Hi,
I actual found a program that is using log2, so I would be glad
if this function would be integrated. The program is inside qt-embedded-4.4.1
and compiling is failing with this line:
qpf2.cpp:(.text+0x26d8): undefined reference to `log2'
I have attached a patch which should working against latest svn head.
If the patch is okay I will open a bug report too.
--
Bye Henning
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 <[EMAIL PROTECTED]>. */
+/*
+ * ====================================================
+ * 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);
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