Building Slang From Source

Making it easier to work with shaders

Building Slang From Source

TLDR

cmake --workflow --preset release to configure, build, and package a release version of Slang.

Prerequisites:

Please install:

  • CMake (3.25 preferred, but 3.22 works[^1])
  • A C++ compiler with support for C++17. GCC, Clang and MSVC are supported
  • A CMake compatible backend, for example Visual Studio or Ninja
  • Python3 (a dependency for building spirv-tools)

Optional dependencies for tests include

  • CUDA
  • OptiX
  • NVAPI
  • Aftermath
  • X11

Other dependencies are sourced from submodules in the ./external directory.

Get the Source Code

Clone this repository. Make sure to fetch the submodules also.

git clone https://github.com/shader-slang/slang --recursive

Configure and build

This section assumes cmake 3.25 or greater, if you’re on a lower version please see building with an older cmake

For a Ninja based build system (all platforms) run:

cmake --preset default
cmake --build --preset releaseWithDebugInfo # or --preset debug, or --preset release

For Visual Studio run:

cmake --preset vs2022 # or 'vs2019' or `vs2022-dev`
start devenv ./build/slang.sln # to optionally open the project in Visual Studio
cmake --build --preset releaseWithDebugInfo # to build from the CLI, could also use --preset release or --preset debug

There also exists a vs2022-dev preset which turns on features to aid debugging.

WebAssembly build

In order to build WebAssembly build of Slang, Slang needs to be compiled with Emscripten SDK. You can find more information about Emscripten.

You need to clone the EMSDK repo. And you need to install and activate the latest.

git clone https://github.com/emscripten-core/emsdk.git
cd emsdk

For non-Windows platforms

./emsdk install latest
./emsdk activate latest

For Windows

emsdk.bat install latest
emsdk.bat activate latest

After EMSDK is activated, Slang needs to be built in a cross compiling setup:

  • build the generators target for the build platform
  • configure the build with emcmake for the host platform
  • build for the host platform.

Note: For more details on cross compiling please refer to the cross-compiling section.

# Build generators.
cmake --workflow --preset generators --fresh
mkdir generators
cmake --install build --prefix generators --component generators

# Configure the build with emcmake.
# emcmake is available only when emsdk_env setup the environment correctly.
pushd ../emsdk
source ./emsdk_env # For Windows, emsdk_env.bat
popd
emcmake cmake -DSLANG_GENERATORS_PATH=generators/bin --preset emscripten -G "Ninja"

# Build slang-wasm.js and slang-wasm.wasm in build.em/Release/bin
cmake --build --preset emscripten --target slang-wasm

Note: If the last build step fails, try running the command that emcmake outputs, directly.

Testing

build/Debug/bin/slang-test

See the documentation on testing for more information.

More niche topics

CMake options

Option Default Description
SLANG_VERSION Latest v* tag The project version, detected using git if available
SLANG_EMBED_CORE_MODULE TRUE Build slang with an embedded version of the core module
SLANG_EMBED_CORE_MODULE_SOURCE TRUE Embed the core module source in the binary
SLANG_ENABLE_ASAN FALSE Enable ASAN (address sanitizer)
SLANG_ENABLE_FULL_IR_VALIDATION FALSE Enable full IR validation (SLOW!)
SLANG_ENABLE_IR_BREAK_ALLOC FALSE Enable IR BreakAlloc functionality for debugging.
SLANG_ENABLE_GFX TRUE Enable gfx targets
SLANG_ENABLE_SLANGD TRUE Enable language server target
SLANG_ENABLE_SLANGC TRUE Enable standalone compiler target
SLANG_ENABLE_SLANGRT TRUE Enable runtime target
SLANG_ENABLE_SLANG_GLSLANG TRUE Enable glslang dependency and slang-glslang wrapper target
SLANG_ENABLE_TESTS TRUE Enable test targets, requires SLANG_ENABLE_GFX, SLANG_ENABLE_SLANGD and SLANG_ENABLE_SLANGRT
SLANG_ENABLE_EXAMPLES TRUE Enable example targets, requires SLANG_ENABLE_GFX
SLANG_LIB_TYPE SHARED How to build the slang library
SLANG_SLANG_LLVM_FLAVOR FETCH_BINARY_IF_POSSIBLE How to set up llvm support
SLANG_SLANG_LLVM_BINARY_URL System dependent URL specifying the location of the slang-llvm prebuilt library
SLANG_GENERATORS_PATH `` Path to an installed all-generators target for cross compilation

The following options relate to optional dependencies for additional backends and running additional tests. Left unchanged they are auto detected, however they can be set to OFF to prevent their usage, or set to ON to make it an error if they can’t be found.

Option CMake hints Notes
SLANG_ENABLE_CUDA CUDAToolkit_ROOT CUDA_PATH Enable running tests with the CUDA backend, doesn’t affect the targets Slang itself supports
SLANG_ENABLE_OPTIX Optix_ROOT_DIR Requires CUDA
SLANG_ENABLE_NVAPI NVAPI_ROOT_DIR Only available for builds targeting Windows
SLANG_ENABLE_AFTERMATH Aftermath_ROOT_DIR Enable Aftermath in GFX, and add aftermath crash example to project
SLANG_ENABLE_XLIB    

Advanced options

Option Default Description
SLANG_ENABLE_DX_ON_VK FALSE Enable running the DX11 and DX12 tests on non-warning Windows platforms via vkd3d-proton, requires system-provided d3d headers
SLANG_ENABLE_SLANG_RHI TRUE Enable building and using slang-rhi for tests
SLANG_USE_SYSTEM_MINIZ FALSE Build using system Miniz library instead of the bundled version in ./external
SLANG_USE_SYSTEM_LZ4 FALSE Build using system LZ4 library instead of the bundled version in ./external
SLANG_USE_SYSTEM_VULKAN_HEADERS FALSE Build using system Vulkan headers instead of the bundled version in ./external
SLANG_USE_SYSTEM_SPIRV_HEADERS FALSE Build using system SPIR-V headers instead of the bundled version in ./external
SLANG_USE_SYSTEM_UNORDERED_DENSE FALSE Build using system unordered dense instead of the bundled version in ./external
SLANG_SPIRV_HEADERS_INCLUDE_DIR `` Use this specific path to SPIR-V headers instead of the bundled version in ./external

LLVM Support

There are several options for getting llvm-support:

  • Use a prebuilt binary slang-llvm library: -DSLANG_SLANG_LLVM_FLAVOR=FETCH_BINARY or -DSLANG_SLANG_LLVM_FLAVOR=FETCH_BINARY_IF_POSSIBLE (this is the default)
    • You can set SLANG_SLANG_LLVM_BINARY_URL to point to a local libslang-llvm.so/slang-llvm.dll or set it to a URL of an zip/archive containing such a file
    • If this isn’t set then the build system tries to download it from the release on github matching the current tag. If such a tag doesn’t exist or doesn’t have the correct os*arch combination then the latest release will be tried.
    • If SLANG_SLANG_LLVM_BINARY_URL is FETCH_BINARY_IF_POSSIBLE then in the case that a prebuilt binary can’t be found then the build will proceed as though DISABLE was chosen
  • Use a system supplied LLVM: -DSLANG_SLANG_LLVM_FLAVOR=USE_SYSTEM_LLVM, you must have llvm-13.0 and a matching libclang installed. It’s important that either:
    • You don’t end up linking to a dynamic libllvm.so, this will almost certainly cause multiple versions of LLVM to be loaded at runtime, leading to errors like opt: CommandLine Error: Option 'asm-macro-max-nesting-depth' registered more than once!. Avoid this by compiling LLVM without the dynamic library.
    • Anything else which may be linked in (for example Mesa, also dynamically loads the same llvm object)
  • Do not enable LLVM support: -DSLANG_SLANG_LLVM_FLAVOR=DISABLE

To build only a standalone slang-llvm, you can run:

cmake --workflow --preset slang-llvm

This will generate build/dist-release/slang-slang-llvm.zip containing the library. This, of course, uses the system LLVM to build slang-llvm, otherwise it would just be a convoluted way to download a prebuilt binary.

Cross compiling

Slang generates some code at build time, using generators build from this codebase. Due to this, for cross compilation one must already have built these generators for the build platform. Build them with the generators preset, and pass the install path to the cross building CMake invocation using SLANG_GENERATORS_PATH

Non-Windows platforms:

# build the generators
cmake --workflow --preset generators --fresh
mkdir build-platform-generators
cmake --install build --config Release --prefix build-platform-generators --component generators
# reconfigure, pointing to these generators
# Here is also where you should set up any cross compiling environment
cmake \
  --preset default \
  --fresh \
  -DSLANG_GENERATORS_PATH=build-platform-generators/bin \
  -Dwhatever-other-necessary-options-for-your-cross-build \
  # for example \
  -DCMAKE_C_COMPILER=my-arch-gcc \
  -DCMAKE_CXX_COMPILER=my-arch-g++
# perform the final build
cmake --workflow --preset release

Windows

# build the generators
cmake --workflow --preset generators --fresh
mkdir build-platform-generators
cmake --install build --config Release --prefix build-platform-generators --component generators
# reconfigure, pointing to these generators
# Here is also where you should set up any cross compiling environment
# For example
./vcvarsamd64_arm64.bat
cmake \
  --preset default \
  --fresh \
  -DSLANG_GENERATORS_PATH=build-platform-generators/bin \
  -Dwhatever-other-necessary-options-for-your-cross-build
# perform the final build
cmake --workflow --preset release

Example cross compiling with MSVC to windows-aarch64

One option is to build using the ninja generator, which requires providing the native and cross environments via vcvarsall.bat

vcvarsall.bat
cmake --workflow --preset generators --fresh
mkdir generators
cmake --install build --prefix generators --component generators
vsvarsall.bat x64_arm64
cmake --preset default --fresh -DSLANG_GENERATORS_PATH=generators/bin
cmake --workflow --preset release

Another option is to build using the Visual Studio generator which can find this automatically

cmake --preset vs2022 # or --preset vs2019
cmake --build --preset generators # to build from the CLI
cmake --install build --prefix generators --component generators
rm -rf build # The Visual Studio generator will complain if this is left over from a previous build
cmake --preset vs2022 --fresh -A arm64 -DSLANG_GENERATORS_PATH=generators/bin
cmake --build --preset release

Building with an older CMake

Because older CMake versions don’t support all the features we want to use in CMakePresets, you’ll have to do without the presets. Something like the following

cmake -B build -G Ninja
cmake --build build -j

Notes

[^1] below 3.25, CMake lacks the ability to mark directories as being system directories (https://cmake.org/cmake/help/latest/prop_tgt/SYSTEM.html#prop_tgt:SYSTEM), this leads to an inability to suppress warnings originating in the dependencies in ./external, so be prepared for some additional warnings.