107 lines
2.5 KiB
C
107 lines
2.5 KiB
C
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/* @(#)s_lrint.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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/*
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* lrint(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 lrint(x).
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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static const double
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#else
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static double
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#endif
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/* Adding a double, x, to 2^52 will cause the result to be rounded based on
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the fractional part of x, according to the implementation's current rounding
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mode. 2^52 is the smallest double that can be represented using all 52 significant
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digits. */
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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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#ifdef __STDC__
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long int lrint(double x)
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#else
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long int lrint(x)
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double x;
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#endif
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{
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__int32_t i0,j0,sx;
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__uint32_t i1;
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double t;
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volatile double w;
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long int result;
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EXTRACT_WORDS(i0,i1,x);
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/* Extract sign bit. */
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sx = (i0>>31)&1;
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/* Extract exponent field. */
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j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
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if(j0 < 20)
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{
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if(j0 < -1)
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return 0;
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else
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{
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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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/* Detect the all-zeros representation of plus and
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minus zero, which fails the calculation below. */
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if ((i0 & ~(1 << 31)) == 0)
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return 0;
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j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
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i0 &= 0x000fffff;
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i0 |= 0x00100000;
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result = i0 >> (20 - j0);
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}
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}
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else if (j0 < (int)(8 * sizeof (long int)) - 1)
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{
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if (j0 >= 52)
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result = ((long int) i0 << (j0 - 20)) | (i1 << (j0 - 52));
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else
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{
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w = TWO52[sx] + x;
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t = w - TWO52[sx];
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EXTRACT_WORDS (i0, i1, t);
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j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
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i0 &= 0x000fffff;
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i0 |= 0x00100000;
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result = ((long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
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}
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}
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else
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{
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return (long int) x;
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}
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return sx ? -result : result;
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}
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#endif /* _DOUBLE_IS_32BITS */
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