The calculation of tanf() which lies in
src/lib/libm/src/k_tanf.c can be modified
according to a bugfix ported on FreeBSD on GitHub:
https://github.com/freebsd/freebsd/commit/152a4c4166c18974fe1fc9d9a8535d78956aca26
And here's the code:
- if(ix<0x31800000) /* x < 2**-28 */
- {if((int)x==0) { /* generate inexact */
- if((ix|(iy+1))==0) return one/fabsf(x);
- else return (iy==1)? x: -one/x;
- }
- }
+ if(ix<0x31800000) { /* x < 2**-28 */
+ if ((int) x == 0) { /* generate inexact */
+ if ((ix | (iy + 1)) == 0)
+ return one / fabsf(x);
+ else {
+ if (iy == 1)
+ return x;
+ else { /* compute -1 / (x+y) carefully */
+ double a, t;
+
+ z = w = x + y;
+ GET_FLOAT_WORD(ix, z);
+ SET_FLOAT_WORD(z, ix & 0xfffff000);
+ v = y - (z - x);
+ t = a = -one / w;
+ GET_FLOAT_WORD(ix, t);
+ SET_FLOAT_WORD(t, ix & 0xfffff000);
+ s = one + t * z;
+ return t + a * (s + t * v);
+ }
+ }
+ }
+ }
Although the bug really only applies to tan() and not tanf(),
there seems to be a precedent that the float versions
of the fdlibm routines should mirror their double counterparts.
Greetings!
