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Fork Focus: AOT App Caching and Static Cache Prebuilds

This fork is focused on adding practical AOT-style app caching workflows to improve runtime behavior and reduce repeated JIT cost.

Why it exists

  • Prebuild executable + dependency cache artifacts before first run.
  • Shift work from runtime JIT to offline cache generation.
  • Improve startup/stutter behavior by increasing cache reuse.

What this adds

  • Static codemap generation + offline cache compilation workflow.
  • Dependency-aware static seeding (main binary + transitive shared libraries).
  • Unified cache naming keys across runtime/server/offline compiler.
  • Runtime cache load/fallback diagnostics.
  • Benchmark framework for baseline vs prebuilt-cache performance comparison (Markdown+JSON output).
  • Validation tooling to confirm cache-enabled behavior remains aligned with JIT.

Impact

  • Better practical performance characteristics from more reusable prebuilt caches.
  • Lower warm-up overhead in repeated app runs.
  • Clearer observability when cache load paths fall back.

Sample benchmark result (heavy canary)

Command used:

./Scripts/dev/run_aot_perf_benchmark_x86_dev.sh \
	--app ./Build-x86dev/Bin/aot_canary \
	--app-name canary-heavy \
	--app-arg 3735928559 \
	--app-arg 600000 \
	--app-arg 2 \
	--no-canary \
	--runs 3 \
	--warmup 0 \
	--timer python \
	--report-dir ./Build-x86dev/AOTBenchmarks/canary-heavy-fast

Measured output:

Workload Baseline median (s) Prebuilt median (s) Delta prebuilt vs baseline
app-canary-heavy 16.337991 15.528765 -4.95%

Interpretation: this heavier synthetic canary profile is tuned to surface prebuilt-cache effects while still finishing in reasonable time. This measurement used the Python timing fallback backend on an x86-host dev setup.

Sample benchmark result (real app: python3)

Command used:

./Scripts/dev/run_aot_perf_benchmark_x86_dev.sh \
	--app /usr/bin/python3 \
	--app-name python3-version \
	--app-arg -V \
	--no-canary \
	--runs 3 \
	--warmup 0 \
	--timer python \
	--report-dir ./Build-x86dev/AOTBenchmarks/python3-version-fast

Measured output:

Workload Baseline median (s) Prebuilt median (s) Delta prebuilt vs baseline
app-python3-version 1.184307 1.185738 +0.12%

Interpretation: this uses a larger real binary than uname, while keeping runtime short for local iteration. It still reflects this specific x86-host dev environment and Python timing backend.

Implementation and day-to-day commands are documented in Scripts/dev/README.md.

Note: x86-host scripts in this fork are a practical development path (used because ARM Linux hardware is not always available). The primary goal is the AOT caching functionality itself.

FEX: Emulate x86 Programs on ARM64

FEX allows you to run x86 applications on ARM64 Linux devices, similar to qemu-user and box64. It offers broad compatibility with both 32-bit and 64-bit binaries, and it can be used alongside Wine/Proton to play Windows games.

It supports forwarding API calls to host system libraries like OpenGL or Vulkan to reduce emulation overhead. An experimental code cache helps minimize in-game stuttering as much as possible. Furthermore, a per-app configuration system allows tweaking performance per game, e.g. by skipping costly memory model emulation. We also provide a user-friendly FEXConfig GUI to explore and change these settings.

Prerequisites

FEX requires ARMv8.0+ hardware. It has been tested with the following Linux distributions, though others are likely to work as well:

  • Arch Linux
  • Fedora Linux
  • openSUSE
  • Ubuntu 22.04/24.04/24.10/25.04

An x86-64 RootFS is required and can be downloaded using our FEXRootFSFetcher tool for many distributions. For other distributions you will need to generate your own RootFS (our wiki page might help).

Quick Start

For Ubuntu 22.04, 24.04, 24.10 and 25.04

Execute the following command in the terminal to install FEX through a PPA.

curl --silent https://raw.githubusercontent.com/FEX-Emu/FEX/main/Scripts/InstallFEX.py | python3

This command will walk you through installing FEX through a PPA, and downloading a RootFS for use with FEX.

For other Distributions

Follow the guide on the official FEX-Emu Wiki here.

Navigating the Source

See the Source Outline for more information.