Index: uClibc/test/math/libm-test.inc =================================================================== --- uClibc.orig/test/math/libm-test.inc 2008-07-25 11:03:24.000000000 +0200 +++ uClibc/test/math/libm-test.inc 2008-08-28 10:54:29.714525665 +0200 @@ -3414,7 +3414,6 @@ } -#if 0 static void log2_test (void) { @@ -3444,7 +3443,6 @@ END (log2); } -#endif static void @@ -4967,9 +4965,7 @@ log_test (); log10_test (); log1p_test (); -#if 0 log2_test (); -#endif logb_test (); modf_test (); ilogb_test (); Index: uClibc/libm/Makefile.in =================================================================== --- uClibc.orig/libm/Makefile.in 2008-07-25 11:03:27.000000000 +0200 +++ uClibc/libm/Makefile.in 2008-08-28 10:54:29.714525665 +0200 @@ -62,7 +62,7 @@ libm_CSRC := \ e_acos.c e_acosh.c e_asin.c e_atan2.c e_atanh.c e_cosh.c \ e_exp.c e_fmod.c e_gamma.c e_gamma_r.c e_hypot.c e_j0.c \ - e_j1.c e_jn.c e_lgamma.c e_lgamma_r.c e_log.c e_log10.c \ + e_j1.c e_jn.c e_lgamma.c e_lgamma_r.c e_log.c e_log2.c e_log10.c \ e_pow.c e_remainder.c e_rem_pio2.c e_scalb.c e_sinh.c \ e_sqrt.c k_cos.c k_rem_pio2.c k_sin.c k_standard.c k_tan.c \ s_asinh.c s_atan.c s_cbrt.c s_ceil.c s_copysign.c s_cos.c \ @@ -73,7 +73,7 @@ s_tanh.c s_trunc.c w_acos.c w_acosh.c w_asin.c w_atan2.c w_atanh.c \ w_cabs.c w_cosh.c w_drem.c w_exp.c w_fmod.c w_gamma.c w_gamma_r.c \ w_hypot.c w_j0.c w_j1.c w_jn.c w_lgamma.c w_lgamma_r.c \ - w_log.c w_log10.c w_pow.c w_remainder.c w_scalb.c w_sinh.c \ + w_log.c w_log2.c w_log10.c w_pow.c w_remainder.c w_scalb.c w_sinh.c \ w_sqrt.c fpmacros.c nan.c carg.c s_llrint.c FL_MOBJ := \ acosf.o acoshf.o asinf.o asinhf.o atan2f.o atanf.o atanhf.o cbrtf.o \ @@ -89,10 +89,10 @@ libm_CSRC := \ w_acos.c w_asin.c s_atan.c w_atan2.c s_ceil.c s_cos.c \ w_cosh.c w_exp.c s_fabs.c s_floor.c w_fmod.c s_frexp.c \ - s_ldexp.c w_log.c w_log10.c s_modf.c w_pow.c s_sin.c \ + s_ldexp.c w_log.c w_log2.c w_log10.c s_modf.c w_pow.c s_sin.c \ w_sinh.c w_sqrt.c s_tan.c s_tanh.c \ s_expm1.c s_scalbn.c s_copysign.c e_acos.c e_asin.c e_atan2.c \ - k_cos.c e_cosh.c e_exp.c e_fmod.c e_log.c e_log10.c e_pow.c \ + k_cos.c e_cosh.c e_exp.c e_fmod.c e_log.c e_log2.c e_log10.c e_pow.c \ k_sin.c e_sinh.c e_sqrt.c k_tan.c e_rem_pio2.c k_rem_pio2.c \ s_finite.c # We'll add sqrtf to avoid problems with libstdc++ Index: uClibc/libm/w_log2.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ uClibc/libm/w_log2.c 2008-08-28 10:58:48.676013259 +0200 @@ -0,0 +1,33 @@ +/* + * wrapper log2(X) + */ + +#include "math.h" +#include "math_private.h" + +libm_hidden_proto(log2) +#ifdef __STDC__ + double log2(double x) /* wrapper log */ +#else + double log2(x) /* wrapper log */ + double x; +#endif +{ +#ifdef _IEEE_LIBM + return __ieee754_log2 (x); +#else + double z; + z = __ieee754_log2 (x); + if (_LIB_VERSION == _IEEE_ || __isnan (x)) return z; + if (x <= 0.0) + { + if (x == 0.0) + return __kernel_standard (x, x, 48); /* log2 (0) */ + else + return __kernel_standard (x, x, 49); /* log2 (x < 0) */ + } + else + return z; +#endif +} +libm_hidden_def(log2) Index: uClibc/libm/e_log2.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ uClibc/libm/e_log2.c 2008-08-28 10:54:29.717859030 +0200 @@ -0,0 +1,130 @@ +/* Adapted for log2 by Ulrich Drepper . */ +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunPro, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* __ieee754_log2(x) + * Return the logarithm to base 2 of x + * + * Method : + * 1. Argument Reduction: find k and f such that + * x = 2^k * (1+f), + * where sqrt(2)/2 < 1+f < sqrt(2) . + * + * 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 + * We use a special Reme algorithm on [0,0.1716] to generate + * 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 + * 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) + * and + * | 2 14 | -58.45 + * | Lg1*s +...+Lg7*s - R(z) | <= 2 + * | | + * Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2. + * In order to guarantee error in log below 1ulp, we compute log + * by + * log(1+f) = f - s*(f - R) (if f is not too large) + * log(1+f) = f - (hfsq - s*(hfsq+R)). (better accuracy) + * + * 3. Finally, log(x) = k + log(1+f). + * = k+(f-(hfsq-(s*(hfsq+R)))) + * + * Special cases: + * log2(x) is NaN with signal if x < 0 (including -INF) ; + * log2(+INF) is +INF; log(0) is -INF with signal; + * log2(NaN) is that NaN with no signal. + * + * Constants: + * The hexadecimal values are the intended ones for the following + * constants. The decimal values may be used, provided that the + * compiler will convert from decimal to binary accurately enough + * to produce the hexadecimal values shown. + */ + +#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 */ +Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */ +Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */ +Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */ +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 attribute_hidden __ieee754_log2(double x) +#else + double attribute_hidden __ieee754_log2(x) + double x; +#endif +{ + double hfsq,f,s,z,R,w,t1,t2,dk; + int32_t k,hx,i,j; + u_int32_t lx; + + EXTRACT_WORDS(hx,lx,x); + + k=0; + if (hx < 0x00100000) { /* x < 2**-1022 */ + if (((hx&0x7fffffff)|lx)==0) + return -two54/(x-x); /* log(+-0)=-inf */ + if (hx<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; + k += (hx>>20)-1023; + hx &= 0x000fffff; + i = (hx+0x95f64)&0x100000; + SET_HIGH_WORD(x,hx|(i^0x3ff00000)); /* normalize x or x/2 */ + k += (i>>20); + dk = (double) k; + f = x-1.0; + if((0x000fffff&(2+hx))<3) { /* |f| < 2**-20 */ + if(f==zero) return dk; + R = f*f*(0.5-0.33333333333333333*f); + return dk-(R-f)/ln2; + } + s = f/(2.0+f); + z = s*s; + 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; + R = t2+t1; + if(i>0) { + hfsq=0.5*f*f; + return dk-((hfsq-(s*(hfsq+R)))-f)/ln2; + } else { + return dk-((s*(f-R))-f)/ln2; + } +} Index: uClibc/libm/math_private.h =================================================================== --- uClibc.orig/libm/math_private.h 2008-05-07 00:23:27.000000000 +0200 +++ uClibc/libm/math_private.h 2008-08-28 10:54:29.717859030 +0200 @@ -158,6 +158,7 @@ extern double __ieee754_acos (double) attribute_hidden; extern double __ieee754_acosh (double) attribute_hidden; extern double __ieee754_log (double) attribute_hidden; +extern double __ieee754_log2 (double) attribute_hidden; extern double __ieee754_atanh (double) attribute_hidden; extern double __ieee754_asin (double) attribute_hidden; extern double __ieee754_atan2 (double,double) attribute_hidden; Index: uClibc/libm/float_wrappers.c =================================================================== --- uClibc.orig/libm/float_wrappers.c 2008-05-07 00:23:27.000000000 +0200 +++ uClibc/libm/float_wrappers.c 2008-08-28 10:54:29.717859030 +0200 @@ -20,7 +20,6 @@ #undef L_fmaf /*float fmaf(float, float, float);*/ #undef L_fmaxf /*float fmaxf(float, float);*/ #undef L_fminf /*float fminf(float, float);*/ -#undef L_log2f /*float log2f(float);*/ #undef L_nearbyintf /*float nearbyintf(float);*/ #undef L_nexttowardf /*float nexttowardf(float, long double);*/ #undef L_remquof /*float remquof(float, float, int *);*/ @@ -55,6 +54,7 @@ float lgammaf(float); long long llroundf(float); float log10f(float); +float log2f(float); float log1pf(float); float logbf(float); float logf(float);