1174698Sdas/* 2174698Sdas * From: @(#)s_ilogb.c 5.1 93/09/24 3174698Sdas * ==================================================== 4174698Sdas * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5174698Sdas * 6174698Sdas * Developed at SunPro, a Sun Microsystems, Inc. business. 7174698Sdas * Permission to use, copy, modify, and distribute this 8174698Sdas * software is freely granted, provided that this notice 9174698Sdas * is preserved. 10174698Sdas * ==================================================== 11174698Sdas */ 12174698Sdas 13324006Sdim#include <sys/cdefs.h> 14324006Sdim__FBSDID("$FreeBSD: stable/11/lib/msun/src/s_logbl.c 324006 2017-09-26 09:01:56Z dim $"); 15174698Sdas 16174698Sdas#include <float.h> 17174698Sdas#include <limits.h> 18174698Sdas#include <math.h> 19174698Sdas 20174698Sdas#include "fpmath.h" 21174698Sdas 22174698Sdaslong double 23174698Sdaslogbl(long double x) 24174698Sdas{ 25174698Sdas union IEEEl2bits u; 26174698Sdas unsigned long m; 27174698Sdas int b; 28174698Sdas 29174698Sdas u.e = x; 30174698Sdas if (u.bits.exp == 0) { 31174698Sdas if ((u.bits.manl | u.bits.manh) == 0) { /* x == 0 */ 32174698Sdas u.bits.sign = 1; 33174698Sdas return (1.0L / u.e); 34174698Sdas } 35174698Sdas /* denormalized */ 36174698Sdas if (u.bits.manh == 0) { 37174698Sdas m = 1lu << (LDBL_MANL_SIZE - 1); 38174698Sdas for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1) 39174698Sdas b++; 40174698Sdas } else { 41174698Sdas m = 1lu << (LDBL_MANH_SIZE - 1); 42174698Sdas for (b = 0; !(u.bits.manh & m); m >>= 1) 43174698Sdas b++; 44174698Sdas } 45174698Sdas#ifdef LDBL_IMPLICIT_NBIT 46174698Sdas b++; 47174698Sdas#endif 48174698Sdas return ((long double)(LDBL_MIN_EXP - b - 1)); 49174698Sdas } 50174698Sdas if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) /* normal */ 51174698Sdas return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1)); 52174698Sdas else /* +/- inf or nan */ 53174698Sdas return (x * x); 54174698Sdas} 55