for i := range A {
		x := A[i]
		y := B[i]
		X := T.Bswap64(x) // ERROR "intrinsic substitution for Bswap64"
		Y := T.Bswap64(y) // ERROR "intrinsic substitution for Bswap64"
		if y != X {
			logf("Bswap64(0x%08x) expected 0x%08x but got 0x%08x\n", x, y, X)
		}
		if x != Y {
			logf("Bswap64(0x%08x) expected 0x%08x but got 0x%08x\n", y, x, Y)
		}

		x32 := uint32(X)
		y32 := uint32(Y >> 32)

		if got := sys.TrailingZeros32(x); got != i {
			t.Errorf("TrailingZeros32(%d)=%d, want %d", x, got, i)
		}
	}
}

func TestBswap64(t *testing.T) {
	x := uint64(0x1122334455667788)
	y := sys.Bswap64(x)
	if y != 0x8877665544332211 {
		t.Errorf("Bswap(%x)=%x, want 0x8877665544332211", x, y)
	}
}
func TestBswap32(t *testing.T) {
	x := uint32(0x11223344)
	y := sys.Bswap32(x)
	if y != 0x44332211 {

// Len8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
func Len8(x uint8) int {
	return int(len8tab[x])
}

// Bswap64 returns its input with byte order reversed
// 0x0102030405060708 -> 0x0807060504030201
func Bswap64(x uint64) uint64 {
	c8 := uint64(0x00ff00ff00ff00ff)
	a := x >> 8 & c8
	b := (x & c8) << 8
	x = a | b
	c16 := uint64(0x0000ffff0000ffff)
	a = x >> 16 & c16