src/new32v3.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

#include <stdint.h>

static const unsigned int divtab[730] = {
	[1] = 0xffff + 1l,
	[3] = 0x5555 + 1l,
	[9] = 0x1c71 + 1l,
	[27] = 0x097b + 1l,
	[81] = 0x0329 + 1l,
	[243] = 0x010d + 1l,
	[729] = 0x0059 + 1l
};

#define FASTDIV(n, d) (((n) * divtab[d]) >> 16)

int new32v3(int i, int x, int y)
{
	int A;
	A = i + x * y;
	return A - 3 * y * (FASTDIV(A, 3 * y) - FASTDIV(i, 3 * y));
}