1 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2 *
3 * ***** BEGIN LICENSE BLOCK *****
4 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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6 * The contents of this file are subject to the Mozilla Public License Version
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14 * License.
15 *
16 * The Original Code is Mozilla Communicator client code, released
17 * March 31, 1998.
18 *
19 * The Initial Developer of the Original Code is
20 * Sun Microsystems, Inc.
21 * Portions created by the Initial Developer are Copyright (C) 1998
22 * the Initial Developer. All Rights Reserved.
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25 *
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40 /* @(#)e_rem_pio2.c 1.4 95/01/18 */
41 /*
42 * ====================================================
43 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
44 *
45 * Developed at SunSoft, a Sun Microsystems, Inc. business.
46 * Permission to use, copy, modify, and distribute this
47 * software is freely granted, provided that this notice
48 * is preserved.
49 * ====================================================
50 *
51 */
53 /* __ieee754_rem_pio2(x,y)
54 *
55 * return the remainder of x rem pi/2 in y[0]+y[1]
56 * use __kernel_rem_pio2()
57 */
59 #include "fdlibm.h"
61 /*
62 * Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi
63 */
64 #ifdef __STDC__
65 static const int two_over_pi[] = {
66 #else
67 static int two_over_pi[] = {
68 #endif
69 0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62,
70 0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A,
71 0x424DD2, 0xE00649, 0x2EEA09, 0xD1921C, 0xFE1DEB, 0x1CB129,
72 0xA73EE8, 0x8235F5, 0x2EBB44, 0x84E99C, 0x7026B4, 0x5F7E41,
73 0x3991D6, 0x398353, 0x39F49C, 0x845F8B, 0xBDF928, 0x3B1FF8,
74 0x97FFDE, 0x05980F, 0xEF2F11, 0x8B5A0A, 0x6D1F6D, 0x367ECF,
75 0x27CB09, 0xB74F46, 0x3F669E, 0x5FEA2D, 0x7527BA, 0xC7EBE5,
76 0xF17B3D, 0x0739F7, 0x8A5292, 0xEA6BFB, 0x5FB11F, 0x8D5D08,
77 0x560330, 0x46FC7B, 0x6BABF0, 0xCFBC20, 0x9AF436, 0x1DA9E3,
78 0x91615E, 0xE61B08, 0x659985, 0x5F14A0, 0x68408D, 0xFFD880,
79 0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B,
80 };
82 #ifdef __STDC__
83 static const int npio2_hw[] = {
84 #else
85 static int npio2_hw[] = {
86 #endif
87 0x3FF921FB, 0x400921FB, 0x4012D97C, 0x401921FB, 0x401F6A7A, 0x4022D97C,
88 0x4025FDBB, 0x402921FB, 0x402C463A, 0x402F6A7A, 0x4031475C, 0x4032D97C,
89 0x40346B9C, 0x4035FDBB, 0x40378FDB, 0x403921FB, 0x403AB41B, 0x403C463A,
90 0x403DD85A, 0x403F6A7A, 0x40407E4C, 0x4041475C, 0x4042106C, 0x4042D97C,
91 0x4043A28C, 0x40446B9C, 0x404534AC, 0x4045FDBB, 0x4046C6CB, 0x40478FDB,
92 0x404858EB, 0x404921FB,
93 };
95 /*
96 * invpio2: 53 bits of 2/pi
97 * pio2_1: first 33 bit of pi/2
98 * pio2_1t: pi/2 - pio2_1
99 * pio2_2: second 33 bit of pi/2
100 * pio2_2t: pi/2 - (pio2_1+pio2_2)
101 * pio2_3: third 33 bit of pi/2
102 * pio2_3t: pi/2 - (pio2_1+pio2_2+pio2_3)
103 */
105 #ifdef __STDC__
106 static const double
107 #else
108 static double
109 #endif
110 zero = 0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */
111 half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */
112 two24 = 1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */
113 invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
114 pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */
115 pio2_1t = 6.07710050650619224932e-11, /* 0x3DD0B461, 0x1A626331 */
116 pio2_2 = 6.07710050630396597660e-11, /* 0x3DD0B461, 0x1A600000 */
117 pio2_2t = 2.02226624879595063154e-21, /* 0x3BA3198A, 0x2E037073 */
118 pio2_3 = 2.02226624871116645580e-21, /* 0x3BA3198A, 0x2E000000 */
119 pio2_3t = 8.47842766036889956997e-32; /* 0x397B839A, 0x252049C1 */
121 #ifdef __STDC__
122 int __ieee754_rem_pio2(double x, double *y)
123 #else
124 int __ieee754_rem_pio2(x,y)
125 double x,y[];
126 #endif
127 {
128 fd_twoints u, ux, uz;
129 double z,w,t,r,fn;
130 double tx[3];
131 int e0,i,j,nx,n,ix,hx;
133 u.d = x;
134 hx = __HI(u); /* high word of x */
135 ix = hx&0x7fffffff;
136 if(ix<=0x3fe921fb) /* |x| ~<= pi/4 , no need for reduction */
137 {y[0] = x; y[1] = 0; return 0;}
138 if(ix<0x4002d97c) { /* |x| < 3pi/4, special case with n=+-1 */
139 if(hx>0) {
140 z = x - pio2_1;
141 if(ix!=0x3ff921fb) { /* 33+53 bit pi is good enough */
142 y[0] = z - pio2_1t;
143 y[1] = (z-y[0])-pio2_1t;
144 } else { /* near pi/2, use 33+33+53 bit pi */
145 z -= pio2_2;
146 y[0] = z - pio2_2t;
147 y[1] = (z-y[0])-pio2_2t;
148 }
149 return 1;
150 } else { /* negative x */
151 z = x + pio2_1;
152 if(ix!=0x3ff921fb) { /* 33+53 bit pi is good enough */
153 y[0] = z + pio2_1t;
154 y[1] = (z-y[0])+pio2_1t;
155 } else { /* near pi/2, use 33+33+53 bit pi */
156 z += pio2_2;
157 y[0] = z + pio2_2t;
158 y[1] = (z-y[0])+pio2_2t;
159 }
160 return -1;
161 }
162 }
163 if(ix<=0x413921fb) { /* |x| ~<= 2^19*(pi/2), medium size */
164 t = fd_fabs(x);
165 n = (int) (t*invpio2+half);
166 fn = (double)n;
167 r = t-fn*pio2_1;
168 w = fn*pio2_1t; /* 1st round good to 85 bit */
169 if(n<32&&ix!=npio2_hw[n-1]) {
170 y[0] = r-w; /* quick check no cancellation */
171 } else {
172 j = ix>>20;
173 y[0] = r-w;
174 u.d = y[0];
175 i = j-(((__HI(u))>>20)&0x7ff);
176 if(i>16) { /* 2nd iteration needed, good to 118 */
177 t = r;
178 w = fn*pio2_2;
179 r = t-w;
180 w = fn*pio2_2t-((t-r)-w);
181 y[0] = r-w;
182 u.d = y[0];
183 i = j-(((__HI(u))>>20)&0x7ff);
184 if(i>49) { /* 3rd iteration need, 151 bits acc */
185 t = r; /* will cover all possible cases */
186 w = fn*pio2_3;
187 r = t-w;
188 w = fn*pio2_3t-((t-r)-w);
189 y[0] = r-w;
190 }
191 }
192 }
193 y[1] = (r-y[0])-w;
194 if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
195 else return n;
196 }
197 /*
198 * all other (large) arguments
199 */
200 if(ix>=0x7ff00000) { /* x is inf or NaN */
201 y[0]=y[1]=x-x; return 0;
202 }
203 /* set z = scalbn(|x|,ilogb(x)-23) */
204 ux.d = x; uz.d = z;
205 __LO(uz) = __LO(ux);
206 z = uz.d;
207 e0 = (ix>>20)-1046; /* e0 = ilogb(z)-23; */
208 uz.d = z;
209 __HI(uz) = ix - (e0<<20);
210 z = uz.d;
211 for(i=0;i<2;i++) {
212 tx[i] = (double)((int)(z));
213 z = (z-tx[i])*two24;
214 }
215 tx[2] = z;
216 nx = 3;
217 while(tx[nx-1]==zero) nx--; /* skip zero term */
218 n = __kernel_rem_pio2(tx,y,e0,nx,2,two_over_pi);
219 if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
220 return n;
221 }