On Wed, 14 Mar 2012, Jeff Law wrote: > On 03/14/2012 08:30 AM, Vincent Lefevre wrote: > > > > > (b) Where functions do make attempts at being correctly rounded > > > (especially the IBM Accurate Mathematical Library functions), they tend to > > > be sufficiently slow that the slowness attracts bug reports. Again, this > > > would likely be addressed by new implementations that use careful error > > > bounds and information about worst cases to reduce the cost of being > > > correctly rounding. > > > > I'm not sure that the complaints are about worst cases. More probably > > software implementation vs hardware implementation in the average > > case. But a new software implementation (better in average) could > > help. > The complaints I typically see are about worst case performance. I > occasionally see requests for better performance with the potential loss of > accuracy.
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. -- Joseph S. Myers jos...@codesourcery.com
