/*  (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.  See the copyright notice in the ACK home directory, in the file "Copyright".*//* $Header: /cvsup/minix/src/lib/ack/fphook/mul_ext.fc,v 1.1 2005/10/10 15:27:44 beng Exp $ *//*	ROUTINE TO MULTIPLY TWO EXTENDED FORMAT NUMBERS*/# include "FP_bias.h"# include "FP_trap.h"# include "FP_types.h"# include "FP_shift.h"voidmul_ext(e1,e2)EXTEND	*e1,*e2;{	register int	i,j;		/* loop control	*/	unsigned short	mp[4];		/* multiplier */	unsigned short	mc[4];		/* multipcand */	unsigned short	result[8];	/* result */	register unsigned short *pres;	/* first save the sign (XOR)			*/	e1->sign ^= e2->sign;	/* compute new exponent */	e1->exp += e2->exp + 1;	/* 128 bit multiply of mantissas			*/		/* assign unknown long formats		*/		/* to known unsigned word formats	*/	mp[0] = e1->m1 >> 16;	mp[1] = (unsigned short) e1->m1;	mp[2] = e1->m2 >> 16;	mp[3] = (unsigned short) e1->m2;	mc[0] = e2->m1 >> 16;	mc[1] = (unsigned short) e2->m1;	mc[2] = e2->m2 >> 16;	mc[3] = (unsigned short) e2->m2;	for (i = 8; i--;) {		result[i] = 0;	}	/*	 *	fill registers with their components	 */	for(i=4, pres = &result[4];i--;pres--) if (mp[i]) {		unsigned short k = 0;		unsigned long mpi = mp[i];		for(j=4;j--;) {			unsigned long tmp = (unsigned long)pres[j] + k;			if (mc[j]) tmp += mpi * mc[j];			pres[j] = tmp;			k = tmp >> 16;		}		pres[-1] = k;	}        if (! (result[0] & 0x8000)) {                e1->exp--;                for (i = 0; i <= 3; i++) {                        result[i] <<= 1;                        if (result[i+1]&0x8000) result[i] |= 1;                }                result[4] <<= 1;        }	/*	 *	combine the registers to a total	 */	e1->m1 = ((unsigned long)(result[0]) << 16) + result[1];	e1->m2 = ((unsigned long)(result[2]) << 16) + result[3];	if (result[4] & 0x8000) {		if (++e1->m2 == 0)			if (++e1->m1 == 0) {				e1->m1 = NORMBIT;				e1->exp++;			}	}					/* check for overflow	*/	if (e1->exp >= EXT_MAX)	{		trap(EFOVFL);			/* if caught 			*/			/* return signed infinity	*/		e1->exp = EXT_MAX;infinity:	e1->m1 = e1->m2 =0L;		return;	}				/* check for underflow	*/	if (e1->exp < EXT_MIN)	{		trap(EFUNFL);		e1->exp = EXT_MIN;		goto infinity;	}}