dynarmic VS MoltenVK

They're probably referring to dynarmic: https://github.com/merryhime/dynarmic

As an HLE, touchHLE is radically different from a low-level emulator (LLE) like QEMU. The only code the emulated CPU executes is the app binary and a handful of libraries; touchHLE takes the place of iPhone OS and provides its own implementations of the system frameworks (Foundation, UIKit, OpenGL ES, OpenAL, etc).

https://github.com/merryhime/dynarmic/pull/697 - Dynarmic implementing Arm backend support. Dynarmic is a dynamic recompiler for ARM.

I did some work on Dynarmic, so there's my bias I guess. But I def believe Dynarmic would emit better context-aware assembly than a CIL->Native jitteror the JVM would emit. Dynarmic takes advantage of instruction sets like BMI2 and AVX{2,512} and uses a pretty darn concise intermediate representation to the original ARM assembly to emit efficient x86 while a C# JIT probably still only emits baseline x86-64 and struggles with efficient vectorization of things like Arm's NEON instructions. Can't even imagine a C# or Java VM trying to automatically emit optimal assembly for an FMADD including handling NaN propagation or detecting that FMINNM can be very quickly emulated with a single vrangep{s,d} x86 instruction.

For emulators, it's currently used in dynarmic(Yuzu's ARM-to-x86 recompiler backend) for the fast emulation of ARM's NEON instruction set.

https://github.com/KhronosGroup/MoltenVK

Translating between rendering APIs is not really the problem. The GPU design is more different than the API is.

Khronos maintains MoltenVk though, which is "official" as it gets: https://github.com/KhronosGroup/MoltenVK

...technically, Vulkan on Windows is also only supported via 3rd-parties (the GPU vendors), Microsoft doesn't support Vulkan either ;)

MoltenVK implements large parts of Vulkan on top of Metal for Apple systems. It isn't full Vulkan but it makes porting Vulkan games to OS X easier.

That's cool. Maybe I haven't thought enough about this. Let me check it out. FWIW it's this PR that you are referring to I think: https://github.com/KhronosGroup/MoltenVK/pull/1815/

For Metal specifically, they could adopt and contribute to Vulkan and get access to a lot more software. Right now you need to use a compatibility layer, and surely Apple could just support both APIs natively with much lower overhead. But they don't, because it nudges developers to stick to the Apple ecosystem instead of being able to support multiple platforms.

At the moment the most promising thing is MoltenVK (DX12 -> DXVK -> Vulkan -> MoltenVK -> Metal), but the development is not that quick mainly because there aren't tons of developer that works at the same time on the project. It's not actually a Metal related problem at the moment (they have a road map of things that they can be achieved with Metal 3 like Mesh shader and Geometry shader).

What you asked is already existed for at least 8 years. Yeah EIGHT years. It's called "MoltenVK". So far it's the only implementation of Vulkan for macOS. Basically it's a wrapper that runs on top of Metal API.