The compiler is LLVM

https://github.com/llvm/llvm-project/tree/main/llvm/lib/Targ...

It's all there. For the driver/runtime everything is also open and upstreamed into the Linux kernel (register map and pcie bar and etc). The packet protocol isn't well-documented but documented enough that tinygrad managed to build their own driver from scratch.

Intel still has to publish several additional manuals, to cover Xe in Meteor Lake, Xe in Arrow Lake H, Xe 2 in Lunar Lake and Xe 2 in discrete GPUs, and then Xe 3 in Panther Lake, to bring their documentation up to date.

You can extract most of the GPU information from the open-source Linux drivers and LLVM compiling back-end, but this is a poor substitute for actual GPU ISA documentation.

edit: they are scary huge.