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 "cdefs-compat.h" 18 //__FBSDID("$FreeBSD: src/lib/msun/src/e_rem_pio2f.c,v 1.32 2009/06/03 08:16:34 ed Exp $"); 19 20 /* __ieee754_rem_pio2f(x,y) 21 * 22 * return the remainder of x rem pi/2 in *y 23 * use double precision for everything except passing x 24 * use __kernel_rem_pio2() for large x 25 */ 26 27 #include <float.h> 28 #include <openlibm_math.h> 29 30 #include "math_private.h" 31 32 /* 33 * invpio2: 53 bits of 2/pi 34 * pio2_1: first 33 bit of pi/2 35 * pio2_1t: pi/2 - pio2_1 36 */ 37 38 static const double 39 invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */ 40 pio2_1 = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */ 41 pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */ 42 43 __inline int 44 __ieee754_rem_pio2f(float x, double *y) 45 { 46 double w,r,fn; 47 double tx[1],ty[1]; 48 float z; 49 int32_t e0,n,ix,hx; 50 51 GET_FLOAT_WORD(hx,x); 52 ix = hx&0x7fffffff; 53 /* 33+53 bit pi is good enough for medium size */ 54 if(ix<0x4dc90fdb) { /* |x| ~< 2^28*(pi/2), medium size */ 55 /* Use a specialized rint() to get fn. Assume round-to-nearest. */ 56 STRICT_ASSIGN(double,fn,x*invpio2+0x1.8p52); 57 fn = fn-0x1.8p52; 58 #ifdef HAVE_EFFICIENT_IRINT 59 n = irint(fn); 60 #else 61 n = (int32_t)fn; 62 #endif 63 r = x-fn*pio2_1; 64 w = fn*pio2_1t; 65 *y = r-w; 66 return n; 67 } 68 /* 69 * all other (large) arguments 70 */ 71 if(ix>=0x7f800000) { /* x is inf or NaN */ 72 *y=x-x; return 0; 73 } 74 /* set z = scalbn(|x|,ilogb(|x|)-23) */ 75 e0 = (ix>>23)-150; /* e0 = ilogb(|x|)-23; */ 76 SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23))); 77 tx[0] = z; 78 n = __kernel_rem_pio2(tx,ty,e0,1,0); 79 if(hx<0) {*y = -ty[0]; return -n;} 80 *y = ty[0]; return n; 81 } 82