OpenCL Extension Loader

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This repository contains an extension loader library for OpenCL extension APIs.

The extension loader library provides function definitions for all known OpenCL extension APIs and code to query the extension APIs, allowing them to be called just like core OpenCL APIs.

How to Build the OpenCL Extension Loader

The OpenCL Extension Loader uses CMake to generate build files. It is regularly used and tested on Windows and Linux.

The OpenCL Extension Loader requires the following external dependencies: OpenCL headers and an OpenCL library to link with. These dependencies can be provided via several different methods:

1. Via CMake's find_package(OpenCL). For many operating systems, if OpenCL packages or vendor-specific SDKs are installed in standard locations, they will be found automatically. Updated CMake packages may also be provided by the Khronos OpenCL-SDK.

2. Specified manually via the CMake variables OpenCL_INCLUDE_DIRS and OpenCL_LIBRARIES. For these variables, please note that OpenCL_INCLUDE_DIRS should be the full path to the OpenCL headers (the directory containing the CL directory), and that OpenCL_LIBRARIES should be the full filepath to the OpenCL library (e.g. OpenCL.dll or libOpenCL.so).

The OpenCL Extension Loader may also be used as a CMake sub-project, in which case it will inherit the CMake variables OpenCL_INCLUDE_DIRS and OpenCL_LIBRARIES if set, and will find_package(OpenCL) otherwise.

How to Use the OpenCL Extension Loader

After building the OpenCL Extension Loader, simply link with it as you would link to the standard OpenCL libraries. This will satisfy build dependencies for OpenCL extension APIs, allowing them to be called just like core OpenCL APIs.

For example usage, please see SimpleOpenCLSamples.

How to Generate Support for New Extensions

The OpenCL Extension Loader is generated from API definitions in the OpenCL XML File and several Python Mako Templates. To add support for many new extensions, simply run the gen_openclext.py script in the scripts directory. To simplify generation, there is also a CMake target extension_loader_generate, which will invoke the script.

After generation, examine the generated files to ensure everything looks correct, then copy the generated files to the OpenCL Extension Loader source directories. This can be done manually, or via the CMake target extension_loader_copy.

In some cases, the scripts themselves may need to be modified. This typically happens when an extension adds a new type. When an extension adds a new type:

• The OpenCL Extension Loader template file openclext.cpp.mako may need to add a function to get the OpenCL Extension Loader dispatch table from an object of the new type.
• The OpenCL Extension Loader template file may also need to be modified if new extension functions are atypical and the OpenCL Extension Loader dispatch table should not be queried from the first function parameter.
• The OpenCL Extension Loader test generation template file may need to be updated to add default values for the new type.

The OpenCL Extension Loader is most commonly used with the upstream OpenCL XML File, but it can also be used with a fork of the upstream OpenCL XML File, say to generate functions for a private or as-yet unreleased extension.

CMake Variables

The following CMake variables are supported. To specify one of these variables via the command line generator, use the CMake syntax -D<option name>=<value>. See your CMake documentation for more details.

Variable	Type	Description
OPENCL_EXTENSION_LOADER_FORCE_STATIC_LIB	BOOL	Unconditionally Build a Static OpenCL Extension Loader. A static library can simplify building and distribution. Default: TRUE
OPENCL_EXTENSION_LOADER_SINGLE_PLATFORM_ONLY	BOOL	Only Support Extensions from a Single OpenCL Platform. This may improve performance by simplifying dispatch table lookups. Default: FALSE
OPENCL_EXTENSION_LOADER_INSTALL	BOOL	Generate a CMake Installation Target for the OpenCL Extension Loader. Default: FALSE
OPENCL_EXTENSION_LOADER_INCLUDE_GL	BOOL	Include OpenGL Interop Extension APIs. Requires OpenGL Headers. Default: TRUE
OPENCL_EXTENSION_LOADER_INCLUDE_EGL	BOOL	Include EGL Interop Extension APIs. Requires EGL Headers. Default: TRUE
OPENCL_EXTENSION_LOADER_INCLUDE_DX9	BOOL	Include DirectX 9 Interop Extension APIs. Requires DirectX 9 Headers. Default: FALSE
OPENCL_EXTENSION_LOADER_INCLUDE_D3D10	BOOL	Include Direct3D 10 Interop Extension APIs. Requires DirectX 10 Headers. Default: FALSE
OPENCL_EXTENSION_LOADER_INCLUDE_D3D11	BOOL	Include Direct3D 11 Interop Extension APIs. Required DirectX 11 Headers. Default: FALSE
OPENCL_EXTENSION_LOADER_INCLUDE_VA_API	BOOL	Include VA_API Interop Extension APIs. Requires support for VA_API Headers. Default: FALSE
OPENCL_EXTENSION_LOADER_XML_PATH	FILEPATH	Full path to an XML file (e.g. cl.xml) for OpenCL Extension Loader generation. Default: None.

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