s_rint.c revision 22993
1/* @(#)s_rint.c 5.1 93/09/24 */ 2/* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13#ifndef lint 14static char rcsid[] = "$Id$"; 15#endif 16 17/* 18 * rint(x) 19 * Return x rounded to integral value according to the prevailing 20 * rounding mode. 21 * Method: 22 * Using floating addition. 23 * Exception: 24 * Inexact flag raised if x not equal to rint(x). 25 */ 26 27#include "math.h" 28#include "math_private.h" 29 30/* 31 * TWO23 is long double instead of double to avoid a bug in gcc. Without 32 * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have double 33 * precision and doesn't clip them to double precision when they are 34 * assigned and returned. Use long double even in the !__STDC__ case in 35 * case this is compiled with gcc -traditional. 36 */ 37#ifdef __STDC__ 38static const long double 39#else 40static long double 41#endif 42TWO52[2]={ 43 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ 44 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ 45}; 46 47#ifdef __STDC__ 48 double __generic_rint(double x) 49#else 50 double __generic_rint(x) 51 double x; 52#endif 53{ 54 int32_t i0,j0,sx; 55 u_int32_t i,i1; 56 double w,t; 57 EXTRACT_WORDS(i0,i1,x); 58 sx = (i0>>31)&1; 59 j0 = ((i0>>20)&0x7ff)-0x3ff; 60 if(j0<20) { 61 if(j0<0) { 62 if(((i0&0x7fffffff)|i1)==0) return x; 63 i1 |= (i0&0x0fffff); 64 i0 &= 0xfffe0000; 65 i0 |= ((i1|-i1)>>12)&0x80000; 66 SET_HIGH_WORD(x,i0); 67 w = TWO52[sx]+x; 68 t = w-TWO52[sx]; 69 GET_HIGH_WORD(i0,t); 70 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 71 return t; 72 } else { 73 i = (0x000fffff)>>j0; 74 if(((i0&i)|i1)==0) return x; /* x is integral */ 75 i>>=1; 76 if(((i0&i)|i1)!=0) { 77 if(j0==19) i1 = 0x40000000; else 78 i0 = (i0&(~i))|((0x20000)>>j0); 79 } 80 } 81 } else if (j0>51) { 82 if(j0==0x400) return x+x; /* inf or NaN */ 83 else return x; /* x is integral */ 84 } else { 85 i = ((u_int32_t)(0xffffffff))>>(j0-20); 86 if((i1&i)==0) return x; /* x is integral */ 87 i>>=1; 88 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); 89 } 90 INSERT_WORDS(x,i0,i1); 91 w = TWO52[sx]+x; 92 return w-TWO52[sx]; 93} 94