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>
18 * See comments in e_atan2.c.
19 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
26 #include "math_private.h"
28 static volatile long double
30 static const long double
34 /* XXX Work around the fact that gcc truncates long double constants on i386 */
35 static volatile double
36 pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */
37 pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */
38 #define pi ((long double)pi1 + pi2)
40 static const long double
41 pi = 3.14159265358979323846264338327950280e+00L;
45 atan2l(long double y, long double x)
47 union IEEEl2bits ux, uy;
50 int16_t exptx, expsignx, expty, expsigny;
53 expsigny = uy.xbits.expsign;
54 expty = expsigny & 0x7fff;
56 expsignx = ux.xbits.expsign;
57 exptx = expsignx & 0x7fff;
59 if ((exptx==BIAS+LDBL_MAX_EXP &&
60 ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)!=0) || /* x is NaN */
61 (expty==BIAS+LDBL_MAX_EXP &&
62 ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* y is NaN */
64 if (expsignx==BIAS && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0)
65 return atanl(y); /* x=1.0 */
66 m = ((expsigny>>15)&1)|((expsignx>>14)&2); /* 2*sign(x)+sign(y) */
69 if(expty==0 && ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)==0) {
72 case 1: return y; /* atan(+-0,+anything)=+-0 */
73 case 2: return pi+tiny;/* atan(+0,-anything) = pi */
74 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
78 if(exptx==0 && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0)
79 return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny;
82 if(exptx==BIAS+LDBL_MAX_EXP) {
83 if(expty==BIAS+LDBL_MAX_EXP) {
85 case 0: return pio2_hi*0.5+tiny;/* atan(+INF,+INF) */
86 case 1: return -pio2_hi*0.5-tiny;/* atan(-INF,+INF) */
87 case 2: return 1.5*pio2_hi+tiny;/*atan(+INF,-INF)*/
88 case 3: return -1.5*pio2_hi-tiny;/*atan(-INF,-INF)*/
92 case 0: return zero ; /* atan(+...,+INF) */
93 case 1: return -zero ; /* atan(-...,+INF) */
94 case 2: return pi+tiny ; /* atan(+...,-INF) */
95 case 3: return -pi-tiny ; /* atan(-...,-INF) */
100 if(expty==BIAS+LDBL_MAX_EXP)
101 return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny;
105 if(k > LDBL_MANT_DIG+2) { /* |y/x| huge */
109 else if(expsignx<0&&k<-LDBL_MANT_DIG-2) z=0.0; /* |y/x| tiny, x<0 */
110 else z=atanl(fabsl(y/x)); /* safe to do y/x */
112 case 0: return z ; /* atan(+,+) */
113 case 1: return -z ; /* atan(-,+) */
114 case 2: return pi-(z-pi_lo);/* atan(+,-) */
115 default: /* case 3 */
116 return (z-pi_lo)-pi;/* atan(-,-) */