hyengine: A Unified Mobile Script Engine with JIT, Optimizations, and GC

hyengine is a lightweight, high‑performance execution engine designed for mobile platforms that unifies the execution of multiple script languages such as WebAssembly, JavaScript, Python and Lua. It consists of a compiler (frontend, middle‑end, backend) and a virtual machine (VM) and provides JIT compilation, register allocation, inline‑cache optimizations, a custom memory allocator (hymalloc) and a multi‑threaded three‑color garbage collector (hygc).

The compiler translates wasm bytecode into ARM64 machine code through a simple direct‑translation pass followed by several optimizer passes (code‑block splitting, register allocation based on access frequency, instruction‑fusion and pattern‑matching). These passes reduce code size from 63 to 32 instructions for a Fibonacci benchmark and cut execution time from 1716 ms to 493 ms, approaching LLVM‑generated code.

For JavaScript, hyengine reuses QuickJS but replaces its reference‑counting GC with hygc, a concurrent three‑color mark‑sweep collector that runs in a background thread and limits pause time to <30 ms. The allocator hymalloc organizes memory into regions, pools and items, achieving up to 4× faster allocation than the system malloc on an M1 Mac.

Additional optimizations include a global‑object inline cache to avoid repeated property look‑ups and fast‑path implementations for frequently used built‑ins such as Array.indexOf. Performance measurements on both macOS (x86/arm64) and Android devices show significant speed‑ups for wasm, JavaScript and mixed workloads.

Future work will focus on extending the compiler with a custom bytecode, adding more optimizer passes, implementing hot‑method JIT in the VM and exploring support for additional languages.