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70 lines
1.7 KiB
C
70 lines
1.7 KiB
C
/* Adapted for use as nearbyint by Ulrich Drepper <drepper@cygnus.com>. */
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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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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: s_rint.c,v 1.8 1995/05/10 20:48:04 jtc 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 <fenv.h>
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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 __nearbyint(double x)
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{
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fenv_t env;
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int32_t i0,j0,sx;
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double w,t;
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GET_HIGH_WORD(i0,x);
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sx = (i0>>31)&1;
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j0 = ((i0>>20)&0x7ff)-0x3ff;
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if(j0<52) {
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if(j0<0) {
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feholdexcept (&env);
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w = TWO52[sx]+x;
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t = w-TWO52[sx];
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fesetenv (&env);
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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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}
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} else {
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if(j0==0x400) return x+x; /* inf or NaN */
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else return x; /* x is integral */
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}
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feholdexcept (&env);
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w = TWO52[sx]+x;
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t = w-TWO52[sx];
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fesetenv (&env);
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return t;
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}
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weak_alias (__nearbyint, nearbyint)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__nearbyint, __nearbyintl)
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weak_alias (__nearbyint, nearbyintl)
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#endif
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