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.) -- Janne Blomqvist
