Support iOS/iPadOS build

[haroel]

Are you considering adding support for iOS builds?

[billywhizz]

hi. yeah. would like to have builds for as many platforms as possible and keep them up to date. iOS, Android, RISCV64. not so concerned about having 32-bit builds. right now, having a lot of pain just getting the builds to work consistently across the current platforms in Github Actions. if you have any suggestions, let me know!

[haroel]

hi. yeah. would like to have builds for as many platforms as possible and keep them up to date. iOS, Android, RISCV64. not so concerned about having 32-bit builds. right now, having a lot of pain just getting the builds to work consistently across the current platforms in Github Actions. if you have any suggestions, let me know!

Hi @billywhizz
Yes，I have been working on V8 compilation recently, mainly focusing on the iOS platform. I plan to adopt V8 version 14.x (and will need to enable v8_enable_drumbrake afterward).
It is indeed quite challenging to make the V8 compilation action support more platforms. However, I noticed that there is a macOS-arm64 build script in the actions(args.mac.arm64.gn), and the records show that the build can be completed successfully.

By referring to your args.mac.arm64.gn (branch: 14.1), I have successfully built the static library for iOS arm64.
Below are my args parameters (which are very similar to those in args.mac.arm64.gn):

      target_os=\"ios\"
      target_cpu=\"arm64\"   
      target_environment=\"device\"
      ios_deployment_target=\"12\"
      compiler_timing=true
      ios_enable_code_signing=false
      treat_warnings_as_errors=false
      use_custom_libcxx=false
      use_rtti=false
      use_sysroot=false
      clang_use_chrome_plugins=false
      dcheck_always_on=false
      enable_rust=false
      is_cfi=false
      is_asan=false
      is_clang=true
      is_component_build=false
      strip_debug_info=true
      v8_deprecation_warnings=false
      v8_enable_temporal_support=false
      v8_imminent_deprecation_warnings=false
      v8_monolithic=true
      v8_use_external_startup_data=false
      v8_enable_gdbjit=false
      v8_enable_i18n_support=false
      v8_enable_test_features=false
      v8_enable_pointer_compression=false
      v8_enable_sandbox=false
      v8_enable_webassembly=false
      v8_enable_drumbrake=false
      is_debug=false
      symbol_level=0

[billywhizz]

thanks @haroel. 🫶

i'll see if i can add that to the existing builds over the weekend. finally have clang on linux/x64 working now. just need to get arm64 on linux working and i should have a good set. i can hopefully set something up to rebuild every time v8 does a stable release.

[haroel]

thanks @haroel. 🫶

i'll see if i can add that to the existing builds over the weekend. finally have clang on linux/x64 working now. just need to get arm64 on linux working and i should have a good set. i can hopefully set something up to rebuild every time v8 does a stable release.

Thank you for your reply Johnston!

The drumbrake code was contributed by the Microsoft technical team: DrumBrake: a Wasm Interpreter for V8

The document indicates that it only supports macOS, Linux, and Windows. By default, v8 does not support enabling drumbrake (interpreter mode webassembly) on iOS.

Regarding this issue, I have communicated with the drumbrake team. They stated that there are no technical obstacles to running drumbrake on iOS, but they do not have the time to verify and test iOS with drumbrake. On the chromium-review.googlesource.com website, I noticed that a developer submitted support for tvOS builds: 6767696: [tvos][wasm interpreter] Enable v8_enable_drumbrake | https://chromium-review.googlesource.com/c/v8/v8/+/6767696 .
Therefore, in theory, enabling v8 drumbrake on iOS should not be a problem.

In the gn settings, I modified BUILD.gn and gni/v8.gni, and successfully built the iOS static library with drumbrake. The changes are as follows:

BUILD.gn

# // delete the assert
if (v8_enable_drumbrake && v8_enable_webassembly) {
  assert(
      is_drumbrake_supported,
      "DrumBrake is only available on x64, arm64 on Windows, Linux and MacOS.")
}

v8.gni

  if (target_os == "ios") {
    if (target_platform == "iphoneos") {
      # iOS executable code pages is in 18.4 SDK which the iOS + Blink targets.
      v8_enable_lite_mode = !use_blink
      v8_enable_lite_mode = true

      # Since v8 has the Wasm interpreter mode with jitless, iOS enables it
      # to use WebAssembly.
      v8_enable_drumbrake = true
      v8_enable_webassembly = true

      # iOS doesn't use Turbofan.
      v8_enable_turbofan = false
      
    } else if (target_platform == "tvos") {
      # tvOS runs in single process mode and is not allowed to use JIT.
      v8_enable_lite_mode = true

      # Since v8 has the Wasm interpreter mode with jitless, tvOS enables it
      # to use WebAssembly.
      v8_enable_drumbrake = true
      v8_enable_webassembly = true

      # tvOS doesn't use Turbofan.
      v8_enable_turbofan = false
    }
  }

The build args :

target_os=\"ios\"
        target_cpu=\"arm64\"
        target_environment=\"device\"
        ios_deployment_target=\"12\"
        compiler_timing=true
        ios_enable_code_signing=false
        treat_warnings_as_errors=false
        use_custom_libcxx=false
        use_rtti=false
        use_sysroot=false
        clang_use_chrome_plugins=false
        dcheck_always_on=false
        enable_rust=false
        is_cfi=false
        is_asan=false
        is_clang=true
        is_component_build=false
        strip_debug_info=true
        v8_deprecation_warnings=false
        v8_enable_temporal_support=false
        v8_imminent_deprecation_warnings=false
        v8_monolithic=true
        v8_use_external_startup_data=false
        v8_enable_gdbjit=false
        v8_enable_i18n_support=false
        v8_enable_test_features=false
        v8_enable_pointer_compression=true  
        v8_enable_sandbox=false   
        v8_enable_webassembly=true
        v8_enable_drumbrake=true

After successfully building the static library of v8 + drumbrake, I spent a lot of time working on the iOS project to get it to launch successfully【enable Increased Memory Limit；add build macro... 】. However, I encountered a crash and haven't yet figured out a good solution for it.

Crash at

create_params.array_buffer_allocator =
         v8::ArrayBuffer::Allocator::NewDefaultAllocator();

// Error log:
[FATAL:partition_address_space.cc(85)] Check failed: false.

[haroel]

I am currently working on a cross-platform v8 + webgl runtime（Android、Windows、iOS、macOS）, developed in C++. It currently runs some webgl games developed with JavaScript, and the next step is to add support for WebAssembly. Before November, I plan to spend some more time experimenting with drumbrake on iOS. If I can't resolve the issues, I will switch to using wasmi (a pure interpreter WebAssembly runtime developed in Rust).