MULWB	R1, R2, R3           // a20123e1
	MULWT	R1, R2, R3           // e20123e1

// REV
	REV	R1, R2               // 312fbfe6
	REV16	R1, R2               // b12fbfe6
	REVSH	R1, R2               // b12fffe6
	RBIT	R1, R2               // 312fffe6

// XTAB/XTAH/XTABU/XTAHU
	XTAB	R2@>0, R8            // 7280a8e6
	XTAB	R2@>8, R8            // 7284a8e6
	XTAB	R2@>16, R8           // 7288a8e6

	{"fofofofofoofofoffofoobarfoo", "foobars", -1},
	{"foofyfoobarfoobar", "y", 4},
	{"oooooooooooooooooooooo", "r", -1},
	{"oxoxoxoxoxoxoxoxoxoxoxoy", "oy", 22},
	{"oxoxoxoxoxoxoxoxoxoxoxox", "oy", -1},
	// test fallback to Rabin-Karp.
	{"000000000000000000000000000000000000000000000000000000000000000000000001", "0000000000000000000000000000000000000000000000000000000000000000001", 5},
}

var lastIndexTests = []BinOpTest{
	{"", "", 0},

		}
		if s[i+1] == c1 && Equal(s[i:i+n], sep) {
			return i
		}
		i++
		fails++
		if fails >= 4+i>>4 && i < t {
			// Give up on IndexByte, it isn't skipping ahead
			// far enough to be better than Rabin-Karp.
			// Experiments (using IndexPeriodic) suggest
			// the cutover is about 16 byte skips.
			// TODO: if large prefixes of sep are matching
			// we should cutover at even larger average skips,