvist <blomqvist.ja...@gmail.com> wrote: > On Sun, Jun 1, 2014 at 9:52 AM, Mike Izbicki <mike.izbi...@gmail.com> wrote: >> I'm trying to copy gcc's behavior with the -ffast-math compiler flag >> into haskell's ghc compiler. The only documentation I can find about >> it is at: >> >> https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html >> >> I understand how floating point operations work and have come up with >> a reasonable list of optimizations to perform. But I doubt it is >> exhaustive. >> >> My question is: where can I find all the gory details about what gcc >> will do with this flag? I'm perfectly willing to look at source code >> if that's what it takes. > > In addition to the official documentation, a nice overview is at > > https://gcc.gnu.org/wiki/FloatingPointMath > > Though for the gory details and authoritative answers I suppose you'd > have to look into the source code. > >> Also, are there any optimizations that you wish -ffast-math could >> perform, but for various architectural reasons they don't fit into >> gcc? > > There are of course a (nearly endless?) list of optimizations that > could be done but aren't (lack of manpower, impractical, whatnot). I'm > not sure there are any interesting optimizations that would be > dependent on loosening -ffast-math further? > > (One thing I wish wouldn't be included in -ffast-math is > -fcx-limited-range; the naive complex division algorithm can easily > lead to comically poor results.)
Which is kinda interesting because the Google folks have been trying to turn on -fcx-limited-range for C++ a few times now. Thanks, Andrew Pinski > > -- > Janne Blomqvist
