[SYCL] Add the ability to install the OpenCL ICD loader with LLVM

In certain cases one will want to install the same OpenCL ICD library
along with LLVM that the code was built against. The new option,
OpenCL_INSTALL_KHRONOS_ICD_LOADER can be used to set this up.

- Add the (conditional) installation of the OpenCL ICD library to the
deploy-sycl-toolchain target.
- Add a protection for not trying to install the OpenCL ICD library, if
it is not being built. This is meant to avoid running into issues when
the user mis-configures the build.

Author: krasznaa

sycl/CMakeLists.txt

@@ -71,7 +71,7 @@ set(SYCL_INCLUDE_DEPLOY_DIR ${CMAKE_INSTALL_PREFIX}/${SYCL_INCLUDE_DIR})
 # build SYCL runtime.
 # WARNING: use with caution, building SYCL runtime with OpenCL implementation
 # instead of Khronos ICD loader might cause build and/or portability issues.
-option(OpenCL_BUILD_WITH_SYSTEM_SDK OFF)
+option(OpenCL_BUILD_WITH_SYSTEM_SDK "Build SYCL with OpenCL coming from the build system" OFF)
 
 if( (OpenCL_INCLUDE_DIR AND OpenCL_LIBRARY) OR OpenCL_BUILD_WITH_SYSTEM_SDK)
   find_package(OpenCL)
@@ -80,7 +80,7 @@ endif()
 include(ExternalProject)
 
 if( NOT OpenCL_INCLUDE_DIRS )
-  message("OpenCL_INCLUDE_DIRS is missing. Will try to download OpenCL headers from github.com")
+  message(STATUS "OpenCL_INCLUDE_DIRS is missing. Will try to download OpenCL headers from github.com")
   set(OpenCL_INCLUDE_DIRS "${CMAKE_CURRENT_BINARY_DIR}/OpenCL/inc")
   ExternalProject_Add(ocl-headers
     GIT_REPOSITORY    https://github.com/KhronosGroup/OpenCL-Headers.git
@@ -102,7 +102,7 @@ else()
 endif()
 
 if( NOT OpenCL_LIBRARIES )
-  message("OpenCL_LIBRARIES is missing. Will try to download OpenCL ICD Loader from github.com")
+  message(STATUS "OpenCL_LIBRARIES is missing. Will try to download OpenCL ICD Loader from github.com")
   if(MSVC)
     set(OpenCL_LIBRARIES
         "${LLVM_LIBRARY_OUTPUT_INTDIR}/${CMAKE_STATIC_LIBRARY_PREFIX}OpenCL${CMAKE_STATIC_LIBRARY_SUFFIX}")
@@ -123,16 +123,31 @@ if( NOT OpenCL_LIBRARIES )
     GIT_TAG           origin/master
     SOURCE_DIR        "${CMAKE_CURRENT_BINARY_DIR}/OpenCL/icd"
     BINARY_DIR        "${CMAKE_CURRENT_BINARY_DIR}/icd_build"
+    INSTALL_DIR       "${CMAKE_CURRENT_BINARY_DIR}/icd_install"
     CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
                -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
                -DOPENCL_ICD_LOADER_HEADERS_DIR=${OpenCL_INCLUDE_DIRS}
-               -DCMAKE_INSTALL_PREFIX=${LLVM_BINARY_DIR}
+               -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
                -DCMAKE_INSTALL_LIBDIR:PATH=lib${LLVM_LIBDIR_SUFFIX}
                ${AUX_CMAKE_FLAGS}
     STEP_TARGETS      configure,build,install
     DEPENDS           ocl-headers
     BUILD_BYPRODUCTS ${OpenCL_LIBRARIES}
   )
+  ExternalProject_Add_Step(ocl-icd llvminstall
+    COMMAND ${CMAKE_COMMAND} -E copy_directory <INSTALL_DIR>/ ${LLVM_BINARY_DIR}
+    COMMENT "Installing ocl-icd into the LLVM binary directory"
+    DEPENDEES install
+  )
+  # Optionally install the ICD library along with LLVM.
+  option(OpenCL_INSTALL_KHRONOS_ICD_LOADER
+    "Install the Khronos ICD Loader built as part of LLVM" OFF)
+  if (OpenCL_INSTALL_KHRONOS_ICD_LOADER)
+    install(DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/icd_install/"
+      DESTINATION "."
+      COMPONENT opencl-icd
+    )
+  endif()
 else()
   file(GLOB ICD_LOADER_SRC "${OpenCL_LIBRARIES}*")
   file(COPY ${ICD_LOADER_SRC} DESTINATION ${LLVM_LIBRARY_OUTPUT_INTDIR})
@@ -291,6 +306,9 @@ set( SYCL_TOOLCHAIN_DEPLOY_COMPONENTS
      pi_opencl
      libsycldevice
 )
+if(OpenCL_INSTALL_KHRONOS_ICD_LOADER AND TARGET ocl-icd)
+  list(APPEND SYCL_TOOLCHAIN_DEPLOY_COMPONENTS opencl-icd)
+endif()
 
 if(SYCL_BUILD_PI_CUDA)
   # Ensure that libclc is enabled.