linux_kernel/arch/mips/math-emu/sp_fdp.c

/* IEEE754 floating point arithmetic
 * single precision
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.
 *
 *  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.,
 *  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
 */

#include "ieee754sp.h"
#include "ieee754dp.h"

union ieee754sp ieee754sp_fdp(union ieee754dp x)
{
	u32 rm;

	COMPXDP;
	union ieee754sp nan;

	EXPLODEXDP;

	ieee754_clearcx();

	FLUSHXDP;

	switch (xc) {
	case IEEE754_CLASS_SNAN:
		ieee754_setcx(IEEE754_INVALID_OPERATION);
		return ieee754sp_nanxcpt(ieee754sp_indef());

	case IEEE754_CLASS_QNAN:
		nan = buildsp(xs, SP_EMAX + 1 + SP_EBIAS, (u32)
				(xm >> (DP_FBITS - SP_FBITS)));
		if (!ieee754sp_isnan(nan))
			nan = ieee754sp_indef();
		return ieee754sp_nanxcpt(nan);

	case IEEE754_CLASS_INF:
		return ieee754sp_inf(xs);

	case IEEE754_CLASS_ZERO:
		return ieee754sp_zero(xs);

	case IEEE754_CLASS_DNORM:
		/* can't possibly be sp representable */
		ieee754_setcx(IEEE754_UNDERFLOW);
		ieee754_setcx(IEEE754_INEXACT);
		if ((ieee754_csr.rm == FPU_CSR_RU && !xs) ||
				(ieee754_csr.rm == FPU_CSR_RD && xs))
			return ieee754sp_mind(xs);
		return ieee754sp_zero(xs);

	case IEEE754_CLASS_NORM:
		break;
	}

	/*
	 * Convert from DP_FBITS to SP_FBITS+3 with sticky right shift.
	 */
	rm = (xm >> (DP_FBITS - (SP_FBITS + 3))) |
	     ((xm << (64 - (DP_FBITS - (SP_FBITS + 3)))) != 0);

	return ieee754sp_format(xs, xe, rm);
}