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DirectXShaderCompiler on Linux & macOS

Introduction

DirectXShaderCompiler (DXC) is based on LLVM/Clang, which is originally cross-platform. However, to support HLSL, certain Windows specific techniques (like COM, SAL, etc.) are introduced to solve technical issues on the Windows platform, which also makes DXC not compilable/runnable on non-Windows platforms.

Upon several requests from the community, we have started the effort to enable compilation and running of DXC on non-Windows platforms (Linux and macOS).

Current Status

Up and Running

We have currently reached the point where we can successfully build and run DXC on Linux and macOS. Code generation works for both DXIL and SPIR-V, and we are also able to run the whole SPIR-V and a large portion of DXIL CodeGen test suite on these platforms.

Note: This work is currently in experimental phase. How we implement certain things for Unix platforms may change without considering backward portability.

Known Limitations

The following targets are currently disabled for non-Windows platforms and this is an area where further contributions can be made:

  • d3dcomp
  • dxa
  • dxopt
  • dxl
  • dxr
  • dxv
  • dxlib-sample

Moreover, since the HLSL CodeGen tests were originally written with Windows in mind, they require the Windows-specific TAEF Framework to run. Besides, some tests also require DirectX to execute. Therefore we are not able to compile/run all these tests on non-Windows platforms. Note that it is only the testing infrastructure that has this limitation, and DXIL CodeGen works as expected by running the DXC executable.

Known Issues

  • Running the SPIR-V CodeGen tests results in opening a large number of file descriptors, and if the OS limitation on the number of FDs allowed to be opened by a process is low, it will cause test failures. We have not seen this as an issue on Windows and Linux. On macOS we currently increase the allowed limit to get around the problem for the time being.
  • The version number of the shared library is currently stuck at 3.7. We need to fix this once a certain versioning scheme is in place.

Building and Using

Build Requirements

Please make sure you have the following resources before building:

  • Git
  • Python. Version 3.x is required.
  • Ninja (Optional CMake generator)
  • Either of gcc/g++ or clang/clang++ compilers. Minimum supported version:
    • GCC version 5.5 or higher.
    • Clang version 3.8 or higher.

Building DXC

You can follow these steps to build DXC on Linux/macOS:

cd <dxc-build-dir>
cmake <dxc-src-dir> -GNinja -DCMAKE_BUILD_TYPE=Release $(cat <dxc-src-dir>/utils/cmake-predefined-config-params)
ninja

Note that cmake-predefined-config-params file contains several cmake configurations that are needed for successful compilation. You can further customize your build by adding configurations at the end of the cmake command above.

For instance, you can use

-DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++

or

-DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++

to choose your desired C/C++ compiler.

You should now have the dxc executable located at <dxc-build-dir>/bin/dxc. And you should be able to successfully run commands as you would on Windows, e.g:

./bin/dxc -help
./bin/dxc -T <target> -E <entry-point-name> <input-hlsl-file>

Note that you cannot use slashes (/) for specifying command line options as you would on Windows. You should use dashes as per usual Unix style.

Building and Running Tests

The tests are run using the GoogleTest framework.

You can follow these steps to build and run the tests:

cd <dxc-build-dir>
# Use SPIRV_BUILD_TESTS flag to enable building these tests.
cmake <dxc-src-dir> \
  $(cat <dxc-src-dir>/utils/cmake-predefined-config-params) \
  -DCMAKE_BUILD_TYPE=Release -DSPIRV_BUILD_TESTS=ON \
  -GNinja
# Build all targets. Includes 'dxc' and tests.
ninja
# Run all tests
ctest

As described in the Known Issues section above, you currently need to increase the maximum per-process open files on macOS using ulimit -Sn 1024 before running the tests on that platform.

TODO: Add more information about Linux implementation details.