e_rem_pio2f.c revision 176558
181464Sbrian/* e_rem_pio2f.c -- float version of e_rem_pio2.c 281464Sbrian * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 381464Sbrian * Debugged and optimized by Bruce D. Evans. 481464Sbrian */ 581464Sbrian 629841Sbrian/* 729841Sbrian * ==================================================== 881464Sbrian * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 981464Sbrian * 1081464Sbrian * Developed at SunPro, a Sun Microsystems, Inc. business. 1181464Sbrian * Permission to use, copy, modify, and distribute this 1281464Sbrian * software is freely granted, provided that this notice 1381464Sbrian * is preserved. 1481464Sbrian * ==================================================== 1581464Sbrian */ 1629841Sbrian 1781464Sbrian#include <sys/cdefs.h> 1881464Sbrian__FBSDID("$FreeBSD: head/lib/msun/src/e_rem_pio2f.c 176558 2008-02-25 18:28:58Z bde $"); 1981464Sbrian 2081464Sbrian/* __ieee754_rem_pio2f(x,y) 2181464Sbrian * 2281464Sbrian * return the remainder of x rem pi/2 in *y 2381464Sbrian * use double precision for everything except passing x 2481464Sbrian * use __kernel_rem_pio2() for large x 2581464Sbrian */ 2681464Sbrian 2781464Sbrian#include <float.h> 2830715Sbrian 2950479Speter#include "math.h" 3029841Sbrian#include "math_private.h" 3129841Sbrian 3244106Sbrian/* 3358040Sbrian * invpio2: 53 bits of 2/pi 3457451Smarkm * pio2_1: first 33 bit of pi/2 3568344Sbrian * pio2_1t: pi/2 - pio2_1 3658040Sbrian */ 3775212Sbrian 3868344Sbrianstatic const double 3996387Sbrianhalf = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */ 4096387Sbrianinvpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */ 4196387Sbrianpio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */ 4258040Sbrianpio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */ 4396387Sbrian 4468344Sbrianint 4558040Sbrian__ieee754_rem_pio2f(float x, double *y) 4667910Sbrian{ 4730715Sbrian double w,r,fn; 4829841Sbrian double tx[1],ty[1]; 4929841Sbrian float z; 5029841Sbrian int32_t e0,n,ix,hx; 5167910Sbrian 5267910Sbrian GET_FLOAT_WORD(hx,x); 5367910Sbrian ix = hx&0x7fffffff; 5467910Sbrian /* 33+53 bit pi is good enough for medium size */ 5567910Sbrian if(ix<=0x49490f80) { /* |x| ~<= 2^19*(pi/2), medium size */ 5667910Sbrian /* Use a specialized rint() to get fn. Assume round-to-nearest. */ 5767910Sbrian STRICT_ASSIGN(double,fn,x*invpio2+0x1.8p52); 5867910Sbrian fn = fn-0x1.8p52; 5967910Sbrian#ifdef HAVE_EFFICIENT_IRINT 6067910Sbrian n = irint(fn); 6167910Sbrian#else 6267910Sbrian n = (int32_t)fn; 6367910Sbrian#endif 6467910Sbrian r = x-fn*pio2_1; 6567910Sbrian w = fn*pio2_1t; 6667910Sbrian *y = r-w; 6767910Sbrian return n; 6867910Sbrian } 6967910Sbrian /* 7067910Sbrian * all other (large) arguments 7129841Sbrian */ 7229841Sbrian if(ix>=0x7f800000) { /* x is inf or NaN */ 7336285Sbrian *y=x-x; return 0; 7429841Sbrian } 7529841Sbrian /* set z = scalbn(|x|,ilogb(|x|)-23) */ 7629841Sbrian e0 = (ix>>23)-150; /* e0 = ilogb(|x|)-23; */ 7736285Sbrian SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23))); 7829841Sbrian tx[0] = z; 7967912Sbrian n = __kernel_rem_pio2(tx,ty,e0,1,0); 8067912Sbrian if(hx<0) {*y = -ty[0]; return -n;} 8129841Sbrian *y = ty[0]; return n; 8229841Sbrian} 8329841Sbrian