This project implements a virtual OpenCL device simulator, including an OpenCL runtime with ICD support. The goal is to provide a platform for creating tools to aid OpenCL development. In particular, this project currently implements utilities for debugging memory access errors, detecting data-races and barrier divergence, collecting instruction histograms, and for interactive OpenCL kernel debugging. The simulator is built on an interpreter for LLVM IR. This project was originally created by James Price and Simon McIntosh-Smith at the University of Bristol.
Binary releases can be found on the GitHub releases page:
https://github.com/jrprice/Oclgrind/releases
To build this project, you will need LLVM and Clang 11.0 (or newer)
development libraries and headers. If you build LLVM from source, it
is recommended to enable optimizations to significantly improve the
performance of Oclgrind (set CMAKE_BUILD_TYPE to Release or
RelWithDebInfo).
You will need to use a compiler that supports C++14. Python should also be available in order to run the test suite.
The recommended method of building Oclgrind is via CMake.
When configuring the CMake build, you may be prompted to supply a
value for the LLVM_DIR parameter (this shouldn't be necessary if
LLVM is installed in a standard system location). This should be set
to the directory containing your LLVM installation's
LLVMConfig.cmake file (typically either
${LLVM_ROOT}/lib/cmake/llvm or ${LLVM_ROOT}/share/llvm/cmake/).
If Clang is installed separately to LLVM, then you may also be
prompted to supply a path for the CLANG_ROOT parameter, which should
be the root of your Clang installation (containing the bin/, lib/
and include/ directories).
A typical CMake command-line might look like this:
cmake ${OCLGRIND_SOURCE} \
-DCMAKE_BUILD_TYPE=RelWithDebInfo \
-DCMAKE_INSTALL_PREFIX=${INSTALL_ROOT} \
-DLLVM_DIR=${LLVM_ROOT}/lib/cmake/llvm
where ${OCLGRIND_SOURCE} is the path to the root directory
containing the Oclgrind source code, ${LLVM_ROOT} is the path to the
LLVM installation, and ${INSTALL_ROOT} is the desired installation
root directory (this can be omitted if installing to system
directories).
Next, build and install with make:
make
make test
make install
If installing to a non-system location, you should add the bin/
directory to the PATH environment variable in order to make use of
the oclgrind command. If you wish to use Oclgrind via the OpenCL ICD
loader (optional), then you should create an ICD loading point by
copying the oclgrind.icd file from the build directory to
/etc/OpenCL/vendors/.
Building Oclgrind on Windows requires Visual Studio 2017 (or newer).
When configuring the CMake build, you may be prompted to supply a
value for the LLVM_DIR parameter. This should be set to the
directory containing your LLVM installation's LLVMConfig.cmake file
(for example C:\Program Files\LLVM\lib\cmake\llvm). If Clang is
installed separately to LLVM, then you may also be prompted to supply
a path in the CLANG_ROOT parameter, which should be the root of your
Clang installation (containing the bin/, lib/ and include/
directories).
You should add the bin directory of the Oclgrind installation to the
PATH environment variable in order to make use of the oclgrind
command. If you wish to use Oclgrind via the OpenCL ICD loader
(optional), then you should also create an ICD loading point. To do
this, you should add a REG_DWORD value to the Windows Registry under
one or both of the registry keys below, with the name set to the
absolute path of the oclgrind-rt-icd.dll library and the value set
to 0.
Key for 32-bit machines or 64-bit apps on a 64-bit machine:
HKEY_LOCAL_MACHINE\SOFTWARE\Khronos\OpenCL\Vendors
Key for 32-bit apps on a 64-bit machine:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Khronos\OpenCL\Vendors
The recommended method of running an application with Oclgrind is to
use the oclgrind command, for example:
oclgrind ./application
This command will make it such the only OpenCL platform and device
available to your application is Oclgrind. If you need more control
over platform selection then installing an ICD loading point for
Oclgrind will cause it to appear when an application calls
clGetPlatformIDs(), alongside any other OpenCL platforms installed
on your system.
If it encounters any invalid memory accesses, Oclgrind will report the details to stderr, for example:
Invalid write of size 4 at global memory address 0x1000000000040
Kernel: vecadd
Entity: Global(16,0,0) Local(0,0,0) Group(16,0,0)
store i32 %tmp9, i32 addrspace(1)* %tmp15, align 4
At line 4 of input.cl
c[i] = a[i] + b[i]
Since it is interpreting an abstract intermediate representation and bounds-checking each memory access, Oclgrind will run quite slowly (typically a couple of orders of magnitude slower than a regular CPU implementation). Therefore, it is recommended to run your application with a small problem if possible.
To enable an interactive, GDB-style debugging session, supply the -i
flag to the oclgrind command, or export the environment variable
OCLGRIND_INTERACTIVE=1. This will cause Oclgrind to automatically
break at the beginning of each kernel invocation, and upon
encountering an invalid memory access. Type help for details of
available commands.
For more detailed information about using Oclgrind please visit the GitHub Wiki:
https://github.com/jrprice/Oclgrind/wiki/
If you encounter any issues or have any questions, please use the GitHub issues page: