On Wed, 14 Mar 2012, Marc Glisse wrote: > On Wed, 14 Mar 2012, Joseph S. Myers wrote: > > > I'd say that "better performance with the potential loss of accuracy" > > should be covered by -ffast-math - that GCC should generate direct use of > > fsin/fcos instructions for sin/cos for -O2 -funsafe-math-optimizations on > > x86_64, as it does on x86, unless there is some reason to think they would > > perform worse than the out-of-line implementation. > > Last time I did some timings (maybe 4 years ago), for double, fsin was slower > than the libm software implementation compiled for x87, which was itself > slower than the same implementation compiled for sse. And the software > implementation was more precise than fsin. My conclusion was to ignore fsin > from then on.
Interesting - hopefully that means the glibc changes Andreas Jaeger and I have been working on to stop using fsin etc. (in the interests of accuracy and fixing the sincos issues discussed lately) won't actually make performance worse. -- Joseph S. Myers jos...@codesourcery.com
