2 /* @(#)e_acos.c 1.3 95/01/18 */
3 /* FreeBSD: head/lib/msun/src/e_acos.c 176451 2008-02-22 02:30:36Z das */
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 * Developed at SunSoft, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
12 * ====================================================
16 * See comments in e_acos.c.
17 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
24 #include "math_private.h"
26 static const long double
27 one= 1.00000000000000000000e+00;
30 /* XXX Work around the fact that gcc truncates long double constants on i386 */
31 static volatile double
32 pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */
33 pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */
34 #define pi ((long double)pi1 + pi2)
36 static const long double
37 pi = 3.14159265358979323846264338327950280e+00L;
44 long double z,p,q,r,w,s,c,df;
45 int16_t expsign, expt;
47 expsign = u.xbits.expsign;
48 expt = expsign & 0x7fff;
49 if(expt >= BIAS) { /* |x| >= 1 */
50 if(expt==BIAS && ((u.bits.manh&~LDBL_NBIT)|u.bits.manl)==0) {
51 if (expsign>0) return 0.0; /* acos(1) = 0 */
52 else return pi+2.0*pio2_lo; /* acos(-1)= pi */
54 return (x-x)/(x-x); /* acos(|x|>1) is NaN */
56 if(expt<BIAS-1) { /* |x| < 0.5 */
57 if(expt<ACOS_CONST) return pio2_hi+pio2_lo;/*x tiny: acosl=pi/2*/
62 return pio2_hi - (x - (pio2_lo-x*r));
63 } else if (expsign<0) { /* x < -0.5 */
70 return pi - 2.0*(s+w);
71 } else { /* x > 0.5 */