addless_add.c

#include <stdio.h>
#include <stdint.h>

#define ADD_LOBIT(a, b, c) ((a)^(b)^(c))
#define ADD_CARRY(a, b, c) ((a&b)|(b&c)|(c&a))

#define ADD_ROUND(i) \
	c|=ADD_LOBIT((a>>(i))&1,(b>>(i))&1,carry)<<(i); \
	carry=ADD_CARRY((a>>(i))&1,(b>>(i))&1,carry);

#define MUL_ROUND(i) \
	c <<= 1; \
	if ((b<<(i))&(1L<<63)) c = add(c, a);

#define LOOP2(c,i) c(i) c(i|1)
#define LOOP4(c,i) LOOP2(c,i) LOOP2(c,i|2)
#define LOOP8(c,i) LOOP4(c,i) LOOP4(c,i|4)
#define LOOP16(c,i) LOOP8(c,i) LOOP8(c,i|8)
#define LOOP32(c,i) LOOP16(c,i) LOOP16(c,i|16)
#define LOOP64(c,i) LOOP32(c,i) LOOP32(c,i|32)

uint64_t add(uint64_t a, uint64_t b) {
	uint64_t c = 0, carry = 0;
	LOOP64(ADD_ROUND, 0);
	return c;
}

uint64_t mul(uint64_t a, uint64_t b) {
	uint64_t c = 0;
	LOOP64(MUL_ROUND, 0);
	return c;
}

int main() {
	uint64_t a = 0xdeadbeef1337;
	uint64_t b = 0xbadf00d31337;
	printf("0x%lx + 0x%lx => 0x%lx\n", a, b, add(a, b));
	printf("0x%lx * 0x%lx => 0x%lx\n", a, b, mul(a, b));
}