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/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* rint(x)
* Return x rounded to integral value according to the prevailing
* rounding mode.
* Method:
* Using floating addition.
* Exception:
* Inexact flag raised if x not equal to rint(x).
*/
#include "math.h"
#include "math_private.h"
static const double
TWO52[2]={
4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
};
double rint(double x)
{
int32_t i0, j0, sx;
u_int32_t i,i1;
double t;
/* We use w = x + 2^52; t = w - 2^52; trick to round x to integer.
* This trick requires that compiler does not optimize it
* by keeping intermediate result w in a register wider than double.
* Declaring w volatile assures that value gets truncated to double
* (unfortunately, it also forces store+load):
*/
volatile double w;
EXTRACT_WORDS(i0,i1,x);
/* Unbiased exponent */
j0 = ((((u_int32_t)i0) >> 20)&0x7ff)-0x3ff;
if (j0 > 51) {
//Why bother? Just returning x works too
//if (j0 == 0x400) /* inf or NaN */
// return x+x;
return x; /* x is integral */
}
/* Sign */
sx = ((u_int32_t)i0) >> 31;
if (j0<20) {
if (j0<0) { /* |x| < 1 */
if (((i0&0x7fffffff)|i1)==0) return x;
i1 |= (i0&0x0fffff);
i0 &= 0xfffe0000;
i0 |= ((i1|-i1)>>12)&0x80000;
SET_HIGH_WORD(x,i0);
w = TWO52[sx]+x;
t = w-TWO52[sx];
GET_HIGH_WORD(i0,t);
SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
return t;
} else {
i = (0x000fffff)>>j0;
if (((i0&i)|i1)==0) return x; /* x is integral */
i>>=1;
if (((i0&i)|i1)!=0) {
if (j0==19) i1 = 0x40000000;
else i0 = (i0&(~i))|((0x20000)>>j0);
}
}
} else {
i = ((u_int32_t)(0xffffffff))>>(j0-20);
if ((i1&i)==0) return x; /* x is integral */
i>>=1;
if ((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
}
INSERT_WORDS(x,i0,i1);
w = TWO52[sx]+x;
return w-TWO52[sx];
}
libm_hidden_def(rint)
strong_alias(rint, nearbyint)
libm_hidden_def(nearbyint)
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