ack/mach/proto/fp/adder.c

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1988-04-07 11:40:46 +00:00
/*
(c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
See the copyright notice in the ACK home directory, in the file "Copyright".
*/
/* $Header$ */
1988-04-07 10:57:49 +00:00
/*
* these are the routines the routines to do 32 and 64-bit addition
*/
# ifdef DEBUG
# include <stdio.h>
# endif
# include "adder.h"
# define UNKNOWN -1
# define TRUE 1
# define FALSE 0
# define MAXBIT 0x80000000L
/*
* add 64 bits
*/
b64_add(e1,e2)
/*
* pointers to 64 bit 'registers'
*/
register B64 *e1,*e2;
{
register short overflow;
short carry;
/* add higher pair of 32 bits */
overflow = b32_add(&e1->h_32,&e2->h_32);
/* add lower pair of 32 bits */
carry = b32_add(&e1->l_32,&e2->l_32);
# ifdef DEBUG
printf("\t\t\t\t\tb64_add: overflow (%d); internal carry(%d)\n",
overflow,carry);
fflush(stdout);
# endif
if ((carry) && (++e1->h_32 == 0))
return(TRUE); /* had a 64 bit overflow */
else
return(overflow); /* return status from higher add */
}
/*
* add 32 bits (unsigned longs)
* and return the carry status
*/
b32_add(e1,e2)
register unsigned long *e1,*e2;
{
register short carry;
if (*e1 & *e2 & MAXBIT) /* both max_bits are set */
carry = TRUE; /* so there is a carry */
else
carry = ((*e1 | *e2) & MAXBIT)
/* only one is set - might be a carry */
? UNKNOWN
/* both are clear - no carry */
: FALSE;
# ifdef DEBUG
fflush(stdout);
printf("\t\t\t\t\tb32_add: overflow before add(%d) test(%d)\n",
carry,(*e1&MAXBIT)?FALSE:TRUE);
printf("%08X\n%08X\n",*e1,*e2);
# endif
*e1 += *e2;
# ifdef DEBUG
printf("%08X\n",*e1);
fflush(stdout);
# endif
if (carry != UNKNOWN)
return(carry);
else
/*
* if maxbit in answer is set there is no carry
* return the NAND of this bit
*/
return((*e1&MAXBIT)?FALSE:TRUE);
}