1*1e651e1eSRoland Levillain 2*1e651e1eSRoland Levillain /* @(#)s_rint.c 1.3 95/01/18 */ 3*1e651e1eSRoland Levillain /* 4*1e651e1eSRoland Levillain * ==================================================== 5*1e651e1eSRoland Levillain * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6*1e651e1eSRoland Levillain * 7*1e651e1eSRoland Levillain * Developed at SunSoft, a Sun Microsystems, Inc. business. 8*1e651e1eSRoland Levillain * Permission to use, copy, modify, and distribute this 9*1e651e1eSRoland Levillain * software is freely granted, provided that this notice 10*1e651e1eSRoland Levillain * is preserved. 11*1e651e1eSRoland Levillain * ==================================================== 12*1e651e1eSRoland Levillain */ 13*1e651e1eSRoland Levillain 14*1e651e1eSRoland Levillain /* 15*1e651e1eSRoland Levillain * ieee_rint(x) 16*1e651e1eSRoland Levillain * Return x rounded to integral value according to the prevailing 17*1e651e1eSRoland Levillain * rounding mode. 18*1e651e1eSRoland Levillain * Method: 19*1e651e1eSRoland Levillain * Using floating addition. 20*1e651e1eSRoland Levillain * Exception: 21*1e651e1eSRoland Levillain * Inexact flag raised if x not equal to ieee_rint(x). 22*1e651e1eSRoland Levillain */ 23*1e651e1eSRoland Levillain 24*1e651e1eSRoland Levillain #include "fdlibm.h" 25*1e651e1eSRoland Levillain 26*1e651e1eSRoland Levillain #ifdef __STDC__ 27*1e651e1eSRoland Levillain static const double 28*1e651e1eSRoland Levillain #else 29*1e651e1eSRoland Levillain static double 30*1e651e1eSRoland Levillain #endif 31*1e651e1eSRoland Levillain TWO52[2]={ 32*1e651e1eSRoland Levillain 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ 33*1e651e1eSRoland Levillain -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ 34*1e651e1eSRoland Levillain }; 35*1e651e1eSRoland Levillain 36*1e651e1eSRoland Levillain #ifdef __STDC__ ieee_rint(double x)37*1e651e1eSRoland Levillain double ieee_rint(double x) 38*1e651e1eSRoland Levillain #else 39*1e651e1eSRoland Levillain double ieee_rint(x) 40*1e651e1eSRoland Levillain double x; 41*1e651e1eSRoland Levillain #endif 42*1e651e1eSRoland Levillain { 43*1e651e1eSRoland Levillain int i0,j0,sx; 44*1e651e1eSRoland Levillain unsigned i,i1; 45*1e651e1eSRoland Levillain double w,t; 46*1e651e1eSRoland Levillain i0 = __HI(x); 47*1e651e1eSRoland Levillain sx = (i0>>31)&1; 48*1e651e1eSRoland Levillain i1 = __LO(x); 49*1e651e1eSRoland Levillain j0 = ((i0>>20)&0x7ff)-0x3ff; 50*1e651e1eSRoland Levillain if(j0<20) { 51*1e651e1eSRoland Levillain if(j0<0) { 52*1e651e1eSRoland Levillain if(((i0&0x7fffffff)|i1)==0) return x; 53*1e651e1eSRoland Levillain i1 |= (i0&0x0fffff); 54*1e651e1eSRoland Levillain i0 &= 0xfffe0000; 55*1e651e1eSRoland Levillain i0 |= ((i1|-i1)>>12)&0x80000; 56*1e651e1eSRoland Levillain __HI(x)=i0; 57*1e651e1eSRoland Levillain w = TWO52[sx]+x; 58*1e651e1eSRoland Levillain t = w-TWO52[sx]; 59*1e651e1eSRoland Levillain i0 = __HI(t); 60*1e651e1eSRoland Levillain __HI(t) = (i0&0x7fffffff)|(sx<<31); 61*1e651e1eSRoland Levillain return t; 62*1e651e1eSRoland Levillain } else { 63*1e651e1eSRoland Levillain i = (0x000fffff)>>j0; 64*1e651e1eSRoland Levillain if(((i0&i)|i1)==0) return x; /* x is integral */ 65*1e651e1eSRoland Levillain i>>=1; 66*1e651e1eSRoland Levillain if(((i0&i)|i1)!=0) { 67*1e651e1eSRoland Levillain if(j0==19) i1 = 0x40000000; else 68*1e651e1eSRoland Levillain i0 = (i0&(~i))|((0x20000)>>j0); 69*1e651e1eSRoland Levillain } 70*1e651e1eSRoland Levillain } 71*1e651e1eSRoland Levillain } else if (j0>51) { 72*1e651e1eSRoland Levillain if(j0==0x400) return x+x; /* inf or NaN */ 73*1e651e1eSRoland Levillain else return x; /* x is integral */ 74*1e651e1eSRoland Levillain } else { 75*1e651e1eSRoland Levillain i = ((unsigned)(0xffffffff))>>(j0-20); 76*1e651e1eSRoland Levillain if((i1&i)==0) return x; /* x is integral */ 77*1e651e1eSRoland Levillain i>>=1; 78*1e651e1eSRoland Levillain if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); 79*1e651e1eSRoland Levillain } 80*1e651e1eSRoland Levillain __HI(x) = i0; 81*1e651e1eSRoland Levillain __LO(x) = i1; 82*1e651e1eSRoland Levillain w = TWO52[sx]+x; 83*1e651e1eSRoland Levillain return w-TWO52[sx]; 84*1e651e1eSRoland Levillain } 85