GTA V native iOS port:
how it was built

Why native

The first attempt used Madeira: FEX x86 emulation, Wine ARM64EC, and DXMT on an iPhone 13 Pro. It ran after fixes for missing d3dx11, clip-distance geometry-shader asserts, save paths, streamed-file corruption from the RageSec bonder, and 10-second audio memset freezes.

Performance remained at 10–25 FPS. TSO emulation was CPU-bound on two performance cores, while memory stayed at the 4 GB limit. That led to a native build.

Native arm64 base

The macOS build came first. The PC game stayed intact, including RSG_PC, the D3D11 renderer, and PC menus. The platform underneath changed.

• Compiler and ABI: MSVC / LLP64 became clang / Itanium / LP64. Unity translation units were extracted from the .sln into a Ninja build. Source edits are replayable patch scripts, with 55 batches recorded in these development notes.
• CPU: SSE support remains through sse2neon. Moving from the x86 to the arm64 memory model required -fms-volatile, real dmb barriers, and full fences after interlocked operations. Without them, the job scheduler lost wake-ups and froze.
• Data: Orbis clang struct padding lets PC resources load unchanged. RPF archives are decrypted offline because TransformIT is a binary-only x64 library.
• Win32 compatibility: libgtacompat reimplements approximately 500 imports. These cover kernel32 waits, threads mapped to quality-of-service classes, virtual memory with 16 KB pages, files, and thread-local storage; a 16-bit wchar C runtime; a user32 window and message queue; DirectInput / XInput through GameController; CoreAudio; and crash / hang reports.
• Graphics: DXMT runs natively with an LLVM 15 shader converter. Its window-system integration was replaced with a custom view.
• Stubbed integrations: Bink, NVIDIA / AMD libraries, Steam, and telemetry were stubbed out.

The iOS target

• The same source tree initially targeted iOS 18+ on arm64. A UIKit backend replaces Cocoa, using a Playback audio session so the silent switch does not mute the game, and Files app access to the game folder.
• DXMT on iOS: UIKit replaces AppKit; macOS-only Metal APIs are removed; shader caches live in Library/Caches; Metal shaders target iphoneos; and LLVM is cross-built for iOS.
• An Xcode stub app uses a free signing profile with the increased-memory-limit entitlement. Deployment, execution, and log collection use scripts around devicectl.

The iOS 18 target describes the original development stage. Later release notes document iOS 16.3+ support. See the 17 October update.

Getting a correct frame on A15

The Mac rendered correctly before the phone did. Three issues needed separate fixes.

1. Triangle strips: degenerate strips with a vertex behind the camera produced streaks on A15. The CPU now rewrites them as indexed triangle lists.
2. Render targets: NaN and infinity writes to R11G11B10 / RGB9E5 targets are filtered and clamped.
3. Shader conversion: DXMT’s LLVM, through Xcode’s libc++, bound to the compatibility layer’s 16-bit wmemchr. InstCombine silently dropped vector lanes, leaving approximately 60% of converted shaders incorrect, including black SSAO and broken water. Retagging the iOS dynamic library as macOS and loading it on the Mac exposed the issue. The fix was a private 32-bit wmemchr inside DXMT.

Memory: 3.9 GB to about 1.9 GB

• Texture conversion: A15 cannot sample BC textures. Runtime BC → ETC2 / EAC transcoding initially kept the same block sizes and saved about 1 GB. Phone archives were then converted offline, removing a CPU cost of 0.5–7 seconds per 10 seconds of play.
• GPU capture: an apparent 800 MB leak came from Apple’s GPU capture layer, loaded by an Info.plist key.
• Low-memory profile: an automatic profile applies to devices with 4.5 GB of RAM or less.
• Shaders: DXMT shader intermediate representation is freed after compilation. DXBC stays compressed, saving about 250 MB.
• Heap reclamation: freed heap blocks return to the operating system with madvise.

Recorded result at this stage1.91 GB peak during play

Controls and user experience

• Touch input: controls act as a virtual XInput gamepad. The game reports contexts such as on foot, vehicle, menu, weapon wheel, and phone. Each has an editable layout accessible from the pause menu. A physical controller hides the overlay.
• Settings: added MetalFX, an FPS counter, Shadows Off, extra Advanced Graphics rows, Draw Distance, first-person field of view and aim field of view, and Temporal AA using a custom resolve shader in DXMT.
• Device resets: settings requiring a reset did not apply until the compatibility layer’s SetWindowPos sent WM_WINDOWPOSCHANGED.
• Launcher: a configurator inspired by the Rockstar launcher runs before the game starts.

Performance and power

• Scheduling: thread quality-of-service mapping directs the render and main threads toward the two performance cores.
• Frame delivery: unlocked 120 Hz, a 24 FPS limiter step, and Metal-paced presents. The display link stays at the top rate to keep iOS from parking the performance cores.
• Diagnostics: the overlay shows thermal state, CPU power in watts, and active cores.
• iPhone 13 Pro observation: 60 FPS while the thermal state was “fair.” Heat, rather than GPU capacity, was the limiting factor in that observation.

Install size: 29.5 GB to 21.6 GB

• Resource compression: the streamer detects zstd per resource. Recompressed resources are approximately 80% of their deflate size and decode at similar or higher speed.
• Audio: an Opus decoder was added to the engine. The phone uses a dedicated low-bitrate Opus set, which also replaces remaining ADPCM audio.
• Data preparation: one script rebuilds the phone data through decryption, ETC conversion, and zstd compression, with verification at each step.

Where it is now

• iPhone 13 Pro: approximately 30 FPS and 2.3 GB of memory in the game world in the current observations described by these notes.
• iPad: support is built and verified working.
• Minimum hardware described here: an A12-family chip (A12, A12X, or A12Z) and 4 GB of RAM.

A12 support is experimental in the 24 October evening test build and the 25 October release. Start with the lowest preset on 4 GB devices. Review the release notes for the build you install.