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add a global variable pointer sample
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‎samples/99_globalvar/CMakeLists.txt‎

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# Copyright (c) 2025 Ben Ashbaugh
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#
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# SPDX-License-Identifier: MIT
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add_opencl_sample(
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TEST
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NUMBER 99
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TARGET globalvar
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VERSION 210
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SOURCES main.cpp)

‎samples/99_globalvar/main.cpp‎

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/*
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// Copyright (c) 2019-2025 Ben Ashbaugh
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//
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// SPDX-License-Identifier: MIT
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*/
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#include <popl/popl.hpp>
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#include <CL/opencl.hpp>
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#include <fstream>
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#include <string>
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#include "util.hpp"
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static std::vector<cl_uchar> readSPIRVFromFile(
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const std::string& filename )
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{
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std::ifstream is(filename, std::ios::binary);
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std::vector<cl_uchar> ret;
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if (!is.good()) {
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printf("Couldn't open file '%s'!\n", filename.c_str());
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return ret;
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}
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size_t filesize = 0;
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is.seekg(0, std::ios::end);
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filesize = (size_t)is.tellg();
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is.seekg(0, std::ios::beg);
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ret.reserve(filesize);
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ret.insert(
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ret.begin(),
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std::istreambuf_iterator<char>(is),
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std::istreambuf_iterator<char>() );
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return ret;
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}
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static cl::Program createProgramWithIL(
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const cl::Context& context,
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const std::vector<cl_uchar>& il )
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{
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cl_program program = nullptr;
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// Use the core clCreateProgramWithIL if a device supports OpenCL 2.1 or
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// newer and SPIR-V.
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bool useCore = false;
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// Use the extension clCreateProgramWithILKHR if a device supports
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// cl_khr_il_program.
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bool useExtension = false;
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std::vector<cl::Device> devices = context.getInfo<CL_CONTEXT_DEVICES>();
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for (auto device : devices) {
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#ifdef CL_VERSION_2_1
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// Note: This could look for "SPIR-V" in CL_DEVICE_IL_VERSION.
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if (getDeviceOpenCLVersion(device) >= CL_MAKE_VERSION(2, 1, 0) &&
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!device.getInfo<CL_DEVICE_IL_VERSION>().empty()) {
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useCore = true;
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}
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#endif
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if (checkDeviceForExtension(device, "cl_khr_il_program")) {
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useExtension = true;
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}
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}
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#ifdef CL_VERSION_2_1
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if (useCore) {
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program = clCreateProgramWithIL(
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context(),
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il.data(),
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il.size(),
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nullptr);
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}
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else
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#endif
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if (useExtension) {
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cl::Platform platform{ devices[0].getInfo<CL_DEVICE_PLATFORM>() };
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auto clCreateProgramWithILKHR_ = (clCreateProgramWithILKHR_fn)
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clGetExtensionFunctionAddressForPlatform(
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platform(),
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"clCreateProgramWithILKHR");
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if (clCreateProgramWithILKHR_) {
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program = clCreateProgramWithILKHR_(
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context(),
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il.data(),
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il.size(),
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nullptr);
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}
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}
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return cl::Program{ program };
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}
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int main(
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int argc,
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char** argv )
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{
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int platformIndex = 0;
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int deviceIndex = 0;
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std::string fileName(sizeof(void*) == 8 ? "sample_kernel64.spv" : "sample_kernel32.spv");
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std::string buildOptions;
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{
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popl::OptionParser op("Supported Options");
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op.add<popl::Value<int>>("p", "platform", "Platform Index", platformIndex, &platformIndex);
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op.add<popl::Value<int>>("d", "device", "Device Index", deviceIndex, &deviceIndex);
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op.add<popl::Value<std::string>>("", "file", "Kernel File Name", fileName, &fileName);
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op.add<popl::Value<std::string>>("", "options", "Program Build Options", buildOptions, &buildOptions);
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bool printUsage = false;
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try {
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op.parse(argc, argv);
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} catch (std::exception& e) {
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fprintf(stderr, "Error: %s\n\n", e.what());
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printUsage = true;
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}
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if (printUsage || !op.unknown_options().empty() || !op.non_option_args().empty()) {
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fprintf(stderr,
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"Usage: globalvar [options]\n"
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"%s", op.help().c_str());
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return -1;
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}
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}
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std::vector<cl::Platform> platforms;
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cl::Platform::get(&platforms);
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cl::Platform& platform = platforms[platformIndex];
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printf("Running on platform: %s\n",
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platform.getInfo<CL_PLATFORM_NAME>().c_str() );
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std::vector<cl::Device> devices;
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platform.getDevices(CL_DEVICE_TYPE_ALL, &devices);
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cl::Device& device = devices[deviceIndex];
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printf("Running on device: %s\n",
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device.getInfo<CL_DEVICE_NAME>().c_str() );
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printf("CL_DEVICE_ADDRESS_BITS is %d for this device.\n",
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device.getInfo<CL_DEVICE_ADDRESS_BITS>() );
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// Check for SPIR-V support. If the device supports OpenCL 2.1 or newer
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// we can use the core clCreateProgramWithIL API. Otherwise, if the device
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// the cl_khr_il_program extension we can use the clCreateProgramWithILKHR
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// extension API. If neither is supported then we cannot run this sample.
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#ifdef CL_VERSION_2_1
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// Note: This could look for "SPIR-V" in CL_DEVICE_IL_VERSION.
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if (getDeviceOpenCLVersion(device) >= CL_MAKE_VERSION(2, 1, 0) &&
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!device.getInfo<CL_DEVICE_IL_VERSION>().empty()) {
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printf("Device supports OpenCL 2.1 or newer, using clCreateProgramWithIL.\n");
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} else
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#endif
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if (checkDeviceForExtension(device, "cl_khr_il_program")) {
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printf("Device supports cl_khr_il_program, using clCreateProgramWithILKHR.\n");
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} else {
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printf("Device does not support SPIR-V, exiting.\n");
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return -1;
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}
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cl::Context context{device};
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cl::CommandQueue commandQueue{context, device};
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printf("Reading SPIR-V from file: %s\n", fileName.c_str());
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std::vector<cl_uchar> spirv = readSPIRVFromFile(fileName);
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printf("Building program with build options: %s\n",
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buildOptions.empty() ? "(none)" : buildOptions.c_str() );
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cl::Program program = createProgramWithIL( context, spirv );
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program.build(buildOptions.c_str());
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for( auto& device : program.getInfo<CL_PROGRAM_DEVICES>() )
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{
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printf("Program build log for device %s:\n",
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device.getInfo<CL_DEVICE_NAME>().c_str() );
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printf("%s\n",
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program.getBuildInfo<CL_PROGRAM_BUILD_LOG>(device).c_str() );
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}
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typedef cl_int CL_API_CALL
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clGetDeviceGlobalVariablePointerINTEL_t(
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cl_device_id device,
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cl_program program,
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const char *globalVariableName,
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size_t *globalVariableSizeRet,
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void **globalVariablePointerRet);
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typedef clGetDeviceGlobalVariablePointerINTEL_t *
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clGetDeviceGlobalVariablePointerINTEL_fn;
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typedef cl_int CL_API_CALL
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clGetMemAllocInfoINTEL_t(
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cl_context context,
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const void* ptr,
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cl_mem_info_intel param_name,
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size_t param_value_size,
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void* param_value,
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size_t* param_value_size_ret);
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typedef clGetMemAllocInfoINTEL_t *
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clGetMemAllocInfoINTEL_fn ;
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auto clGetDeviceGlobalVariablePointerINTEL = (clGetDeviceGlobalVariablePointerINTEL_fn)
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clGetExtensionFunctionAddressForPlatform(platform(), "clGetDeviceGlobalVariablePointerINTEL");
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auto clGetMemAllocInfoINTEL = (clGetMemAllocInfoINTEL_fn)
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clGetExtensionFunctionAddressForPlatform(platform(), "clGetMemAllocInfoINTEL");
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if (clGetDeviceGlobalVariablePointerINTEL == nullptr) {
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printf("Couldn't get function pointer for clGetDeviceGlobalVariablePointerINTEL!\n");
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} else if (clGetMemAllocInfoINTEL == nullptr) {
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printf("Couldn't get function pointer for clGetMemAllocInfoINTEL!\n");
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} else {
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cl_int errorCode = CL_SUCCESS;
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size_t gvsize = 0; void* gvptr = nullptr;
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errorCode = clGetDeviceGlobalVariablePointerINTEL(
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device(), program(), "uid67f037ed289236e5____ZL2dg", &gvsize, &gvptr);
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printf("clGetDeviceGlobalVariablePointerINTEL with uid67f037ed289236e5____ZL2dg returned %d: %zu %p\n", errorCode, gvsize, gvptr);
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gvsize = 0; gvptr = nullptr;
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errorCode = clGetDeviceGlobalVariablePointerINTEL(
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device(), program(), "_ZL2dg", &gvsize, &gvptr);
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printf("clGetDeviceGlobalVariablePointerINTEL with _ZL2dg returned %d: %zu %p\n", errorCode, gvsize, gvptr);
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cl_unified_shared_memory_type_intel gvtype = 0;
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errorCode = clGetMemAllocInfoINTEL(
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context(), gvptr, CL_MEM_ALLOC_TYPE_INTEL, sizeof(gvtype), &gvtype, nullptr);
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printf("clGetMemAllocInfoINTEL returned %d: %04X\n", errorCode, gvtype);
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}
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printf("Done.\n");
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return 0;
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}

‎samples/CMakeLists.txt‎

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add_subdirectory( 10_queueexperiments )
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add_subdirectory( 16_floatatomics )
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add_subdirectory( 99_globalvar )
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set(BUILD_EXTENSION_SAMPLES TRUE)
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if(NOT TARGET OpenCLExt)
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message(STATUS "Skipping Extension Samples - OpenCL Extension Loader is not found.")

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