73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
/*
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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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/*
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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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int64_t i0,sx;
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int32_t j0;
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EXTRACT_WORDS64(i0,x);
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sx = (i0>>63)&1;
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j0 = ((i0>>52)&0x7ff)-0x3ff;
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if(j0<52) {
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if(j0<0) {
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if((i0 & UINT64_C(0x7fffffffffffffff))==0) return x;
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uint64_t i = i0 & UINT64_C(0xfffffffffffff);
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i0 &= UINT64_C(0xfffe000000000000);
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i0 |= (((i|-i) >> 12) & UINT64_C(0x8000000000000));
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INSERT_WORDS64(x,i0);
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double w = TWO52[sx]+x;
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double t = w-TWO52[sx];
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EXTRACT_WORDS64(i0,t);
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INSERT_WORDS64(t,(i0&UINT64_C(0x7fffffffffffffff))|(sx<<63));
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return t;
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} else {
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uint64_t i = UINT64_C(0x000fffffffffffff)>>j0;
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if((i0&i)==0) return x; /* x is integral */
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i>>=1;
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if((i0&i)!=0)
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i0 = (i0&(~i))|(UINT64_C(0x4000000000000)>>j0);
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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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INSERT_WORDS64(x,i0);
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double w = TWO52[sx]+x;
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return w-TWO52[sx];
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}
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#ifndef __rint
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weak_alias (__rint, rint)
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# ifdef NO_LONG_DOUBLE
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strong_alias (__rint, __rintl)
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weak_alias (__rint, rintl)
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# endif
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#endif
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