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/*[
cmp.c
LOCAL CHAR SccsID[]="@(#)cmp.c 1.5 02/09/94";
CMP CPU functions.
------------------
]*/
#include <insignia.h>
#include <host_def.h>
#include <xt.h>
#include <c_main.h>
#include <c_addr.h>
#include <c_bsic.h>
#include <c_prot.h>
#include <c_seg.h>
#include <c_stack.h>
#include <c_xcptn.h>
#include <c_reg.h>
#include <cmp.h>
/*
=====================================================================
EXTERNAL FUNCTIONS START HERE.
=====================================================================
*/
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
/* Generic - one size fits all 'cmp'. */
/* Generic - one size fits all 'cmps'. */
/* Generic - one size fits all 'scas'. */
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
GLOBAL VOID
CMP
IFN3(
IU32, op1, /* lsrc operand */
IU32, op2, /* rsrc operand */
IUM8, op_sz /* 8, 16 or 32-bit */
)
{
IU32 result;
IU32 carry;
IU32 msb;
IU32 op1_msb;
IU32 op2_msb;
IU32 res_msb;
msb = SZ2MSB(op_sz);
result = op1 - op2 & SZ2MASK(op_sz); /* Do operation */
op1_msb = (op1 & msb) != 0; /* Isolate all msb's */
op2_msb = (op2 & msb) != 0;
res_msb = (result & msb) != 0;
carry = op1 ^ op2 ^ result; /* Isolate carries */
/* Determine flags */
/*
OF = (op1 == !op2) & (op1 ^ res)
ie if operand signs differ and res sign different to original
destination set OF.
*/
SET_OF((op1_msb != op2_msb) & (op1_msb ^ res_msb));
/*
Formally:- CF = !op1 & op2 | res & !op1 | res & op2
Equivalently:- CF = OF ^ op1 ^ op2 ^ res
*/
SET_CF(((carry & msb) != 0) ^ GET_OF());
SET_PF(pf_table[result & BYTE_MASK]);
SET_ZF(result == 0);
SET_SF((result & msb) != 0); /* SF = MSB */
SET_AF((carry & BIT4_MASK) != 0); /* AF = Bit 4 carry */
}
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