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Diffstat (limited to 'lib/msun/src/s_logb.c')
-rw-r--r-- | lib/msun/src/s_logb.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/lib/msun/src/s_logb.c b/lib/msun/src/s_logb.c new file mode 100644 index 0000000..a47e354 --- /dev/null +++ b/lib/msun/src/s_logb.c @@ -0,0 +1,49 @@ +/* @(#)s_logb.c 5.1 93/09/24 */ +/* + * ==================================================== + * 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("$FreeBSD$"); + +/* + * double logb(x) + * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. + * Use ilogb instead. + */ + +#include <float.h> + +#include "math.h" +#include "math_private.h" + +static const double +two54 = 1.80143985094819840000e+16; /* 43500000 00000000 */ + +double +logb(double x) +{ + int32_t lx,ix; + EXTRACT_WORDS(ix,lx,x); + ix &= 0x7fffffff; /* high |x| */ + if((ix|lx)==0) return -1.0/fabs(x); + if(ix>=0x7ff00000) return x*x; + if(ix<0x00100000) { + x *= two54; /* convert subnormal x to normal */ + GET_HIGH_WORD(ix,x); + ix &= 0x7fffffff; + return (double) ((ix>>20)-1023-54); + } else + return (double) ((ix>>20)-1023); +} + +#if (LDBL_MANT_DIG == 53) +__weak_reference(logb, logbl); +#endif |