| |
| /* @(#)e_acos.c 1.3 95/01/18 */ |
| /* FreeBSD: head/lib/msun/src/e_acos.c 176451 2008-02-22 02:30:36Z das */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunSoft, 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("$FreeBSD$"); |
| |
| /* |
| * See comments in e_acos.c. |
| * Converted to long double by David Schultz <das@FreeBSD.ORG>. |
| */ |
| |
| #include <float.h> |
| |
| #include "invtrig.h" |
| #include "math.h" |
| #include "math_private.h" |
| |
| static const long double |
| one= 1.00000000000000000000e+00; |
| |
| #ifdef __i386__ |
| /* XXX Work around the fact that gcc truncates long double constants on i386 */ |
| static volatile double |
| pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */ |
| pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */ |
| #define pi ((long double)pi1 + pi2) |
| #else |
| static const long double |
| pi = 3.14159265358979323846264338327950280e+00L; |
| #endif |
| |
| long double |
| acosl(long double x) |
| { |
| union IEEEl2bits u; |
| long double z,p,q,r,w,s,c,df; |
| int16_t expsign, expt; |
| u.e = x; |
| expsign = u.xbits.expsign; |
| expt = expsign & 0x7fff; |
| if(expt >= BIAS) { /* |x| >= 1 */ |
| if(expt==BIAS && ((u.bits.manh&~LDBL_NBIT)|u.bits.manl)==0) { |
| if (expsign>0) return 0.0; /* acos(1) = 0 */ |
| else return pi+2.0*pio2_lo; /* acos(-1)= pi */ |
| } |
| return (x-x)/(x-x); /* acos(|x|>1) is NaN */ |
| } |
| if(expt<BIAS-1) { /* |x| < 0.5 */ |
| if(expt<ACOS_CONST) return pio2_hi+pio2_lo;/*x tiny: acosl=pi/2*/ |
| z = x*x; |
| p = P(z); |
| q = Q(z); |
| r = p/q; |
| return pio2_hi - (x - (pio2_lo-x*r)); |
| } else if (expsign<0) { /* x < -0.5 */ |
| z = (one+x)*0.5; |
| p = P(z); |
| q = Q(z); |
| s = sqrtl(z); |
| r = p/q; |
| w = r*s-pio2_lo; |
| return pi - 2.0*(s+w); |
| } else { /* x > 0.5 */ |
| z = (one-x)*0.5; |
| s = sqrtl(z); |
| u.e = s; |
| u.bits.manl = 0; |
| df = u.e; |
| c = (z-df*df)/(s+df); |
| p = P(z); |
| q = Q(z); |
| r = p/q; |
| w = r*s+c; |
| return 2.0*(df+w); |
| } |
| } |