upload sdk

git-svn-id: svn://kolibrios.org@4349 a494cfbc-eb01-0410-851d-a64ba20cac60

contrib/sdk/sources/newlib/math/s_rint.c

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+
+/* @(#)s_rint.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+/*
+FUNCTION
+<<rint>>, <<rintf>>--round to integer
+INDEX
+	rint
+INDEX
+	rintf
+
+ANSI_SYNOPSIS
+	#include <math.h>
+	double rint(double <[x]>);
+	float rintf(float <[x]>);
+
+DESCRIPTION
+	The <<rint>> functions round their argument to an integer value in
+	floating-point format, using the current rounding direction.  They
+	raise the "inexact" floating-point exception if the result differs
+	in value from the argument.  See the <<nearbyint>> functions for the
+	same function with the "inexact" floating-point exception never being
+	raised.  Newlib does not directly support floating-point exceptions.
+	The <<rint>> functions are written so that the "inexact" exception is
+	raised in hardware implementations that support it, even though Newlib
+	does not provide access.
+
+RETURNS
+<[x]> rounded to an integral value, using the current rounding direction.
+
+PORTABILITY
+ANSI C, POSIX
+
+SEEALSO
+<<nearbyint>>, <<round>>
+
+*/
+
+/*
+ * rint(x)
+ * Return x rounded to integral value according to the prevailing
+ * rounding mode.
+ * Method:
+ *	Using floating addition.
+ *	Whenever a fraction is present, if the second or any following bit after
+ *	the radix point is set, limit to the second radix point to avoid
+ *	possible double rounding in the TWO52 +- steps (in case guard bits are
+ *	used).  Specifically, if have any, chop off bits past the 2nd place and
+ *	set the second place.
+ *	(e.g.	2.0625=0b10.0001 => 0b10.01=2.25;
+ *		2.3125=0b10.011  => 0b10.01=2.25;
+ *		1.5625= 0b1.1001 =>  0b1.11=1.75;
+ *		1.9375= 0b1.1111 =>  0b1.11=1.75.
+ *	Pseudo-code:  if(x.frac & ~0b0.10) x.frac = (x.frac & 0b0.11) | 0b0.01;).
+ * Exception:
+ *	Inexact flag raised if x not equal to rint(x).
+ */
+
+#include "fdlibm.h"
+
+#ifndef _DOUBLE_IS_32BITS
+
+#ifdef __STDC__
+static const double
+#else
+static double 
+#endif
+TWO52[2]={
+  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
+ -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
+};
+
+#ifdef __STDC__
+	double rint(double x)
+#else
+	double rint(x)
+	double x;
+#endif
+{
+	__int32_t i0,j0,sx;
+	__uint32_t i,i1;
+	double t;
+	volatile double w;
+	EXTRACT_WORDS(i0,i1,x);
+	sx = (i0>>31)&1;		/* sign */
+	j0 = ((i0>>20)&0x7ff)-0x3ff;	/* exponent */
+	if(j0<20) {			/* no integral bits in LS part */
+	    if(j0<0) { 			/* x is fractional or 0 */
+		if(((i0&0x7fffffff)|i1)==0) return x;	/* x == 0 */
+		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 {			/* x has integer and maybe fraction */
+		i = (0x000fffff)>>j0;
+		if(((i0&i)|i1)==0) return x; /* x is integral */
+		i>>=1;
+		if(((i0&i)|i1)!=0) {
+		    /* 2nd or any later bit after radix is set */
+		    if(j0==19) i1 = 0x80000000; else i1 = 0;
+		    i0 = (i0&(~i))|((0x40000)>>j0);
+		}
+	    }
+	} else if (j0>51) {
+	    if(j0==0x400) return x+x;	/* inf or NaN */
+	    else return x;		/* x is integral */
+	} else {
+	    i = ((__uint32_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];
+}
+
+#endif /* _DOUBLE_IS_32BITS */