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.

[VarLad]

@maleadt Would you have an example of how to pass the properties flags properly? I'm not sure how this works...
It seems to work differently from the svm flags in the current implementation
Unable to figure out how to use these from the docs:

[maleadt]

AFAIU it behaves like context properties, so you pass a list of properties starting with CL_MEM_ALLOC_FLAGS_INTEL, then a flags bitmask, and terminate with NULL.

julia> using OpenCL, pocl_jll

julia> fun = cl.clGetExtensionFunctionAddressForPlatform(cl.platform(), "clHostMemAllocINTEL")
Ptr{Nothing} @0x0000000135a78178

julia> error = Ref{Int32}();

julia> flags = cl.CL_MEM_ALLOC_WRITE_COMBINED_INTEL;

julia> properties = cl.cl_mem_properties_intel[cl.CL_MEM_ALLOC_FLAGS_INTEL, flags, 0];

julia> buf = ccall(fun, Ptr{Cvoid},
                   (cl.cl_context, Ptr{cl.cl_mem_properties_intel}, Csize_t, cl.cl_uint, Ptr{cl.cl_int}),
                   cl.context(), properties, 1000, 1, error)
Ptr{Nothing} @0x00000001322cee00

julia> @assert error[] == cl.CL_SUCCESS

You can also look at how PoCL implements this:

• properties parsing: https://github.com/pocl/pocl/blob/1990f7556242c0d55750b5bde7262f7ddaebe213/lib/CL/clMemAllocINTEL.c#L40-L58
• contained flag handling: https://github.com/pocl/pocl/blob/1990f7556242c0d55750b5bde7262f7ddaebe213/lib/CL/clMemAllocINTEL.c#L99-L118