OpenCL

The OpenCL support for the nu+ architecture is made through pocl.

How to install vanilla pocl

1. Download following the link.
2. In order to build pocl, you need the following support libraries and tools:
   • Latest released version of LLVM & Clang
   • GNU make
   • libtool dlopen wrapper files (e.g. libltdl3-dev in Debian)
   • pthread (should be installed by default)
   • hwloc v1.0 or newer (e.g. libhwloc-dev)
   • pkg-config
   • cmake
   • libclang-3.8-dev if you are using Ubuntu 16.04 LTS

   On Ubuntu 16.04 LTS you can run the following code on a terminal

   sudo apt-get install llvm & clang & libltdl3-dev & libhwloc-dev & libhwloc-dev & libclang-3.8-dev & make & cmake

3. Build and install

   cd <directory-with-pocl-sources>
   mkdir build
   cd build
   cmake [-D<option>=<value> ...] ..
   make && make install

Using pocl

To compile with pocl you have to execute:

gcc example1.c -o example `pkg-config --libs --cflags pocl`

See [1] and [2] for further informations.

Modify pocl

Adding a new device class in pocl

• Create a directory for the new device class in "lib/CL/devices". In this case the "nuplus" folder is created.
• Create at least the files newdevice.c and newdevice.h. In this case "nuplus.c" and "nuplus.h"
• Create the CMakeList.txt file in the device folder, specifying the files created before and the device name.

   if(MSVC)
   set_source_files_properties( nuplus.h nuplus.c PROPERTIES LANGUAGE CXX )
   endif(MSVC)
   add_library("pocl-devices-nuplus" OBJECT nuplus.h nuplus.c)

• Modify the "lib/CL/devices.c" file including the new header file for the device and adding the init fucntion in the vector pocl_devices_init_ops

  # include "nuplus/nuplus.h"
  
   ...
  
   static init_device_ops pocl_devices_init_ops[] = {
   pocl_pthread_init_device_ops,
   pocl_basic_init_device_ops,
   pocl_nuplus_init_device_ops,
  # if defined(TCE_AVAILABLE)
   pocl_ttasim_init_device_ops,
  # endif
  # if defined(BUILD_HSA)
   pocl_hsa_init_device_ops,
  # endif
   };
  
   ...

• Modify the "lib/CL/devices/CMakeLists.txt" adding the new device subdirectory name.

   ...
  
   add_subdirectory("nuplus")
  
   ...

• Modify the "CMakeLists.txt" in the pocl root directory adding the new device name to the "OCL_DRIVERS".

   ...
  
   set(OCL_DRIVERS "basic pthreads nuplus")
  
   ...

Build pocl with a custom LLVM

Prerequisites

Be sure that the LLVM compiler is built with all the targets and the default target is set as the host. For the nu+ toolchain the CMakeLists.txt in the LLVM root folder must be modified as reported below:

1. Delete the code

   set(LLVM_TARGETS_TO_BUILD "NuPlus"
       CACHE STRING "Semicolon-separated list of targets to build, or \"all\".")

2. modify

   set(LLVM_DEFAULT_TARGET_TRIPLE "nuplus-none-none" CACHE STRING

   in

   set(LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_HOST_TRIPLE}" CACHE STRING