patch-2.4.4 linux/arch/mips/math-emu/sp_sqrt.c

• Lines: 116
• Date: Fri Apr 13 20:26:07 2001
• Orig file: v2.4.3/linux/arch/mips/math-emu/sp_sqrt.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.3/linux/arch/mips/math-emu/sp_sqrt.c linux/arch/mips/math-emu/sp_sqrt.c
@@ -0,0 +1,115 @@
+/* IEEE754 floating point arithmetic
+ * single precision square root
+ */
+/*
+ * MIPS floating point support
+ * Copyright (C) 1994-2000 Algorithmics Ltd.  All rights reserved.
+ * http://www.algor.co.uk
+ *
+ * ########################################################################
+ *
+ *  This program is free software; you can distribute it and/or modify it
+ *  under the terms of the GNU General Public License (Version 2) as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * ########################################################################
+ */
+
+
+#include "ieee754sp.h"
+
+static const struct ieee754sp_konst knan = {
+	0, SP_EBIAS + SP_EMAX + 1, 0
+};
+
+#define nan	((ieee754sp)knan)
+
+ieee754sp ieee754sp_sqrt(ieee754sp x)
+{
+	int sign = (int) 0x80000000;
+	int ix, s, q, m, t, i;
+	unsigned int r;
+	COMPXDP;
+
+	/* take care of Inf and NaN */
+
+	EXPLODEXDP;
+
+	/* x == INF or NAN? */
+	switch (xc) {
+	case IEEE754_CLASS_QNAN:
+	case IEEE754_CLASS_SNAN:
+		/* sqrt(Nan) = Nan */
+		return ieee754sp_nanxcpt(x, "sqrt");
+	case IEEE754_CLASS_ZERO:
+		/* sqrt(0) = 0 */
+		return x;
+	case IEEE754_CLASS_INF:
+		if (xs)
+			/* sqrt(-Inf) = Nan */
+			return ieee754sp_nanxcpt(nan, "sqrt");
+		/* sqrt(+Inf) = Inf */
+		return x;
+	case IEEE754_CLASS_DNORM:
+	case IEEE754_CLASS_NORM:
+		if (xs)
+			/* sqrt(-x) = Nan */
+			return ieee754sp_nanxcpt(nan, "sqrt");
+		break;
+	}
+
+	ix = x.bits;
+
+	/* normalize x */
+	m = (ix >> 23);
+	if (m == 0) {		/* subnormal x */
+		for (i = 0; (ix & 0x00800000) == 0; i++)
+			ix <<= 1;
+		m -= i - 1;
+	}
+	m -= 127;		/* unbias exponent */
+	ix = (ix & 0x007fffff) | 0x00800000;
+	if (m & 1)		/* odd m, double x to make it even */
+		ix += ix;
+	m >>= 1;		/* m = [m/2] */
+
+	/* generate sqrt(x) bit by bit */
+	ix += ix;
+	q = s = 0;		/* q = sqrt(x) */
+	r = 0x01000000;		/* r = moving bit from right to left */
+
+	while (r != 0) {
+		t = s + r;
+		if (t <= ix) {
+			s = t + r;
+			ix -= t;
+			q += r;
+		}
+		ix += ix;
+		r >>= 1;
+	}
+
+	if (ix != 0) {
+		switch (ieee754_csr.rm) {
+		case IEEE754_RP:
+			q += 2;
+			break;
+		case IEEE754_RN:
+			q += (q & 1);
+			break;
+		}
+	}
+	ix = (q >> 1) + 0x3f000000;
+	ix += (m << 23);
+	x.bits = ix;
+	return x;
+}