This is a first try at redundant jump removal (jumps that target the very next instruction). It's too basic in several ways.
- The statement is replaced by a ';' instead of removed.
- If the jump was the only statement in an if, when the if becomes empty, it's not folded.
- Jumps that are last in the 'then' branch of if+else are not visible. This would need either to track multiple last statements, or to have some means to anticipate what the next statement is at every statement. A Control Flow Graph would help a lot.
- When a label is immediately followed by a jump, all jumps to that label should target the destination of that jump if it's in scope. Added to TODO.
- It misses some optimizations when not expanding WHILE and FOR into IF/JUMP.
Moving everything to an earlier stage would help with some of these, especially with ';' and 'if' folding. Unconditionally expanding WHILE and FOR would also help.
