1 /* $NetBSD: e_acosl.c,v 1.5 2024/06/09 13:35:38 riastradh Exp $ */ 2 3 /* FreeBSD: head/lib/msun/src/e_acos.c 176451 2008-02-22 02:30:36Z das */ 4 /* 5 * ==================================================== 6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 7 * 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 11 * is preserved. 12 * ==================================================== 13 */ 14 15 #include <sys/cdefs.h> 16 __RCSID("$NetBSD: e_acosl.c,v 1.5 2024/06/09 13:35:38 riastradh Exp $"); 17 18 /* 19 * See comments in e_acos.c. 20 * Converted to long double by David Schultz <das@FreeBSD.ORG>. 21 */ 22 23 #include "namespace.h" 24 25 #include <float.h> 26 #include <machine/ieee.h> 27 28 #include "math.h" 29 #include "math_private.h" 30 31 #ifdef __HAVE_LONG_DOUBLE 32 33 __weak_alias(acosl, _acosl) 34 35 #if LDBL_MANT_DIG == 64 36 #include "../ld80/invtrig.h" 37 #elif LDBL_MANT_DIG == 113 38 #include "../ld128/invtrig.h" 39 #else 40 #error "Unsupported long double format" 41 #endif 42 43 #ifdef LDBL_IMPLICIT_NBIT 44 #define LDBL_NBIT 0 45 #endif 46 47 static const long double 48 one= 1.00000000000000000000e+00; 49 50 #ifdef __i386__ 51 /* XXX Work around the fact that gcc truncates long double constants on i386 */ 52 static volatile double 53 pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */ 54 pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */ 55 #define pi ((long double)pi1 + pi2) 56 #else 57 static const long double 58 pi = 3.14159265358979323846264338327950280e+00L; 59 #endif 60 61 long double 62 acosl(long double x) 63 { 64 union ieee_ext_u u; 65 long double z,p,q,r,w,s,c,df; 66 int16_t expsign, expt; 67 u.extu_ld = x; 68 expsign = GET_EXPSIGN(&u); 69 expt = expsign & 0x7fff; 70 if(expt >= BIAS) { /* |x| >= 1 */ 71 if(expt==BIAS && ((u.extu_frach&~LDBL_NBIT)|u.extu_fracl)==0) { 72 if (expsign>0) return 0.0; /* acos(1) = 0 */ 73 else return pi+2.0*pio2_lo; /* acos(-1)= pi */ 74 } 75 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 76 } 77 if(expt<BIAS-1) { /* |x| < 0.5 */ 78 if(expt<ACOS_CONST) return pio2_hi+pio2_lo;/*x tiny: acosl=pi/2*/ 79 z = x*x; 80 p = P(z); 81 q = Q(z); 82 r = p/q; 83 return pio2_hi - (x - (pio2_lo-x*r)); 84 } else if (expsign<0) { /* x < -0.5 */ 85 z = (one+x)*0.5; 86 p = P(z); 87 q = Q(z); 88 s = sqrtl(z); 89 r = p/q; 90 w = r*s-pio2_lo; 91 return pi - 2.0*(s+w); 92 } else { /* x > 0.5 */ 93 z = (one-x)*0.5; 94 s = sqrtl(z); 95 u.extu_ld = s; 96 u.extu_fracl = 0; 97 df = u.extu_ld; 98 c = (z-df*df)/(s+df); 99 p = P(z); 100 q = Q(z); 101 r = p/q; 102 w = r*s+c; 103 return 2.0*(df+w); 104 } 105 } 106 #endif 107