[avr-libc-dev] tanh in libm

[René Liebscher]

Hi,

I have question about the tanh function in libm.

As I can see in
http://savannah.nongnu.org/cgi-bin/viewcvs/avr-libc/avr-libc/libm/fplib/tanh.S?rev=1.2&content-type=text/vnd.viewcvs-markup
there are two ways to calculate the result.

The questions is why was sinh/cosh choosen. (The other way is commented 
out.)
Comparing which functions are called to calculate tanh I find sinh/cosh 
needs one call to exp, two calls to inverse and one call to ldexp more 
than the other way. So I think the current solution is slower than the 
other.
(And it takes more memory if you don't use sinh or cosh in your program.)

If the other solution brings also correct results and is faster, is 
there a simple way to integrate it in my program without to recompile 
the math library.

Kind regards
Rene Liebscher