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- /* @(#)e_rem_pio2.c 5.1 93/09/24 */
- /*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
- #if defined(LIBM_SCCS) && !defined(lint)
- static char rcsid[] = "$NetBSD: e_rem_pio2.c,v 1.8 1995/05/10 20:46:02 jtc Exp $";
- #endif
- /* __ieee754_rem_pio2(x,y)
- *
- * return the remainder of x rem pi/2 in y[0]+y[1]
- * use __kernel_rem_pio2()
- */
- #include "math.h"
- #include "math_private.h"
- libm_hidden_proto(fabs)
- /*
- * Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi
- */
- #ifdef __STDC__
- static const int32_t two_over_pi[] = {
- #else
- static int32_t two_over_pi[] = {
- #endif
- 0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62,
- 0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A,
- 0x424DD2, 0xE00649, 0x2EEA09, 0xD1921C, 0xFE1DEB, 0x1CB129,
- 0xA73EE8, 0x8235F5, 0x2EBB44, 0x84E99C, 0x7026B4, 0x5F7E41,
- 0x3991D6, 0x398353, 0x39F49C, 0x845F8B, 0xBDF928, 0x3B1FF8,
- 0x97FFDE, 0x05980F, 0xEF2F11, 0x8B5A0A, 0x6D1F6D, 0x367ECF,
- 0x27CB09, 0xB74F46, 0x3F669E, 0x5FEA2D, 0x7527BA, 0xC7EBE5,
- 0xF17B3D, 0x0739F7, 0x8A5292, 0xEA6BFB, 0x5FB11F, 0x8D5D08,
- 0x560330, 0x46FC7B, 0x6BABF0, 0xCFBC20, 0x9AF436, 0x1DA9E3,
- 0x91615E, 0xE61B08, 0x659985, 0x5F14A0, 0x68408D, 0xFFD880,
- 0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B,
- };
- #ifdef __STDC__
- static const int32_t npio2_hw[] = {
- #else
- static int32_t npio2_hw[] = {
- #endif
- 0x3FF921FB, 0x400921FB, 0x4012D97C, 0x401921FB, 0x401F6A7A, 0x4022D97C,
- 0x4025FDBB, 0x402921FB, 0x402C463A, 0x402F6A7A, 0x4031475C, 0x4032D97C,
- 0x40346B9C, 0x4035FDBB, 0x40378FDB, 0x403921FB, 0x403AB41B, 0x403C463A,
- 0x403DD85A, 0x403F6A7A, 0x40407E4C, 0x4041475C, 0x4042106C, 0x4042D97C,
- 0x4043A28C, 0x40446B9C, 0x404534AC, 0x4045FDBB, 0x4046C6CB, 0x40478FDB,
- 0x404858EB, 0x404921FB,
- };
- /*
- * invpio2: 53 bits of 2/pi
- * pio2_1: first 33 bit of pi/2
- * pio2_1t: pi/2 - pio2_1
- * pio2_2: second 33 bit of pi/2
- * pio2_2t: pi/2 - (pio2_1+pio2_2)
- * pio2_3: third 33 bit of pi/2
- * pio2_3t: pi/2 - (pio2_1+pio2_2+pio2_3)
- */
- #ifdef __STDC__
- static const double
- #else
- static double
- #endif
- zero = 0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */
- half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */
- two24 = 1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */
- invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
- pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */
- pio2_1t = 6.07710050650619224932e-11, /* 0x3DD0B461, 0x1A626331 */
- pio2_2 = 6.07710050630396597660e-11, /* 0x3DD0B461, 0x1A600000 */
- pio2_2t = 2.02226624879595063154e-21, /* 0x3BA3198A, 0x2E037073 */
- pio2_3 = 2.02226624871116645580e-21, /* 0x3BA3198A, 0x2E000000 */
- pio2_3t = 8.47842766036889956997e-32; /* 0x397B839A, 0x252049C1 */
- #ifdef __STDC__
- int32_t attribute_hidden __ieee754_rem_pio2(double x, double *y)
- #else
- int32_t attribute_hidden __ieee754_rem_pio2(x,y)
- double x,y[];
- #endif
- {
- double z=0.0,w,t,r,fn;
- double tx[3];
- int32_t e0,i,j,nx,n,ix,hx;
- u_int32_t low;
- GET_HIGH_WORD(hx,x); /* high word of x */
- ix = hx&0x7fffffff;
- if(ix<=0x3fe921fb) /* |x| ~<= pi/4 , no need for reduction */
- {y[0] = x; y[1] = 0; return 0;}
- if(ix<0x4002d97c) { /* |x| < 3pi/4, special case with n=+-1 */
- if(hx>0) {
- z = x - pio2_1;
- if(ix!=0x3ff921fb) { /* 33+53 bit pi is good enough */
- y[0] = z - pio2_1t;
- y[1] = (z-y[0])-pio2_1t;
- } else { /* near pi/2, use 33+33+53 bit pi */
- z -= pio2_2;
- y[0] = z - pio2_2t;
- y[1] = (z-y[0])-pio2_2t;
- }
- return 1;
- } else { /* negative x */
- z = x + pio2_1;
- if(ix!=0x3ff921fb) { /* 33+53 bit pi is good enough */
- y[0] = z + pio2_1t;
- y[1] = (z-y[0])+pio2_1t;
- } else { /* near pi/2, use 33+33+53 bit pi */
- z += pio2_2;
- y[0] = z + pio2_2t;
- y[1] = (z-y[0])+pio2_2t;
- }
- return -1;
- }
- }
- if(ix<=0x413921fb) { /* |x| ~<= 2^19*(pi/2), medium size */
- t = fabs(x);
- n = (int32_t) (t*invpio2+half);
- fn = (double)n;
- r = t-fn*pio2_1;
- w = fn*pio2_1t; /* 1st round good to 85 bit */
- if(n<32&&ix!=npio2_hw[n-1]) {
- y[0] = r-w; /* quick check no cancellation */
- } else {
- u_int32_t high;
- j = ix>>20;
- y[0] = r-w;
- GET_HIGH_WORD(high,y[0]);
- i = j-((high>>20)&0x7ff);
- if(i>16) { /* 2nd iteration needed, good to 118 */
- t = r;
- w = fn*pio2_2;
- r = t-w;
- w = fn*pio2_2t-((t-r)-w);
- y[0] = r-w;
- GET_HIGH_WORD(high,y[0]);
- i = j-((high>>20)&0x7ff);
- if(i>49) { /* 3rd iteration need, 151 bits acc */
- t = r; /* will cover all possible cases */
- w = fn*pio2_3;
- r = t-w;
- w = fn*pio2_3t-((t-r)-w);
- y[0] = r-w;
- }
- }
- }
- y[1] = (r-y[0])-w;
- if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
- else return n;
- }
- /*
- * all other (large) arguments
- */
- if(ix>=0x7ff00000) { /* x is inf or NaN */
- y[0]=y[1]=x-x; return 0;
- }
- /* set z = scalbn(|x|,ilogb(x)-23) */
- GET_LOW_WORD(low,x);
- SET_LOW_WORD(z,low);
- e0 = (ix>>20)-1046; /* e0 = ilogb(z)-23; */
- SET_HIGH_WORD(z, ix - ((int32_t)(e0<<20)));
- for(i=0;i<2;i++) {
- tx[i] = (double)((int32_t)(z));
- z = (z-tx[i])*two24;
- }
- tx[2] = z;
- nx = 3;
- while(tx[nx-1]==zero) nx--; /* skip zero term */
- n = __kernel_rem_pio2(tx,y,e0,nx,2,two_over_pi);
- if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
- return n;
- }
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