Q: Can OpenMP offloading compile for multiple architectures?
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Since LLVM version 15.0, OpenMP offloading supports offloading to multiple
-architectures at once. This allows for executables to be run on different
-targets, such as offloading to AMD and NVIDIA GPUs simultaneously, as well as
-multiple sub-architectures for the same target. Additionally, static libraries
-will only extract archive members if an architecture is used, allowing users to
+Since LLVM version 15.0, OpenMP offloading supports offloading to multiple
+architectures at once. This allows for executables to be run on different
+targets, such as offloading to AMD and NVIDIA GPUs simultaneously, as well as
+multiple sub-architectures for the same target. Additionally, static libraries
+will only extract archive members if an architecture is used, allowing users to
create generic libraries.
-The architecture can either be specified manually using ``--offload-arch=``. If
-``--offload-arch=`` is present no ``-fopenmp-targets=`` flag is present then the
-targets will be inferred from the architectures. Conversely, if
-``--fopenmp-targets=`` is present with no ``--offload-arch`` then the target
-architecture will be set to a default value, usually the architecture supported
+The architecture can either be specified manually using ``--offload-arch=``. If
+``--offload-arch=`` is present no ``-fopenmp-targets=`` flag is present then the
+targets will be inferred from the architectures. Conversely, if
+``--fopenmp-targets=`` is present with no ``--offload-arch`` then the target
+architecture will be set to a default value, usually the architecture supported
by the system LLVM was built on.
-For example, an executable can be built that runs on AMDGPU and NVIDIA hardware
+For example, an executable can be built that runs on AMDGPU and NVIDIA hardware
given that the necessary build tools are installed for both.
.. code-block:: shell
clang example.c -fopenmp --offload-arch=gfx90a --offload-arch=sm_80
-If just given the architectures we should be able to infer the triples,
+If just given the architectures we should be able to infer the triples,
otherwise we can specify them manually.
.. code-block:: shell
-Xopenmp-target=amdgcn-amd-amdhsa --offload-arch=gfx90a \
-Xopenmp-target=nvptx64-nvidia-cuda --offload-arch=sm_80
-When linking against a static library that contains device code for multiple
+When linking against a static library that contains device code for multiple
architectures, only the images used by the executable will be extracted.
.. code-block:: shell
llvm-ar rcs libexample.a example.o
clang app.c -fopenmp --offload-arch=gfx90a -o app
-The supported device images can be viewed using the ``--offloading`` option with
+The supported device images can be viewed using the ``--offloading`` option with
``llvm-objdump``.
.. code-block:: shell
arch sm_80
triple nvptx64-nvidia-cuda
producer openmp
+
+Q: Can I link OpenMP offloading with CUDA or HIP?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+OpenMP offloading files can currently be experimentally linked with CUDA and HIP
+files. This will allow OpenMP to call a CUDA device function or vice-versa.
+However, the global state will be distinct between the two images at runtime.
+This means any global variables will potentially have different values when
+queried from OpenMP or CUDA.
+
+Linking CUDA and HIP currently requires enabling a different compilation mode
+for CUDA / HIP with ``--offload-new-driver`` and to link using
+``--offload-link``. Additionally, ``-fgpu-rdc`` must be used to create a
+linkable device image.
+
+.. code-block:: shell
+
+ clang++ openmp.cpp -fopenmp --offload-arch=sm_80 -c
+ clang++ cuda.cu --offload-new-driver --offload-arch=sm_80 -fgpu-rdc -c
+ clang++ openmp.o cuda.o --offload-link -o app