// ADDV C_SCON, [r1], r2
	ADDV	$0x321, R4			// ADDV	$801, R4			// 8484cc02
	ADDV	$0x321, R5, R4			// ADDV	$801, R5, R4			// a484cc02
	ADDV	$0xfffffffffffffc21, R4		// ADDV	$-991, R4			// 8484f002
	ADDV	$0xfffffffffffffc21, R5, R4	// ADDV	$-991, R5, R4			// a484f002

	// AND C_SCON, [r1], r2
	AND	$0x321, R4			// AND	$801, R4			// 84844c03

	const haveFastIndex = bytealg.MaxBruteForce > 0
	switch {
	case 0 <= r && r < utf8.RuneSelf:
		return IndexByte(s, byte(r))
	case r == utf8.RuneError:
		for i := 0; i < len(s); {
			r1, n := utf8.DecodeRune(s[i:])
			if r1 == utf8.RuneError {
				return i
			}
			i += n
		}
		return -1
	case !utf8.ValidRune(r):
		return -1
	default:
		// Search for rune r using the last byte of its UTF-8 encoded form.