Only emit jump table if contract has indirect jump

[laurenthuberdeau]

Context

On the 20425 contracts executed at least 5 times between block 15M to ~19M, around 9365 have only direct jumps. Other contracts have a mix of direct and indirect jumps. For the contracts with only direct jumps, the jump table occupies around 5% of the total compiled code size (see table below showing the jump table size over the total code size), which can be removed since it will never be used.

 avg_jt | p10_jt | p50_jt | p90_jt | p99_jt 
--------+--------+--------+--------+--------
    4.9 |    3.8 |    4.5 |    5.6 |    7.4
(1 row)

[Copilot]

Pull Request Overview

This PR optimizes compiled contract size by only generating jump tables when contracts contain indirect jumps. Based on analysis of ~20k contracts, approximately 46% contain only direct jumps, and for those contracts the jump table represents ~5% of compiled code size that can be eliminated.

• Changed jump table label from required to optional using std::optional<asmjit::Label>
• Added lazy initialization of jump table label only when first indirect jump is encountered
• Wrapped jump table generation code with conditional check to skip emission when no indirect jumps exist

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
category/vm/compiler/ir/x86/emitter.hpp	Changed jump_table_label_ member from asmjit::Label to std::optionalasmjit::Label
category/vm/compiler/ir/x86/emitter.cpp	Updated initialization, added conditional jump table generation, and lazy label creation

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