patch-2.4.20 linux-2.4.20/arch/parisc/math-emu/sfsqrt.c

• Lines: 188
• Date: Thu Nov 28 15:53:10 2002
• Orig file: linux-2.4.19/arch/parisc/math-emu/sfsqrt.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/parisc/math-emu/sfsqrt.c linux-2.4.20/arch/parisc/math-emu/sfsqrt.c
@@ -0,0 +1,187 @@
+/*
+ * Linux/PA-RISC Project (http://www.parisc-linux.org/)
+ *
+ * Floating-point emulation code
+ *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
+ *
+ *    This program is free software; you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation; either version 2, or (at your option)
+ *    any later version.
+ *
+ *    This program is distributed in the hope that 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+/*
+ * BEGIN_DESC
+ *
+ *  File:
+ *	@(#)	pa/spmath/sfsqrt.c		$Revision: 1.1 $
+ *
+ *  Purpose:
+ *	Single Floating-point Square Root
+ *
+ *  External Interfaces:
+ *	sgl_fsqrt(srcptr,nullptr,dstptr,status)
+ *
+ *  Internal Interfaces:
+ *
+ *  Theory:
+ *	<<please update with a overview of the operation of this file>>
+ *
+ * END_DESC
+*/
+
+
+#include "float.h"
+#include "sgl_float.h"
+
+/*
+ *  Single Floating-point Square Root
+ */
+
+/*ARGSUSED*/
+unsigned int
+sgl_fsqrt(
+    sgl_floating_point *srcptr,
+    unsigned int *nullptr,
+    sgl_floating_point *dstptr,
+    unsigned int *status)
+{
+	register unsigned int src, result;
+	register int src_exponent;
+	register unsigned int newbit, sum;
+	register boolean guardbit = FALSE, even_exponent;
+
+	src = *srcptr;
+        /*
+         * check source operand for NaN or infinity
+         */
+        if ((src_exponent = Sgl_exponent(src)) == SGL_INFINITY_EXPONENT) {
+                /*
+                 * is signaling NaN?
+                 */
+                if (Sgl_isone_signaling(src)) {
+                        /* trap if INVALIDTRAP enabled */
+                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+                        /* make NaN quiet */
+                        Set_invalidflag();
+                        Sgl_set_quiet(src);
+                }
+                /*
+                 * Return quiet NaN or positive infinity.
+		 *  Fall thru to negative test if negative infinity.
+                 */
+		if (Sgl_iszero_sign(src) || Sgl_isnotzero_mantissa(src)) {
+                	*dstptr = src;
+                	return(NOEXCEPTION);
+		}
+        }
+
+        /*
+         * check for zero source operand
+         */
+	if (Sgl_iszero_exponentmantissa(src)) {
+		*dstptr = src;
+		return(NOEXCEPTION);
+	}
+
+        /*
+         * check for negative source operand 
+         */
+	if (Sgl_isone_sign(src)) {
+		/* trap if INVALIDTRAP enabled */
+		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+		/* make NaN quiet */
+		Set_invalidflag();
+		Sgl_makequietnan(src);
+		*dstptr = src;
+		return(NOEXCEPTION);
+	}
+
+	/*
+	 * Generate result
+	 */
+	if (src_exponent > 0) {
+		even_exponent = Sgl_hidden(src);
+		Sgl_clear_signexponent_set_hidden(src);
+	}
+	else {
+		/* normalize operand */
+		Sgl_clear_signexponent(src);
+		src_exponent++;
+		Sgl_normalize(src,src_exponent);
+		even_exponent = src_exponent & 1;
+	}
+	if (even_exponent) {
+		/* exponent is even */
+		/* Add comment here.  Explain why odd exponent needs correction */
+		Sgl_leftshiftby1(src);
+	}
+	/*
+	 * Add comment here.  Explain following algorithm.
+	 * 
+	 * Trust me, it works.
+	 *
+	 */
+	Sgl_setzero(result);
+	newbit = 1 << SGL_P;
+	while (newbit && Sgl_isnotzero(src)) {
+		Sgl_addition(result,newbit,sum);
+		if(sum <= Sgl_all(src)) {
+			/* update result */
+			Sgl_addition(result,(newbit<<1),result);
+			Sgl_subtract(src,sum,src);
+		}
+		Sgl_rightshiftby1(newbit);
+		Sgl_leftshiftby1(src);
+	}
+	/* correct exponent for pre-shift */
+	if (even_exponent) {
+		Sgl_rightshiftby1(result);
+	}
+
+	/* check for inexact */
+	if (Sgl_isnotzero(src)) {
+		if (!even_exponent && Sgl_islessthan(result,src)) 
+			Sgl_increment(result);
+		guardbit = Sgl_lowmantissa(result);
+		Sgl_rightshiftby1(result);
+
+		/*  now round result  */
+		switch (Rounding_mode()) {
+		case ROUNDPLUS:
+		     Sgl_increment(result);
+		     break;
+		case ROUNDNEAREST:
+		     /* stickybit is always true, so guardbit 
+		      * is enough to determine rounding */
+		     if (guardbit) {
+			Sgl_increment(result);
+		     }
+		     break;
+		}
+		/* increment result exponent by 1 if mantissa overflowed */
+		if (Sgl_isone_hiddenoverflow(result)) src_exponent+=2;
+
+		if (Is_inexacttrap_enabled()) {
+			Sgl_set_exponent(result,
+			 ((src_exponent-SGL_BIAS)>>1)+SGL_BIAS);
+			*dstptr = result;
+			return(INEXACTEXCEPTION);
+		}
+		else Set_inexactflag();
+	}
+	else {
+		Sgl_rightshiftby1(result);
+	}
+	Sgl_set_exponent(result,((src_exponent-SGL_BIAS)>>1)+SGL_BIAS);
+	*dstptr = result;
+	return(NOEXCEPTION);
+}