In theory you could do parallel scan tricks to implement primitive restart at full speed, but obviously it's going to cost you and it complicates the index fetc

In theory you could do parallel scan tricks to implement primitive restart at full speed, but obviously it's going to cost you and it complicates the index fetch immensely since it effectively ends up being split into two parts. Most likely, Apple simply doesn't build GPUs big enough to run into that problem, but it makes you wonder what they're doing on their hardware with AMD GPUs.