99 lines
3.1 KiB
C
99 lines
3.1 KiB
C
/* e_rem_pio2f.c -- float version of e_rem_pio2.c
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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* Debugged and optimized by Bruce D. Evans.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#ifndef lint
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static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_rem_pio2f.c,v 1.19 2005/11/23 03:03:09 bde Exp $";
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#endif
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/* __ieee754_rem_pio2f(x,y)
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*
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* return the remainder of x rem pi/2 in y[0]+y[1]
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* use double precision internally
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* use __kernel_rem_pio2() for large x
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*/
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#include "math.h"
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#include "math_private.h"
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/*
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* Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi
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*/
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static const int32_t two_over_pi[] = {
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0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62,
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0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A,
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0x424DD2, 0xE00649, 0x2EEA09, 0xD1921C, 0xFE1DEB, 0x1CB129,
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0xA73EE8, 0x8235F5, 0x2EBB44, 0x84E99C, 0x7026B4, 0x5F7E41,
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0x3991D6, 0x398353, 0x39F49C, 0x845F8B, 0xBDF928, 0x3B1FF8,
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0x97FFDE, 0x05980F, 0xEF2F11, 0x8B5A0A, 0x6D1F6D, 0x367ECF,
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0x27CB09, 0xB74F46, 0x3F669E, 0x5FEA2D, 0x7527BA, 0xC7EBE5,
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0xF17B3D, 0x0739F7, 0x8A5292, 0xEA6BFB, 0x5FB11F, 0x8D5D08,
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0x560330, 0x46FC7B, 0x6BABF0, 0xCFBC20, 0x9AF436, 0x1DA9E3,
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0x91615E, 0xE61B08, 0x659985, 0x5F14A0, 0x68408D, 0xFFD880,
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0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B,
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};
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/*
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* invpio2: 53 bits of 2/pi
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* pio2_1: first 33 bit of pi/2
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* pio2_1t: pi/2 - pio2_1
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*/
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static const double
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zero = 0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */
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half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */
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two24 = 1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */
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invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
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pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */
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pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */
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int32_t __ieee754_rem_pio2f(float x, float *y)
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{
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double w,t,r,fn;
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double tx[1],ty[2];
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float z;
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int32_t e0,n,ix,hx;
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GET_FLOAT_WORD(hx,x);
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ix = hx&0x7fffffff;
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/* 33+53 bit pi is good enough for medium size */
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if(ix<=0x49490f80) { /* |x| ~<= 2^19*(pi/2), medium size */
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t = fabsf(x);
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n = (int32_t) (t*invpio2+half);
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fn = (double)n;
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r = t-fn*pio2_1;
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w = fn*pio2_1t;
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y[0] = r-w;
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y[1] = (r-y[0])-w;
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if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
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else return n;
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}
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/*
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* all other (large) arguments
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*/
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if(ix>=0x7f800000) { /* x is inf or NaN */
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y[0]=y[1]=x-x; return 0;
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}
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/* set z = scalbn(|x|,ilogb(|x|)-23) */
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e0 = (ix>>23)-150; /* e0 = ilogb(|x|)-23; */
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SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23)));
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tx[0] = z;
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n = __kernel_rem_pio2(tx,ty,e0,1,1,two_over_pi);
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y[0] = ty[0];
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y[1] = ty[0] - y[0];
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if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
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return n;
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}
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