| The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 1 | /* e_rem_pio2f.c -- float version of e_rem_pio2.c |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| 3 | * Debugged and optimized by Bruce D. Evans. |
| 4 | */ |
| 5 | |
| 6 | /* |
| 7 | * ==================================================== |
| 8 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 9 | * |
| 10 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
| 11 | * Permission to use, copy, modify, and distribute this |
| 12 | * software is freely granted, provided that this notice |
| 13 | * is preserved. |
| 14 | * ==================================================== |
| 15 | */ |
| 16 | |
| 17 | #ifndef lint |
| 18 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_rem_pio2f.c,v 1.19 2005/11/23 03:03:09 bde Exp $"; |
| 19 | #endif |
| 20 | |
| 21 | /* __ieee754_rem_pio2f(x,y) |
| 22 | * |
| 23 | * return the remainder of x rem pi/2 in y[0]+y[1] |
| 24 | * use double precision internally |
| 25 | * use __kernel_rem_pio2() for large x |
| 26 | */ |
| 27 | |
| 28 | #include "math.h" |
| 29 | #include "math_private.h" |
| 30 | |
| 31 | /* |
| 32 | * Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi |
| 33 | */ |
| 34 | static const int32_t two_over_pi[] = { |
| 35 | 0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62, |
| 36 | 0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A, |
| 37 | 0x424DD2, 0xE00649, 0x2EEA09, 0xD1921C, 0xFE1DEB, 0x1CB129, |
| 38 | 0xA73EE8, 0x8235F5, 0x2EBB44, 0x84E99C, 0x7026B4, 0x5F7E41, |
| 39 | 0x3991D6, 0x398353, 0x39F49C, 0x845F8B, 0xBDF928, 0x3B1FF8, |
| 40 | 0x97FFDE, 0x05980F, 0xEF2F11, 0x8B5A0A, 0x6D1F6D, 0x367ECF, |
| 41 | 0x27CB09, 0xB74F46, 0x3F669E, 0x5FEA2D, 0x7527BA, 0xC7EBE5, |
| 42 | 0xF17B3D, 0x0739F7, 0x8A5292, 0xEA6BFB, 0x5FB11F, 0x8D5D08, |
| 43 | 0x560330, 0x46FC7B, 0x6BABF0, 0xCFBC20, 0x9AF436, 0x1DA9E3, |
| 44 | 0x91615E, 0xE61B08, 0x659985, 0x5F14A0, 0x68408D, 0xFFD880, |
| 45 | 0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B, |
| 46 | }; |
| 47 | |
| 48 | /* |
| 49 | * invpio2: 53 bits of 2/pi |
| 50 | * pio2_1: first 33 bit of pi/2 |
| 51 | * pio2_1t: pi/2 - pio2_1 |
| 52 | */ |
| 53 | |
| 54 | static const double |
| 55 | zero = 0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */ |
| 56 | half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */ |
| 57 | two24 = 1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */ |
| 58 | invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */ |
| 59 | pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */ |
| 60 | pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */ |
| 61 | |
| 62 | int32_t __ieee754_rem_pio2f(float x, float *y) |
| 63 | { |
| 64 | double w,t,r,fn; |
| 65 | double tx[1],ty[2]; |
| 66 | float z; |
| 67 | int32_t e0,n,ix,hx; |
| 68 | |
| 69 | GET_FLOAT_WORD(hx,x); |
| 70 | ix = hx&0x7fffffff; |
| 71 | /* 33+53 bit pi is good enough for medium size */ |
| 72 | if(ix<=0x49490f80) { /* |x| ~<= 2^19*(pi/2), medium size */ |
| 73 | t = fabsf(x); |
| 74 | n = (int32_t) (t*invpio2+half); |
| 75 | fn = (double)n; |
| 76 | r = t-fn*pio2_1; |
| 77 | w = fn*pio2_1t; |
| 78 | y[0] = r-w; |
| 79 | y[1] = (r-y[0])-w; |
| 80 | if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;} |
| 81 | else return n; |
| 82 | } |
| 83 | /* |
| 84 | * all other (large) arguments |
| 85 | */ |
| 86 | if(ix>=0x7f800000) { /* x is inf or NaN */ |
| 87 | y[0]=y[1]=x-x; return 0; |
| 88 | } |
| 89 | /* set z = scalbn(|x|,ilogb(|x|)-23) */ |
| 90 | e0 = (ix>>23)-150; /* e0 = ilogb(|x|)-23; */ |
| 91 | SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23))); |
| 92 | tx[0] = z; |
| 93 | n = __kernel_rem_pio2(tx,ty,e0,1,1,two_over_pi); |
| 94 | y[0] = ty[0]; |
| 95 | y[1] = ty[0] - y[0]; |
| 96 | if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;} |
| 97 | return n; |
| 98 | } |