ICD JLL does not include USM functions

[VarLad]

could not load symbol "clHostMemAllocINTEL":

~/.julia/artifacts/c99d19d2f6dd75af3e997c4ecc4ac85e410cb7a7/lib/libOpenCL.so: undefined symbol: clHostMemAllocINTEL

To reproduce:

using OpenCL
error = Ref{Int32}()
al = cl.clHostMemAllocINTEL(cl.context(), C_NULL, 10000, 1, error)

Could this be an issue in using the function itself (wrong parameters or something)? 🤔

[maleadt]

I think this is intended. The ICD we use only provides entry-points for functions from the spec, and for extensions one needs to use clGetExtensionFunctionAddressForPlatform to fetch the entrypoint address:

julia> using OpenCL, pocl_jll

julia> ptr = cl.clGetExtensionFunctionAddressForPlatform(cl.platform(), "clHostMemAllocINTEL")
Ptr{Nothing} @0x000000013131f000

julia> error = Ref{Int32}()
Base.RefValue{Int32}(219365504)

julia> ccall(ptr, Ptr{Cvoid}, (cl.cl_context, Ptr{cl.cl_mem_properties_intel}, Csize_t, cl.cl_uint, Ptr{cl.cl_int}), cl.context(), C_NULL, 1000, 1, error)
Ptr{Nothing} @0x0000000121016e00

julia> error[]
0

It's a bit annoying that we can't re-use the existing Clang.jl-generated headers for this, although for the handful of USM functions you need it's probably fine duplicating those ccalls.