freebsd-src/lib/msun
Bruce Evans 1dd21062e5 Rearranged the polynomial evaluation some more to reduce dependencies.
Instead of echoing the code in a comment, try to describe why we split
up the evaluation in a special way.

The new optimization is mostly to move the evaluation of w = z*z later
so that everything else (except z = x*x) doesn't have to wait for w.
On Athlons, FP multiplication has a latency of 4 cycles so this
optimization saves 4 cycles per call provided no new dependencies are
introduced.  Tweaking the other terms in to reduce dependencies saves
a couple more cycles in some cases (more on AXP than on A64; up to 8
cycles out of 56 altogether in some cases).  The previous version had
a similar optimization for s = z*x.  Special optimizations like these
probably have a larger effect than the simple 2-way vectorization
permitted (but not activated by gcc) in the old version, since 2-way
vectorization is not enough and the polynomial's degree is so small
in the float case that non-vectorizable dependencies dominate.

On an AXP, tanf() on uniformly distributed args in [-2pi, 2pi] now
takes 34-55 cycles (was 39-59 cycles).
2005-11-28 11:46:20 +00:00
..
alpha Replace fegetmask() and fesetmask() with feenableexcept(), 2005-03-16 19:03:46 +00:00
amd64 Add a missing ldexpf() alias for amd64. 2005-09-12 20:54:00 +00:00
arm Replace fegetmask() and fesetmask() with feenableexcept(), 2005-03-16 19:03:46 +00:00
bsdsrc Removed an unused declaration which was so old that it wasn't a prototype 2005-11-18 05:03:12 +00:00
i387 Fixed some comments added in rev.1.5. 2005-10-30 12:21:02 +00:00
ia64 Replace fegetmask() and fesetmask() with feenableexcept(), 2005-03-16 19:03:46 +00:00
man s/5.5/6.0/ in HISTORY section. 2005-11-24 09:25:10 +00:00
powerpc Replace fegetmask() and fesetmask() with feenableexcept(), 2005-03-16 19:03:46 +00:00
sparc64 Replace fegetmask() and fesetmask() with feenableexcept(), 2005-03-16 19:03:46 +00:00
src Rearranged the polynomial evaluation some more to reduce dependencies. 2005-11-28 11:46:20 +00:00
Makefile Detach k_rem_pio2f.c from the build since it is now unused. It is a libm 2005-11-06 17:59:40 +00:00