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Diffstat (limited to 'lib/msun/src/e_log2f.c')
-rw-r--r-- | lib/msun/src/e_log2f.c | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/lib/msun/src/e_log2f.c b/lib/msun/src/e_log2f.c new file mode 100644 index 0000000..bb308d3 --- /dev/null +++ b/lib/msun/src/e_log2f.c @@ -0,0 +1,58 @@ +/* + * ==================================================== + * 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. + * ==================================================== + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +/* + * Return the base 2 logarithm of x. See k_log.c for details on the algorithm. + */ + +#include "math.h" +#include "math_private.h" +#include "k_logf.h" + +static const float +two25 = 3.3554432000e+07, /* 0x4c000000 */ +ivln2hi = 1.4428710938e+00, /* 0x3fb8b000 */ +ivln2lo = -1.7605285393e-04; /* 0xb9389ad4 */ + +static const float zero = 0.0; + +float +__ieee754_log2f(float x) +{ + float f,hi,lo; + int32_t i,k,hx; + + GET_FLOAT_WORD(hx,x); + + k=0; + if (hx < 0x00800000) { /* x < 2**-126 */ + if ((hx&0x7fffffff)==0) + return -two25/zero; /* log(+-0)=-inf */ + if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ + k -= 25; x *= two25; /* subnormal number, scale up x */ + GET_FLOAT_WORD(hx,x); + } + if (hx >= 0x7f800000) return x+x; + k += (hx>>23)-127; + hx &= 0x007fffff; + i = (hx+(0x4afb0d))&0x800000; + SET_FLOAT_WORD(x,hx|(i^0x3f800000)); /* normalize x or x/2 */ + k += (i>>23); + f = __kernel_logf(x); + x = x - (float)1.0; + GET_FLOAT_WORD(hx,x); + SET_FLOAT_WORD(hi,hx&0xfffff000); + lo = x - hi; + return (x+f)*ivln2lo + (lo+f)*ivln2hi + hi*ivln2hi + k; +} |