got := f.uint64()
		want := x &^ (1<<(64-prec) - 1) // cut off (round to zero) low 64-prec bits
		if got != want {
			t.Errorf("got %#x (%s); want %#x", got, f.Text('p', 0), want)
		}
	}
}

func TestFloatSetInt64(t *testing.T) {
	for _, want := range []int64{
		0,
		1,
		2,
		10,
		100,
		1<<32 - 1,
		1 << 32,
		1<<63 - 1,
	} {
		for i := range [2]int{} {
			if i&1 != 0 {