sux.c


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#include <limits.h>
#include "opcode.h"
#include <stdint.h>
uint64_t a; /* Accumulator. */
uint64_t y; /* Y index. */
uint64_t x; /* X index. */
uint64_t ps; /* Processor status. */

uint64_t alu(uint8_t opcode, uint64_t value) {
	uint64_t sum;
	uint8_t carry, vf;
	switch(opcode) {
		/* Add with carry. */
		case ADC:
			sum = a+value+carry;
			vf = (~(a^value) & (a^sum & 0x80));
			carry = (sum < value) ? 1 : 0;
			a |= sum;
			break;
		/* Subtract with carry. */
		case SBC:
			sum = a-value-!carry
			vf = (a^value) & (a^sum) & 0x80;
			carry = (sum > value) ? 1 : 0;
			a |= sum;
			break;


	}
}