/* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ /* * rint(x) * Return x rounded to integral value according to the prevailing * rounding mode. * Method: * Using floating addition. * Exception: * Inexact flag raised if x not equal to rint(x). */ #include "math.h" #include "math_private.h" static const double TWO52[2]={ 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ }; double rint(double x) { int32_t i0, j0, sx; u_int32_t i,i1; double t; /* We use w = x + 2^52; t = w - 2^52; trick to round x to integer. * This trick requires that compiler does not optimize it * by keeping intermediate result w in a register wider than double. * Declaring w volatile assures that value gets truncated to double * (unfortunately, it also forces store+load): */ volatile double w; EXTRACT_WORDS(i0,i1,x); /* Unbiased exponent */ j0 = ((((u_int32_t)i0) >> 20)&0x7ff)-0x3ff; if (j0 > 51) { //Why bother? Just returning x works too //if (j0 == 0x400) /* inf or NaN */ // return x+x; return x; /* x is integral */ } /* Sign */ sx = ((u_int32_t)i0) >> 31; if (j0<20) { if (j0<0) { /* |x| < 1 */ if (((i0&0x7fffffff)|i1)==0) return x; i1 |= (i0&0x0fffff); i0 &= 0xfffe0000; i0 |= ((i1|-i1)>>12)&0x80000; SET_HIGH_WORD(x,i0); w = TWO52[sx]+x; t = w-TWO52[sx]; GET_HIGH_WORD(i0,t); SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); return t; } else { i = (0x000fffff)>>j0; if (((i0&i)|i1)==0) return x; /* x is integral */ i>>=1; if (((i0&i)|i1)!=0) { if (j0==19) i1 = 0x40000000; else i0 = (i0&(~i))|((0x20000)>>j0); } } } else { i = ((u_int32_t)(0xffffffff))>>(j0-20); if ((i1&i)==0) return x; /* x is integral */ i>>=1; if ((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); } INSERT_WORDS(x,i0,i1); w = TWO52[sx]+x; return w-TWO52[sx]; } libm_hidden_def(rint) strong_alias(rint, nearbyint) libm_hidden_def(nearbyint)