Initial revision

mach/proto/fp/adder.c

@@ -0,0 +1,81 @@
+/*
+ *	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);
+}