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Diffstat (limited to 'libc/docs/gpu/using.rst')
| -rw-r--r-- | libc/docs/gpu/using.rst | 33 |
1 files changed, 17 insertions, 16 deletions
diff --git a/libc/docs/gpu/using.rst b/libc/docs/gpu/using.rst index 71f5e7b..79b9116 100644 --- a/libc/docs/gpu/using.rst +++ b/libc/docs/gpu/using.rst @@ -14,25 +14,25 @@ Building the GPU library LLVM's libc GPU support *must* be built with an up-to-date ``clang`` compiler due to heavy reliance on ``clang``'s GPU support. This can be done automatically -using the ``LLVM_ENABLE_RUNTIMES=libc`` option. To enable libc for the GPU, -enable the ``LIBC_GPU_BUILD`` option. By default, ``libcgpu.a`` will be built -using every supported GPU architecture. To restrict the number of architectures -build, either set ``LIBC_GPU_ARCHITECTURES`` to the list of desired -architectures manually or use ``native`` to detect the GPUs on your system. A -typical ``cmake`` configuration will look like this: +using the LLVM runtimes support. The GPU build is done using cross-compilation +to the GPU architecture. This project currently supports AMD and NVIDIA GPUs +which can be targeted using the appropriate target name. The following +invocation will enable a cross-compiling build for the GPU architecture and +enable the ``libc`` project only for them. .. code-block:: sh $> cd llvm-project # The llvm-project checkout $> mkdir build $> cd build - $> cmake ../llvm -G Ninja \ - -DLLVM_ENABLE_PROJECTS="clang;lld;compiler-rt" \ - -DLLVM_ENABLE_RUNTIMES="libc;openmp" \ + $> cmake ../llvm -G Ninja \ + -DLLVM_ENABLE_PROJECTS="clang;lld;compiler-rt" \ + -DLLVM_ENABLE_RUNTIMES="openmp" \ -DCMAKE_BUILD_TYPE=<Debug|Release> \ # Select build type - -DLIBC_GPU_BUILD=ON \ # Build in GPU mode - -DLIBC_GPU_ARCHITECTURES=all \ # Build all supported architectures - -DCMAKE_INSTALL_PREFIX=<PATH> \ # Where 'libcgpu.a' will live + -DCMAKE_INSTALL_PREFIX=<PATH> \ # Where 'libcgpu.a' will live + -DRUNTIMES_nvptx64-nvidia-cuda_LLVM_ENABLE_RUNTIMES=libc \ + -DRUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES=libc \ + -DLLVM_RUNTIME_TARGETS=default;amdgcn-amd-amdhsa;nvptx64-nvidia-cuda $> ninja install Since we want to include ``clang``, ``lld`` and ``compiler-rt`` in our @@ -40,13 +40,14 @@ toolchain, we list them in ``LLVM_ENABLE_PROJECTS``. To ensure ``libc`` is built using a compatible compiler and to support ``openmp`` offloading, we list them in ``LLVM_ENABLE_RUNTIMES`` to build them after the enabled projects using the newly built compiler. ``CMAKE_INSTALL_PREFIX`` specifies the installation -directory in which to install the ``libcgpu.a`` library and headers along with -LLVM. The generated headers will be placed in ``include/gpu-none-llvm``. +directory in which to install the ``libcgpu-nvptx.a`` and ``libcgpu-amdgpu.a`` +libraries and headers along with LLVM. The generated headers will be placed in +``include/<gpu-triple>``. Usage ===== -Once the ``libcgpu.a`` static archive has been built it can be linked directly +Once the static archive has been built it can be linked directly with offloading applications as a standard library. This process is described in the `clang documentation <https://clang.llvm.org/docs/OffloadingDesign.html>`_. This linking mode is used by the OpenMP toolchain, but is currently opt-in for @@ -68,7 +69,7 @@ supported target device. The supported architectures can be seen using LLVM's OFFLOADING IMAGE [0]: kind llvm ir - arch gfx90a + arch generic triple amdgcn-amd-amdhsa producer none |