2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 * Copyright (c) 2008 Steven G. Kargl, David Schultz, Bruce D. Evans.
6 * Developed at SunSoft, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
12 * Optimized by Bruce D. Evans.
15 /* ld80 version of __ieee754_rem_pio2l(x,y)
17 * return the remainder of x rem pi/2 in y[0]+y[1]
18 * use __kernel_rem_pio2()
24 #include "math_private.h"
27 #define BIAS (LDBL_MAX_EXP - 1)
30 * invpio2: 64 bits of 2/pi
31 * pio2_1: first 39 bits of pi/2
32 * pio2_1t: pi/2 - pio2_1
33 * pio2_2: second 39 bits of pi/2
34 * pio2_2t: pi/2 - (pio2_1+pio2_2)
35 * pio2_3: third 39 bits of pi/2
36 * pio2_3t: pi/2 - (pio2_1+pio2_2+pio2_3)
40 zero = 0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */
41 two24 = 1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */
42 pio2_1 = 1.57079632679597125389e+00, /* 0x3FF921FB, 0x54444000 */
43 pio2_2 = -1.07463465549783099519e-12, /* -0x12e7b967674000.0p-92 */
44 pio2_3 = 6.36831716351370313614e-25; /* 0x18a2e037074000.0p-133 */
46 #if defined(__amd64__) || defined(__i386__)
47 /* Long double constants are slow on these arches, and broken on i386. */
48 static const volatile double
49 invpio2hi = 6.3661977236758138e-01, /* 0x145f306dc9c883.0p-53 */
50 invpio2lo = -3.9356538861223811e-17, /* -0x16b00000000000.0p-107 */
51 pio2_1thi = -1.0746346554971943e-12, /* -0x12e7b9676733af.0p-92 */
52 pio2_1tlo = 8.8451028997905949e-29, /* 0x1c080000000000.0p-146 */
53 pio2_2thi = 6.3683171635109499e-25, /* 0x18a2e03707344a.0p-133 */
54 pio2_2tlo = 2.3183081793789774e-41, /* 0x10280000000000.0p-187 */
55 pio2_3thi = -2.7529965190440717e-37, /* -0x176b7ed8fbbacc.0p-174 */
56 pio2_3tlo = -4.2006647512740502e-54; /* -0x19c00000000000.0p-230 */
57 #define invpio2 ((long double)invpio2hi + invpio2lo)
58 #define pio2_1t ((long double)pio2_1thi + pio2_1tlo)
59 #define pio2_2t ((long double)pio2_2thi + pio2_2tlo)
60 #define pio2_3t ((long double)pio2_3thi + pio2_3tlo)
62 static const long double
63 invpio2 = 6.36619772367581343076e-01L, /* 0xa2f9836e4e44152a.0p-64 */
64 pio2_1t = -1.07463465549719416346e-12L, /* -0x973dcb3b399d747f.0p-103 */
65 pio2_2t = 6.36831716351095013979e-25L, /* 0xc51701b839a25205.0p-144 */
66 pio2_3t = -2.75299651904407171810e-37L; /* -0xbb5bf6c7ddd660ce.0p-185 */
69 static inline __always_inline int
70 __ieee754_rem_pio2l(long double x, long double *y)
72 union IEEEl2bits u,u1;
73 long double z,w,t,r,fn;
79 expsign = u.xbits.expsign;
80 ex = expsign & 0x7fff;
81 if (ex < BIAS + 25 || (ex == BIAS + 25 && u.bits.manh < 0xc90fdaa2)) {
82 /* |x| ~< 2^25*(pi/2), medium size */
83 fn = rnintl(x*invpio2);
86 w = fn*pio2_1t; /* 1st round good to 102 bit */
93 ex1 = u2.xbits.expsign & 0x7fff;
95 if(i>22) { /* 2nd iteration needed, good to 141 */
99 w = fn*pio2_2t-((t-r)-w);
102 ex1 = u2.xbits.expsign & 0x7fff;
104 if(i>61) { /* 3rd iteration need, 180 bits acc */
105 t = r; /* will cover all possible cases */
108 w = fn*pio2_3t-((t-r)-w);
117 * all other (large) arguments
119 if(ex==0x7fff) { /* x is inf or NaN */
120 y[0]=y[1]=x-x; return 0;
122 /* set z = scalbn(|x|,ilogb(x)-23) */
124 e0 = ex - BIAS - 23; /* e0 = ilogb(|x|)-23; */
125 u1.xbits.expsign = ex - e0;
128 tx[i] = (double)((int32_t)(z));
133 while(tx[nx-1]==zero) nx--; /* skip zero term */
134 n = __kernel_rem_pio2(tx,ty,e0,nx,2);
135 r = (long double)ty[0] + ty[1];
136 w = ty[1] - (r - ty[0]);
137 if(expsign<0) {y[0] = -r; y[1] = -w; return -n;}
138 y[0] = r; y[1] = w; return n;