// Look through all extensions
func signExtNto64(x []int, j8 int8, j16 int16, j32 int32) int {
	if len(x) < 22 {
		return 0
	}
	if j8 >= 0 && j8 < 22 {
		return x[j8] // ERROR "Proved IsInBounds$"
	}
	if j16 >= 0 && j16 < 22 {
		return x[j16] // ERROR "Proved IsInBounds$"
	}
	if j32 >= 0 && j32 < 22 {
		return x[j32] // ERROR "Proved IsInBounds$"
	}