2 /* @(#)e_atan2.c 1.3 95/01/18 */
3 /* FreeBSD: head/lib/msun/src/e_atan2.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 #include <sys/cdefs.h>
17 __FBSDID("$FreeBSD$");
20 * See comments in e_atan2.c.
21 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
28 #include "math_private.h"
30 static volatile long double
32 static const long double
36 /* XXX Work around the fact that gcc truncates long double constants on i386 */
37 static volatile double
38 pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */
39 pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */
40 #define pi ((long double)pi1 + pi2)
42 static const long double
43 pi = 3.14159265358979323846264338327950280e+00L;
47 atan2l(long double y, long double x)
49 union IEEEl2bits ux, uy;
52 int16_t exptx, expsignx, expty, expsigny;
55 expsigny = uy.xbits.expsign;
56 expty = expsigny & 0x7fff;
58 expsignx = ux.xbits.expsign;
59 exptx = expsignx & 0x7fff;
61 if ((exptx==BIAS+LDBL_MAX_EXP &&
62 ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)!=0) || /* x is NaN */
63 (expty==BIAS+LDBL_MAX_EXP &&
64 ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* y is NaN */
66 if (expsignx==BIAS && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0)
67 return atanl(y); /* x=1.0 */
68 m = ((expsigny>>15)&1)|((expsignx>>14)&2); /* 2*sign(x)+sign(y) */
71 if(expty==0 && ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)==0) {
74 case 1: return y; /* atan(+-0,+anything)=+-0 */
75 case 2: return pi+tiny;/* atan(+0,-anything) = pi */
76 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
80 if(exptx==0 && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0)
81 return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny;
84 if(exptx==BIAS+LDBL_MAX_EXP) {
85 if(expty==BIAS+LDBL_MAX_EXP) {
87 case 0: return pio2_hi*0.5+tiny;/* atan(+INF,+INF) */
88 case 1: return -pio2_hi*0.5-tiny;/* atan(-INF,+INF) */
89 case 2: return 1.5*pio2_hi+tiny;/*atan(+INF,-INF)*/
90 case 3: return -1.5*pio2_hi-tiny;/*atan(-INF,-INF)*/
94 case 0: return zero ; /* atan(+...,+INF) */
95 case 1: return -zero ; /* atan(-...,+INF) */
96 case 2: return pi+tiny ; /* atan(+...,-INF) */
97 case 3: return -pi-tiny ; /* atan(-...,-INF) */
102 if(expty==BIAS+LDBL_MAX_EXP)
103 return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny;
107 if(k > LDBL_MANT_DIG+2) { /* |y/x| huge */
111 else if(expsignx<0&&k<-LDBL_MANT_DIG-2) z=0.0; /* |y/x| tiny, x<0 */
112 else z=atanl(fabsl(y/x)); /* safe to do y/x */
114 case 0: return z ; /* atan(+,+) */
115 case 1: return -z ; /* atan(-,+) */
116 case 2: return pi-(z-pi_lo);/* atan(+,-) */
117 default: /* case 3 */
118 return (z-pi_lo)-pi;/* atan(-,-) */