The pil optimizer can evaluated operations on literals like 1 + 3 -> 4, but it cannot make use of associativity and commutativity. So it does not optimize x + 1 + 3 to x + 4, because it is parsed as (x + 1) + 3.

We should implement the following rules (Li is a literal, X is any expression) - in post-visit-order:

• (X + L1) + L2 -> X + (L1 + L2)
• (L1 + X) + L2 -> X + (L1 + L2)
• (L1 + X) + Y -> (X + Y) + L1 (this is needed to simplify e.g. ((X + 3) + Y) + 9)
• (X + L1) + Y -> (X + Y) + L1
• ...