Indeed, you can get them all here - https://gpuopen.com/documentation/amd-isa-documentation/

And that's the ISA that actually executes on the gpu, including instruction encoding and whatnot - not just some IR

Intel can't be too well kept secret either since they develop drivers as opsource.Then there are the reverse engineered mobile GPUs.

Openness is also a no-brainer play to get market share especially as a business-card e.g. if we buy a GPU, it only needs above a certain performance - stock and driver support is all that matters for us in today's market (obviously this is not the case for GPGPU work)