diff options
Diffstat (limited to 'sysdeps/ieee754/dbl-64/e_log2.c')
| -rw-r--r-- | sysdeps/ieee754/dbl-64/e_log2.c | 34 |
1 files changed, 12 insertions, 22 deletions
diff --git a/sysdeps/ieee754/dbl-64/e_log2.c b/sysdeps/ieee754/dbl-64/e_log2.c index f05d0ce966..be41cb4e68 100644 --- a/sysdeps/ieee754/dbl-64/e_log2.c +++ b/sysdeps/ieee754/dbl-64/e_log2.c @@ -21,14 +21,14 @@ * 2. Approximation of log(1+f). * Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s) * = 2s + 2/3 s**3 + 2/5 s**5 + ....., - * = 2s + s*R + * = 2s + s*R * We use a special Reme algorithm on [0,0.1716] to generate - * a polynomial of degree 14 to approximate R The maximum error + * a polynomial of degree 14 to approximate R The maximum error * of this polynomial approximation is bounded by 2**-58.45. In * other words, - * 2 4 6 8 10 12 14 + * 2 4 6 8 10 12 14 * R(z) ~ Lg1*s +Lg2*s +Lg3*s +Lg4*s +Lg5*s +Lg6*s +Lg7*s - * (the values of Lg1 to Lg7 are listed in the program) + * (the values of Lg1 to Lg7 are listed in the program) * and * | 2 14 | -58.45 * | Lg1*s +...+Lg7*s - R(z) | <= 2 @@ -57,11 +57,7 @@ #include "math.h" #include "math_private.h" -#ifdef __STDC__ static const double -#else -static double -#endif ln2 = 0.69314718055994530942, two54 = 1.80143985094819840000e+16, /* 43500000 00000000 */ Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */ @@ -72,18 +68,10 @@ Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */ Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */ Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */ -#ifdef __STDC__ static const double zero = 0.0; -#else -static double zero = 0.0; -#endif -#ifdef __STDC__ - double __ieee754_log2(double x) -#else - double __ieee754_log2(x) - double x; -#endif +double +__ieee754_log2(double x) { double hfsq,f,s,z,R,w,t1,t2,dk; int32_t k,hx,i,j; @@ -93,13 +81,14 @@ static double zero = 0.0; k=0; if (hx < 0x00100000) { /* x < 2**-1022 */ - if (((hx&0x7fffffff)|lx)==0) + if (__builtin_expect(((hx&0x7fffffff)|lx)==0, 0)) return -two54/(x-x); /* log(+-0)=-inf */ - if (hx<0) return (x-x)/(x-x); /* log(-#) = NaN */ + if (__builtin_expect(hx<0, 0)) + return (x-x)/(x-x); /* log(-#) = NaN */ k -= 54; x *= two54; /* subnormal number, scale up x */ GET_HIGH_WORD(hx,x); } - if (hx >= 0x7ff00000) return x+x; + if (__builtin_expect(hx >= 0x7ff00000, 0)) return x+x; k += (hx>>20)-1023; hx &= 0x000fffff; i = (hx+0x95f64)&0x100000; @@ -112,7 +101,7 @@ static double zero = 0.0; R = f*f*(0.5-0.33333333333333333*f); return dk-(R-f)/ln2; } - s = f/(2.0+f); + s = f/(2.0+f); z = s*s; i = hx-0x6147a; w = z*z; @@ -128,3 +117,4 @@ static double zero = 0.0; return dk-((s*(f-R))-f)/ln2; } } +strong_alias (__ieee754_log2, __log2_finite) |