Clone this repo:
  1. 7c95a0d Update LLVM (#733) by alan-baker · 6 weeks ago main
  2. af397a5 Update LLVM and remove 3d image write workaround (#726) by Kévin Petit · 7 weeks ago
  3. aab5bb8 Add options for fp16 and fp64 and disable unsupported CL3 features (#722) by Kévin Petit · 7 weeks ago
  4. 589d72e Add support for cl_arm_non_uniform_work_group_size (#720) by Marco Antognini · 8 weeks ago
  5. 7e33840 Fix compilation for 32-bit systems (#717) by Marco Antognini · 9 weeks ago


Clspv is a prototype compiler for a subset of OpenCL C to Vulkan compute shaders.

It consists of:

  • A set of LLVM Module passes to transform a dialect of LLVM IR into a SPIR-V module containing Vulkan compute shaders.
  • A command line compiler tool called ‘clspv’ to compile a subset of OpenCL C into a Vulkan compute shader.

Clspv depends on external projects:


Clspv is licensed under the terms of the Apache 2.0 license. The AUTHORS file lists the copyright owners, while individual credit is given in the CONTRIBUTORS file. To contribute, see

Materials in projects Clspv depends on are licensed under their own terms.

Clspv is not an official Google product.


The compiler is an incomplete prototype, with many rough edges.

The input language is a subset of OpenCL C version 1.2. The OpenCL C on Vulkan Specification describes the specific subset, and also the mapping into Vulkan compute shaders.


Compile a set of kernels into a SPIR-V binary module:

clspv -o foo.spv

Emit the binary as a C initializer list, for easy embedding of a shader in in a C or C++ program source:

clspv -mfmt=c -o -

Predefine some preprocessor symbols:

clspv -DWIDTH=32 -DHEIGHT=64 -o foo.spv

Use OpenCL compiler options:

clspv -cl-fast-relaxed-math -cl-single-precision-constant -o foo.spv

Show help:

clspv -help



You will need:

  • CMake
  • Python3
  • A C++ compiler
  • git

Getting sources for dependencies

Clspv depends on the sources for other projects, at specific commits. Run the following command to download those dependencies, and place them in the third_party directory:

python3 utils/


Then, create a build directory:

cd <clspv-dir>
mkdir build
cd build

Then configure and build the code:

cmake <clspv-dir>
cmake --build .

This will build the clspv command line compiler and place it in location bin/clspv under the build directory.

Using Ninja to build, and other build options

We recommend you use the Ninja build tool if it's available. To do so, replace the last two commands with:

cmake -G Ninja <clspv-dir>

Other useful configuration options (the first cmake command):

  • -DCMAKE_BUILD_TYPE=RelWithDebInfo : Build in release mode, with debugging information. Default is a debug build.

See the CMake documentation for more generic options.


To run the test suite from within the build directory:

cmake --build . --target check-spirv

Or if you are using Ninja:

ninja check-spirv

Builtin Library

Clspv includes an LLVM IR library (cmake/clspv--.bc) containing implementations of some OpenCL builtin functions. This file is distributed under the LLVM license (included in LICENSE) as it is generated from the LLVM sub-project libclc. Refer to the source for the relevant copyrights.

Rebuilding the Library

Required Tools

You will need a pre-built version of LLVM for your system, CMake, and (optionally) Ninja.


To rebuild the library run the following commands:

cmake -GNinja -DLIBCLC_TARGETS_TO_BUILD=“clspv--” -DLLVM_CONFIG= ninja

Copy the resulting clspv--.bc into the cmake/ directory and rebuild clspv.