The first instruction of every block is kept as the label for that block.

This means that even if it is useless it will not be removed.

if (a === 0) {
    1 + 1
}

The content of the if branch gets generate to be this

 9: 14 00 08                 MoveConst C0, r2
12: 10 01                    LoadInt 1
14: 80 08                    Add r2, acc

And then optimized to

 9: 14 00 08                 MoveConst C0, r2 

where the first instruction is kept because it "holds" the label.

This could potentially also prevent detecting empty branches later on.