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 #include <sys/cdefs.h> 18 __FBSDID("$FreeBSD$"); 19 20 /* __ieee754_rem_pio2f(x,y) 21 * 22 * return the remainder of x rem pi/2 in y[0]+y[1] 23 * use double precision internally 24 * use __kernel_rem_pio2() for large x 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 /* 31 * invpio2: 53 bits of 2/pi 32 * pio2_1: first 33 bit of pi/2 33 * pio2_1t: pi/2 - pio2_1 34 */ 35 36 static const double 37 half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */ 38 invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */ 39 pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */ 40 pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */ 41 42 int 43 __ieee754_rem_pio2f(float x, float *y) 44 { 45 double w,t,r,fn; 46 double tx[1],ty[2]; 47 float z; 48 int32_t e0,n,ix,hx; 49 50 GET_FLOAT_WORD(hx,x); 51 ix = hx&0x7fffffff; 52 /* 33+53 bit pi is good enough for medium size */ 53 if(ix<=0x49490f80) { /* |x| ~<= 2^19*(pi/2), medium size */ 54 t = fabsf(x); 55 n = (int32_t) (t*invpio2+half); 56 fn = (double)n; 57 r = t-fn*pio2_1; 58 w = fn*pio2_1t; 59 y[0] = r-w; 60 y[1] = (r-y[0])-w; 61 if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;} 62 else return n; 63 } 64 /* 65 * all other (large) arguments 66 */ 67 if(ix>=0x7f800000) { /* x is inf or NaN */ 68 y[0]=y[1]=x-x; return 0; 69 } 70 /* set z = scalbn(|x|,ilogb(|x|)-23) */ 71 e0 = (ix>>23)-150; /* e0 = ilogb(|x|)-23; */ 72 SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23))); 73 tx[0] = z; 74 n = __kernel_rem_pio2(tx,ty,e0,1,1); 75 y[0] = ty[0]; 76 y[1] = ty[0] - y[0]; 77 if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;} 78 return n; 79 } 80