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

• Lines: 188
• Date: Fri Apr 13 20:26:07 2001
• Orig file: v2.4.3/linux/arch/mips/math-emu/sp_sub.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.3/linux/arch/mips/math-emu/sp_sub.c linux/arch/mips/math-emu/sp_sub.c
@@ -0,0 +1,187 @@
+/* IEEE754 floating point arithmetic
+ * single precision
+ */
+/*
+ * 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"
+
+ieee754sp ieee754sp_sub(ieee754sp x, ieee754sp y)
+{
+	COMPXSP;
+	COMPYSP;
+
+	CLEARCX;
+
+	EXPLODEXSP;
+	EXPLODEYSP;
+
+	switch (CLPAIR(xc, yc)) {
+	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
+		return ieee754sp_nanxcpt(ieee754sp_bestnan(x, y), "sub", x,
+					 y);
+
+	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
+	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
+	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
+	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
+	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
+		return ieee754sp_nanxcpt(y, "sub", x, y);
+
+	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
+	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
+	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
+	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
+	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
+		return ieee754sp_nanxcpt(x, "sub", x, y);
+
+	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
+		return ieee754sp_bestnan(x, y);
+
+	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
+	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
+	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
+	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
+		return y;
+
+	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
+	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
+	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
+	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
+		return x;
+
+
+		/* Inifity handeling 
+		 */
+
+	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
+		if (xs != ys)
+			return x;
+		SETCX(IEEE754_INVALID_OPERATION);
+		return ieee754sp_xcpt(ieee754sp_indef(), "sub", x, y);
+
+	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
+	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
+	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
+		return ieee754sp_inf(ys ^ 1);
+
+	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
+	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
+	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
+		return x;
+
+		/* Zero handeling 
+		 */
+
+	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
+		if (xs != ys)
+			return x;
+		else
+			return ieee754sp_zero(ieee754_csr.rm ==
+					      IEEE754_RD);
+
+	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
+	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
+		return x;
+
+	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
+	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
+		/* quick fix up */
+		DPSIGN(y) ^= 1;
+		return y;
+
+	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
+		SPDNORMX;
+
+	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
+		SPDNORMY;
+		break;
+
+	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
+		SPDNORMX;
+		break;
+
+	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
+		break;
+	}
+	/* flip sign of y and handle as add */
+	ys ^= 1;
+
+	assert(xm & SP_HIDDEN_BIT);
+	assert(ym & SP_HIDDEN_BIT);
+
+
+	/* provide guard,round and stick bit space */
+	xm <<= 3;
+	ym <<= 3;
+
+	if (xe > ye) {
+		/* have to shift y fraction right to align
+		 */
+		int s = xe - ye;
+		SPXSRSYn(s);
+	} else if (ye > xe) {
+		/* have to shift x fraction right to align
+		 */
+		int s = ye - xe;
+		SPXSRSXn(s);
+	}
+	assert(xe == ye);
+	assert(xe <= SP_EMAX);
+
+	if (xs == ys) {
+		/* generate 28 bit result of adding two 27 bit numbers
+		 */
+		xm = xm + ym;
+		xe = xe;
+		xs = xs;
+
+		if (xm >> (SP_MBITS + 1 + 3)) {	/* carry out */
+			SPXSRSX1();	/* shift preserving sticky */
+		}
+	} else {
+		if (xm >= ym) {
+			xm = xm - ym;
+			xe = xe;
+			xs = xs;
+		} else {
+			xm = ym - xm;
+			xe = xe;
+			xs = ys;
+		}
+		if (xm == 0)
+			if (ieee754_csr.rm == IEEE754_RD)
+				return ieee754sp_zero(1);	/* round negative inf. => sign = -1 */
+			else
+				return ieee754sp_zero(0);	/* other round modes   => sign = 1 */
+
+		/* normalize to rounding precision 
+		 */
+		while ((xm >> (SP_MBITS + 3)) == 0) {
+			xm <<= 1;
+			xe--;
+		}
+	}
+	SPNORMRET2(xs, xe, xm, "sub", x, y);
+}