e_rem_pio2f.cpp (1977B)
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 23 * use double precision for everything except passing x 24 * use __kernel_rem_pio2() for large x 25 */ 26 27 #include <float.h> 28 29 #include "math_private.h" 30 31 /* 32 * invpio2: 53 bits of 2/pi 33 * pio2_1: first 25 bits of pi/2 34 * pio2_1t: pi/2 - pio2_1 35 */ 36 37 static const double 38 invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */ 39 pio2_1 = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */ 40 pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */ 41 42 #ifdef INLINE_REM_PIO2F 43 static inline 44 #endif 45 int 46 __ieee754_rem_pio2f(float x, double *y) 47 { 48 double w,r,fn; 49 double tx[1],ty[1]; 50 float z; 51 int32_t e0,n,ix,hx; 52 53 GET_FLOAT_WORD(hx,x); 54 ix = hx&0x7fffffff; 55 /* 33+53 bit pi is good enough for medium size */ 56 if(ix<0x4dc90fdb) { /* |x| ~< 2^28*(pi/2), medium size */ 57 fn = rnint((float)x*invpio2); 58 n = irint(fn); 59 r = x-fn*pio2_1; 60 w = fn*pio2_1t; 61 *y = r-w; 62 return n; 63 } 64 /* 65 * all other (large) arguments 66 */ 67 if(ix>=0x7f800000) { /* x is inf or NaN */ 68 *y=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,e0,1,0); 75 if(hx<0) {*y = -ty[0]; return -n;} 76 *y = ty[0]; return n; 77 }