5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/* @(#)s_rint.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include <sys/cdefs.h>
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#if defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: s_rint.c,v 1.12 2008/04/25 22:21:53 christos Exp $");
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#endif
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/*
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* rint(x)
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* Return x rounded to integral value according to the prevailing
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* rounding mode.
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* Method:
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* Using floating addition.
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* Exception:
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* Inexact flag raised if x not equal to rint(x).
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*/
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#include "math.h"
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#include "math_private.h"
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static const double
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TWO52[2]={
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4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
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-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
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};
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double
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rint(double x)
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{
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int32_t i0,jj0,sx;
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uint32_t i,i1;
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double w,t;
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EXTRACT_WORDS(i0,i1,x);
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sx = (i0>>31)&1;
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jj0 = ((i0>>20)&0x7ff)-0x3ff;
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if(jj0<20) {
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if(jj0<0) {
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if(((i0&0x7fffffff)|i1)==0) return x;
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i1 |= (i0&0x0fffff);
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i0 &= 0xfffe0000;
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i0 |= ((i1|-i1)>>12)&0x80000;
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SET_HIGH_WORD(x,i0);
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w = TWO52[sx]+x;
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t = w-TWO52[sx];
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GET_HIGH_WORD(i0,t);
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SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
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return t;
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} else {
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i = (0x000fffff)>>jj0;
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if(((i0&i)|i1)==0) return x; /* x is integral */
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i>>=1;
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if(((i0&i)|i1)!=0) {
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if(jj0==19) i1 = 0x40000000; else
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i0 = (i0&(~i))|((0x20000)>>jj0);
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}
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}
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} else if (jj0>51) {
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if(jj0==0x400) return x+x; /* inf or NaN */
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else return x; /* x is integral */
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} else {
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i = ((uint32_t)(0xffffffff))>>(jj0-20);
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if((i1&i)==0) return x; /* x is integral */
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i>>=1;
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if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20));
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}
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INSERT_WORDS(x,i0,i1);
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w = TWO52[sx]+x;
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return w-TWO52[sx];
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}
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