Function optimize 

pub fn optimize(ops: &mut Vec<PcodeOp>)

Peephole-optimize a P-code op sequence:

• Fold small constant integer/logical expressions.
• Remove identity Subpiece { lsb: 0 } where input.size == out.size.
• Forward-substitute Copy chains (A=B, C=A → C=B) when the intermediate is a unique varnode used only once after its definition.