1239310Sdim 2239310Sdim/* @(#)e_acos.c 1.3 95/01/18 */ 3239310Sdim/* FreeBSD: head/lib/msun/src/e_acos.c 176451 2008-02-22 02:30:36Z das */ 4239310Sdim/* 5239310Sdim * ==================================================== 6239310Sdim * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 7239310Sdim * 8239310Sdim * Developed at SunSoft, a Sun Microsystems, Inc. business. 9239310Sdim * Permission to use, copy, modify, and distribute this 10239310Sdim * software is freely granted, provided that this notice 11239310Sdim * is preserved. 12239310Sdim * ==================================================== 13239310Sdim */ 14239310Sdim 15249423Sdim#include <sys/cdefs.h> 16249423Sdim__FBSDID("$FreeBSD: releng/11.0/lib/msun/src/e_acosl.c 181152 2008-08-02 03:56:22Z das $"); 17249423Sdim 18239310Sdim/* 19239310Sdim * See comments in e_acos.c. 20249423Sdim * Converted to long double by David Schultz <das@FreeBSD.ORG>. 21239310Sdim */ 22239310Sdim 23239310Sdim#include <float.h> 24239310Sdim 25239310Sdim#include "invtrig.h" 26239310Sdim#include "math.h" 27239310Sdim#include "math_private.h" 28249423Sdim 29249423Sdimstatic const long double 30249423Sdimone= 1.00000000000000000000e+00; 31249423Sdim 32239310Sdim#ifdef __i386__ 33239310Sdim/* XXX Work around the fact that gcc truncates long double constants on i386 */ 34249423Sdimstatic volatile double 35239310Sdimpi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */ 36249423Sdimpi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */ 37249423Sdim#define pi ((long double)pi1 + pi2) 38239310Sdim#else 39249423Sdimstatic const long double 40249423Sdimpi = 3.14159265358979323846264338327950280e+00L; 41249423Sdim#endif 42249423Sdim 43249423Sdimlong double 44239310Sdimacosl(long double x) 45251662Sdim{ 46251662Sdim union IEEEl2bits u; 47251662Sdim long double z,p,q,r,w,s,c,df; 48251662Sdim int16_t expsign, expt; 49251662Sdim u.e = x; 50239310Sdim expsign = u.xbits.expsign; 51239310Sdim expt = expsign & 0x7fff; 52239310Sdim if(expt >= BIAS) { /* |x| >= 1 */ 53239310Sdim if(expt==BIAS && ((u.bits.manh&~LDBL_NBIT)|u.bits.manl)==0) { 54239310Sdim if (expsign>0) return 0.0; /* acos(1) = 0 */ 55239310Sdim else return pi+2.0*pio2_lo; /* acos(-1)= pi */ 56239310Sdim } 57239310Sdim return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 58239310Sdim } 59249423Sdim if(expt<BIAS-1) { /* |x| < 0.5 */ 60249423Sdim if(expt<ACOS_CONST) return pio2_hi+pio2_lo;/*x tiny: acosl=pi/2*/ 61239310Sdim z = x*x; 62239310Sdim p = P(z); 63239310Sdim q = Q(z); 64239310Sdim r = p/q; 65239310Sdim return pio2_hi - (x - (pio2_lo-x*r)); 66239310Sdim } else if (expsign<0) { /* x < -0.5 */ 67249423Sdim z = (one+x)*0.5; 68249423Sdim p = P(z); 69249423Sdim q = Q(z); 70249423Sdim s = sqrtl(z); 71249423Sdim r = p/q; 72249423Sdim w = r*s-pio2_lo; 73239310Sdim return pi - 2.0*(s+w); 74239310Sdim } else { /* x > 0.5 */ 75239310Sdim z = (one-x)*0.5; 76239310Sdim s = sqrtl(z); 77239310Sdim u.e = s; 78239310Sdim u.bits.manl = 0; 79239310Sdim df = u.e; 80239310Sdim c = (z-df*df)/(s+df); 81239310Sdim p = P(z); 82251662Sdim q = Q(z); 83251662Sdim r = p/q; 84239310Sdim w = r*s+c; 85239310Sdim return 2.0*(df+w); 86239310Sdim } 87239310Sdim} 88239310Sdim