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 14 static char rcsid[] = "$FreeBSD$"; 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 static const long double 38 TWO52[2]={ 39 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ 40 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ 41 }; 42 43 double 44 __generic_rint(double x) 45 { 46 int32_t i0,j0,sx; 47 u_int32_t i,i1; 48 double w,t; 49 EXTRACT_WORDS(i0,i1,x); 50 sx = (i0>>31)&1; 51 j0 = ((i0>>20)&0x7ff)-0x3ff; 52 if(j0<20) { 53 if(j0<0) { 54 if(((i0&0x7fffffff)|i1)==0) return x; 55 i1 |= (i0&0x0fffff); 56 i0 &= 0xfffe0000; 57 i0 |= ((i1|-i1)>>12)&0x80000; 58 SET_HIGH_WORD(x,i0); 59 w = TWO52[sx]+x; 60 t = w-TWO52[sx]; 61 GET_HIGH_WORD(i0,t); 62 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 63 return t; 64 } else { 65 i = (0x000fffff)>>j0; 66 if(((i0&i)|i1)==0) return x; /* x is integral */ 67 i>>=1; 68 if(((i0&i)|i1)!=0) { 69 if(j0==19) i1 = 0x40000000; else 70 i0 = (i0&(~i))|((0x20000)>>j0); 71 } 72 } 73 } else if (j0>51) { 74 if(j0==0x400) return x+x; /* inf or NaN */ 75 else return x; /* x is integral */ 76 } else { 77 i = ((u_int32_t)(0xffffffff))>>(j0-20); 78 if((i1&i)==0) return x; /* x is integral */ 79 i>>=1; 80 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); 81 } 82 INSERT_WORDS(x,i0,i1); 83 w = TWO52[sx]+x; 84 return w-TWO52[sx]; 85 } 86