On Sat, 28 May 2005, Scott Robert Ladd wrote: > Toon Moene wrote: > > Good Luck :-) > > > > http://gcc.gnu.org/ml/gcc/2001-08/msg00368.html > > > > (it's only four years ago - I can also show you my contributions in this > > thread in 1999, i.e., the previous millennium). > > Just out of curiosity, why did previous efforts fail in this regard? Was > it simply too much effort to identify all the transformations? Did the > GCC community fail to come to a consensus? Or was it simply -- as I'm > coming to suspect -- that the work involved is not justified by the result?
They didn't fail altogether; -ffast-math was split into multiple options (-funsafe-math-optimizations -fno-trapping-math etc.) in March 2001, following an analysis of everything that checked flag_fast_math <http://gcc.gnu.org/ml/gcc-patches/2000-12/msg00690.html>. Unfortunately this never got followed up properly by defining separate preprocessor macros for each option, so if you use the individual options then glibc headers checking __FAST_MATH__ may not enable optimizations which would in fact be safe with the subset of options specified. And as the current discussion illustrates, -funsafe-math-optimizations itself has become a catch-all for many different optimizations, such as -ffast-math was. -- Joseph S. Myers http://www.srcf.ucam.org/~jsm28/gcc/ [EMAIL PROTECTED] (personal mail) [EMAIL PROTECTED] (CodeSourcery mail) [EMAIL PROTECTED] (Bugzilla assignments and CCs)
