patch-2.4.20 linux-2.4.20/arch/mips64/math-emu/dp_sqrt.c

• Lines: 168
• Date: Wed Dec 31 16:00:00 1969
• Orig file: linux-2.4.19/arch/mips64/math-emu/dp_sqrt.c
• Orig date: Mon Jul 2 13:56:40 2001

diff -urN linux-2.4.19/arch/mips64/math-emu/dp_sqrt.c linux-2.4.20/arch/mips64/math-emu/dp_sqrt.c
@@ -1,167 +0,0 @@
-/* IEEE754 floating point arithmetic
- * double 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 "ieee754dp.h"
-
-static const struct ieee754dp_konst knan = {
-#if (defined(BYTE_ORDER) && BYTE_ORDER == LITTLE_ENDIAN) || defined(__MIPSEL__)
-	0, 0, DP_EBIAS + DP_EMAX + 1, 0
-#else
-	0, DP_EBIAS + DP_EMAX + 1, 0, 0
-#endif
-};
-
-#define nan	((ieee754dp)knan)
-
-static const unsigned table[] = {
-	0, 1204, 3062, 5746, 9193, 13348, 18162, 23592,
-	29598, 36145, 43202, 50740, 58733, 67158, 75992,
-	85215, 83599, 71378, 60428, 50647, 41945, 34246,
-	27478, 21581, 16499, 12183, 8588, 5674, 3403,
-	1742, 661, 130
-};
-
-ieee754dp ieee754dp_sqrt(ieee754dp x)
-{
-	struct ieee754_csr oldcsr;
-	ieee754dp y, z, t;
-	unsigned scalx, yh;
-	COMPXDP;
-
-	EXPLODEXDP;
-
-	/* x == INF or NAN? */
-	switch (xc) {
-	case IEEE754_CLASS_QNAN:
-	case IEEE754_CLASS_SNAN:
-		/* sqrt(Nan) = Nan */
-		return ieee754dp_nanxcpt(x, "sqrt");
-	case IEEE754_CLASS_ZERO:
-		/* sqrt(0) = 0 */
-		return x;
-	case IEEE754_CLASS_INF:
-		if (xs)
-			/* sqrt(-Inf) = Nan */
-			return ieee754dp_nanxcpt(nan, "sqrt");
-		/* sqrt(+Inf) = Inf */
-		return x;
-	case IEEE754_CLASS_DNORM:
-		DPDNORMX;
-		/* fall through */
-	case IEEE754_CLASS_NORM:
-		if (xs)
-			/* sqrt(-x) = Nan */
-			return ieee754dp_nanxcpt(nan, "sqrt");
-		break;
-	}
-
-	/* save old csr; switch off INX enable & flag; set RN rounding */
-	oldcsr = ieee754_csr;
-	ieee754_csr.mx &= ~IEEE754_INEXACT;
-	ieee754_csr.sx &= ~IEEE754_INEXACT;
-	ieee754_csr.rm = IEEE754_RN;
-
-	/* adjust exponent to prevent overflow */
-	scalx = 0;
-	if (xe > 512) {		/* x > 2**-512? */
-		xe -= 512;	/* x = x / 2**512 */
-		scalx += 256;
-	} else if (xe < -512) {	/* x < 2**-512? */
-		xe += 512;	/* x = x * 2**512 */
-		scalx -= 256;
-	}
-
-	y = x = builddp(0, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
-
-	/* magic initial approximation to almost 8 sig. bits */
-	yh = y.bits >> 32;
-	yh = (yh >> 1) + 0x1ff80000;
-	yh = yh - table[(yh >> 15) & 31];
-	y.bits = ((unsigned long long) yh << 32) | (y.bits & 0xffffffff);
-
-	/* Heron's rule once with correction to improve to ~18 sig. bits */
-	/* t=x/y; y=y+t; py[n0]=py[n0]-0x00100006; py[n1]=0; */
-	t = ieee754dp_div(x, y);
-	y = ieee754dp_add(y, t);
-	y.bits -= 0x0010000600000000LL;
-	y.bits &= 0xffffffff00000000LL;
-
-	/* triple to almost 56 sig. bits: y ~= sqrt(x) to within 1 ulp */
-	/* t=y*y; z=t;  pt[n0]+=0x00100000; t+=z; z=(x-z)*y; */
-	z = t = ieee754dp_mul(y, y);
-	t.parts.bexp += 0x001;
-	t = ieee754dp_add(t, z);
-	z = ieee754dp_mul(ieee754dp_sub(x, z), y);
-
-	/* t=z/(t+x) ;  pt[n0]+=0x00100000; y+=t; */
-	t = ieee754dp_div(z, ieee754dp_add(t, x));
-	t.parts.bexp += 0x001;
-	y = ieee754dp_add(y, t);
-
-	/* twiddle last bit to force y correctly rounded */
-
-	/* set RZ, clear INEX flag */
-	ieee754_csr.rm = IEEE754_RZ;
-	ieee754_csr.sx &= ~IEEE754_INEXACT;
-
-	/* t=x/y; ...chopped quotient, possibly inexact */
-	t = ieee754dp_div(x, y);
-
-	if (ieee754_csr.sx & IEEE754_INEXACT || t.bits != y.bits) {
-
-		if (!(ieee754_csr.sx & IEEE754_INEXACT))
-			/* t = t-ulp */
-			t.bits -= 1;
-
-		/* add inexact to result status */
-		oldcsr.cx |= IEEE754_INEXACT;
-		oldcsr.sx |= IEEE754_INEXACT;
-
-		switch (oldcsr.rm) {
-		case IEEE754_RP:
-			y.bits += 1;
-			/* drop through */
-		case IEEE754_RN:
-			t.bits += 1;
-			break;
-		}
-
-		/* y=y+t; ...chopped sum */
-		y = ieee754dp_add(y, t);
-
-		/* adjust scalx for correctly rounded sqrt(x) */
-		scalx -= 1;
-	}
-
-	/* py[n0]=py[n0]+scalx; ...scale back y */
-	y.parts.bexp += scalx;
-
-	/* restore rounding mode, possibly set inexact */
-	ieee754_csr = oldcsr;
-
-	return y;
-}