Vulkan: Workaround slow vkCmdCopyImageToBuffer on QCom

[K0bin]

After profiling Mario Galaxy on my Snapdragon 865 phone, I realized that the video thread spends a ridiculous amount of time in vkCmdCopyImageToBuffer.

Turns out the driver allocates a temporary image every single time. After playing around for a bit, I've noticed that it doesn't do that when copying from a linear tiled image. So we can just do that blit ourselves and reuse the image.

EDIT: I should clarify, this is mostly a problem when "Store EFB copies to texture only" is disabled.

[JMC47]

Greatly improves performance on Vulkan. NES VC games run ~100% faster (EFB2RAM ones)

A lot of the 3D games are still slower in Vulkan than OpenGL though. Wind Waker island overview during the opening is full speed on OpenGL and is ~25 FPS on Vulkan (Pixel 3a)

So, while Vulkan performance is better and greatly improved in some cases, it's still not great for most Adrenos.

[iwubcode]

Some questions from me: is there a reason users would prefer Vulkan over OGL? Does it make sense to add additional code complexity for a single platform if it doesn't push Vulkan perf over OGL which users can already use?

[K0bin]

Wind Waker runs at ~45FPS on my phone with both Vulkan and OpenGL. (with the PR)
OpenGL is a lot faster in Mario Galaxy but that's probably because their flushing logic is a lot smarter.

Does it make sense to add additional code complexity for a single platform if it doesn't push Vulkan perf over OGL which users can already use?

I think it's not that much code and it's fairly contained.

[brujo5]

Very nice
Sd860 with v615 driver

[golivax]

In my non scientific tests, I also noticed a massive improvement with Vulkan on a SD855 (stock Galaxy S10). Windwaker and several other games run much better. Indeed, this PR brought Vulkan very close to OpenGL, which is wonderful! I am very curious to see if PR + #11090 will make things even (e.g., in games like Mario Galaxy and Skyward Sword). Tks a lot for your work, @K0bin. I am sure the community will really appreciate it.

[Pokechu22]

Looks good to me. I haven't tested it directly though.

[JMC47]

I can test the latest version to make sure it works, but without other optimizations I won't see the full effect.

Seems to still run, so let's start getting the optimizations merged.