Brian Degenhardt
6f3ee20df9
The Android shader tree carried capability-gated blocks that bin was missing,
even though the shared C++ backends emit every gating macro on all platforms
(GSDeviceOGL.cpp:2006-2010, GSDeviceVK.cpp:4769 — GPU_PROFILE_MALI,
HAS_ARM/EXT_SHADER_FRAMEBUFFER_FETCH, HAS_ARM_DEPTH_FETCH, HAS_CLIP_CONTROL,
DISABLE_DUAL_SOURCE). bin was simply the stale copy; the desktop GL backend is
already wired to consume the mobile shader structure (see the GPU_PROFILE_MALI
reference at GSDeviceOGL.cpp:1067). Collapse the two to one superset so drift
becomes impossible.
- opengl/{convert,interlace,present,tfx_fs,tfx_vgs}.glsl, vulkan/present.glsl:
adopt the Android version verbatim. Every difference is either macro-gated
(desktop path preserved in the #else — e.g. the tfx_vgs z-remap lives under
#else of #if HAS_CLIP_CONTROL, dead on desktop which has ARB_clip_control) or
a GLES-strict float/cast tweak that is behaviorally identical on desktop.
- vulkan/tfx.glsl: hand-merged. Union in the additive tiler blocks (Mali
EQUAL_WZ z-nudge on both the direct and VS_EXPAND paths, the
VS_PROVOKING_VERTEX_LAST and !VS_IIP provoking-vertex handling) and drop
layout(depth_less) per its float32-rounding correctness rationale, while
KEEPING bin's newer two-flag ROV implementation (rov_discard_color/depth) —
that path is dead on mobile since ROV is now off on all tilers. Preprocessor
structure verified balanced and identical to Android's directive counts.
dx11/tfx.fx is Windows-only (never compiled on mobile) and the two remaining
vulkan files differ only in trailing whitespace, so they stay as-is; the mobile
copies get removed and generated from bin in the build-plumbing step.
ARMSX2 — Native ARM64 JIT Fork of PCSX2
ARMSX2 is a free and open-source PlayStation 2 (PS2) emulator based on PCSX2. Its purpose is to emulate the PS2's hardware, using a combination of MIPS CPU Interpreters, Recompilers and a Virtual Machine which manages hardware states and PS2 system memory. This allows you to play PS2 games on your phone, PC, or gaming handheld, with many additional features and benefits.
Thank You
The ARMSX2 team is eternally indebted to the PCSX2 project it is based on. We are so fortunate to build on their 20 years of hardcore development.
About This Fork
The upstream PCSX2 project ships an ARM64 interpreter build for ARM, but its high-performance JIT recompilers (EE, IOP, VU0, VU1, and vtlb fast memory) are x86-64 only.
This fork exists to close that gap. The goal is to preserve the correctness features of 20 years of PCSX2 development, while generating the fastest native ARM performance possible.
Current status:
- ✅ EE (Emotion Engine) recompiler — integer, float, MMI, COP0/COP1/COP2, branches, load/store
- ✅ IOP (I/O Processor / R3000A) recompiler — full integer, load/store, branches, coprocessors
- ✅ VU (Vector Unit) recompiler — microVU skeleton + Upper FMAC vector ISA complete; Lower ISA and runtime complete
- ✅ vtlb fast memory
- ✅ Native ARM64 binary builds and boots the PS2 BIOS
- ✅ 2D games are already playable
- ✅ 3D games run
Why LLMs / AI Were Used
A word on methodology:
The x86-64 JIT code in upstream ARMSX2 is already proven correct — it has run thousands of PS2 titles for years. The challenge in this port is not emulator design or JIT theory; it is mechanical translation of a large, well-understood x86-64 assembly codebase into equivalent ARM64 assembly (via VIXL) while preserving the exact same register-allocation contracts, block lifecycle, and recompiler semantics.
Large language models (LLMs) were used as an accelerant for this translation work — pattern-matching x86 JIT boilerplate to ARM64 equivalents, scaffolding emit routines, and keeping the porting velocity high. The JIT logic (block compiler, dispatcher, analysis passes, flag pipelines, clamping rules, Tri-Ace hacks, etc.) is taken directly from the upstream x86 implementation and validated against it. Nothing was hallucinated from scratch.
In other words: the hard engineering was done by the PCSX2 team over two decades. The hard typing — translating ~50k lines of x86 emitter code into ARM64 — is what AI helped compress.
System Requirements
ARMSX2 targets ARM64 across desktop (macOS, Windows, Linux) and mobile (Android, iOS/iPadOS), all from the single shared core. Our setup documentation page contains additional details on software and hardware requirements.
Please note that a BIOS dump from a legitimately-owned PS2 console is required to use the emulator. For more information, visit this page.
Building
Check out our github actions for the latest build recipe