diff options
Diffstat (limited to 'lib/msun/src/k_log.h')
| -rw-r--r-- | lib/msun/src/k_log.h | 38 |
1 files changed, 11 insertions, 27 deletions
diff --git a/lib/msun/src/k_log.h b/lib/msun/src/k_log.h index 206355c..aaff8bd 100644 --- a/lib/msun/src/k_log.h +++ b/lib/msun/src/k_log.h @@ -14,8 +14,9 @@ #include <sys/cdefs.h> __FBSDID("$FreeBSD$"); -/* __kernel_log(x) - * Return log(x) - (x-1) for x in ~[sqrt(2)/2, sqrt(2)]. +/* + * k_log1p(f): + * Return log(1+f) - f for 1+f in ~[sqrt(2)/2, sqrt(2)]. * * The following describes the overall strategy for computing * logarithms in base e. The argument reduction and adding the final @@ -80,37 +81,20 @@ Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */ Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */ /* - * We always inline __kernel_log(), since doing so produces a + * We always inline k_log1p(), since doing so produces a * substantial performance improvement (~40% on amd64). */ static inline double -__kernel_log(double x) +k_log1p(double f) { - double hfsq,f,s,z,R,w,t1,t2; - int32_t hx,i,j; - u_int32_t lx; - - EXTRACT_WORDS(hx,lx,x); + double hfsq,s,z,R,w,t1,t2; - f = x-1.0; - if((0x000fffff&(2+hx))<3) { /* -2**-20 <= f < 2**-20 */ - if(f==0.0) return 0.0; - return f*f*(0.33333333333333333*f-0.5); - } - s = f/(2.0+f); + s = f/(2.0+f); z = s*s; - hx &= 0x000fffff; - i = hx-0x6147a; w = z*z; - j = 0x6b851-hx; - t1= w*(Lg2+w*(Lg4+w*Lg6)); - t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7))); - i |= j; + t1= w*(Lg2+w*(Lg4+w*Lg6)); + t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7))); R = t2+t1; - if (i>0) { - hfsq=0.5*f*f; - return s*(hfsq+R) - hfsq; - } else { - return s*(R-f); - } + hfsq=0.5*f*f; + return s*(hfsq+R); } |
