Added ROCmPackage (build system) documentation (#20743)

lib/spack/docs/build_systems.rst

@@ -60,6 +60,7 @@ on these ideas for each distinct build system that Spack supports:
    build_systems/bundlepackage
    build_systems/cudapackage
    build_systems/intelpackage
+   build_systems/rocmpackage
    build_systems/custompackage
 
 For reference, the :py:mod:`Build System API docs <spack.build_systems>`

lib/spack/docs/build_systems/rocmpackage.rst

@@ -0,0 +1,122 @@
+.. Copyright 2013-2021 Lawrence Livermore National Security, LLC and other
+   Spack Project Developers. See the top-level COPYRIGHT file for details.
+
+   SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+.. _rocmpackage:
+
+-----------
+ROCmPackage
+-----------
+
+The ``ROCmPackage`` is not a build system but a helper package. Like ``CudaPackage``,
+it provides standard variants, dependencies, and conflicts to facilitate building
+packages using GPUs though for AMD in this case.
+
+You can find the source for this package (and suggestions for setting up your
+``compilers.yaml`` and ``packages.yaml`` files) at
+`<https://github.com/spack/spack/blob/develop/lib/spack/spack/build_systems/rocm.py>`__.
+
+^^^^^^^^
+Variants
+^^^^^^^^
+
+This package provides the following variants:
+
+* **rocm**
+
+  This variant is used to enable/disable building with ``rocm``.  
+  The default is disabled (or ``False``).
+
+* **amdgpu_target**
+
+  This variant supports the optional specification of the AMD GPU architecture.
+  Valid values are the names of the GPUs (e.g., ``gfx701``), which are maintained
+  in the ``amdgpu_targets`` property.
+
+^^^^^^^^^^^^
+Dependencies
+^^^^^^^^^^^^
+
+This package defines basic ``rocm`` dependencies, including ``llvm`` and ``hip``.
+
+^^^^^^^^^
+Conflicts
+^^^^^^^^^
+
+Conflicts are used to prevent builds with known bugs or issues. This package
+already requires that the ``amdgpu_target`` always be specified for ``rocm``
+builds. It also defines a conflict that prevents builds with an ``amdgpu_target``
+when ``rocm`` is disabled.
+
+Refer to `Conflicts <https://spack.readthedocs.io/en/latest/packaging_guide.html?highlight=conflicts#conflicts>`__
+for more information on package conflicts.
+
+^^^^^^^
+Methods
+^^^^^^^
+
+This package provides one custom helper method, which is used to build
+standard AMD hip compiler flags.
+
+**hip_flags**
+
+    This built-in static method returns the appropriately formatted
+    ``--amdgpu-target`` build option for ``hipcc``.
+
+    This method must be explicitly called when you are creating the
+    arguments for your build in order to use the values.
+
+^^^^^
+Usage
+^^^^^
+
+This helper package can be added to your package by adding it as a base
+class of your package.  For example, you can add it to your
+:ref:`CMakePackage <cmakepackage>`-based package as follows:
+
+.. code-block:: python
+   :emphasize-lines: 1,3-7,14-25
+
+    class MyRocmPackage(CMakePackage, ROCmPackage):
+        ...
+        # Ensure +rocm and amdgpu_targets are passed to dependencies
+        depends_on('mydeppackage', when='+rocm')
+        for val in ROCmPackage.amdgpu_targets:
+            depends_on('mydeppackage amdgpu_target={0}'.format(val),
+                       when='amdgpu_target={0}'.format(val))
+        ...
+
+        def cmake_args(self):
+            spec = self.spec
+            args = []
+            ...
+            if '+rocm' in spec:
+                # Set up the hip macros needed by the build
+                args.extend([
+                    '-DENABLE_HIP=ON',
+                    '-DHIP_ROOT_DIR={0}'.format(spec['hip'].prefix])
+                rocm_archs = spec.variants['amdgpu_target'].value
+                if 'none' not in rocm_archs:
+                    args.append('-DHIP_HIPCC_FLAGS=--amdgpu-target={0}'
+                                .format(",".join(rocm_archs)))
+            else:
+                # Ensure build with hip is disabled
+                args.append('-DENABLE_HIP=OFF')
+            ...
+            return args
+        ...
+
+assuming only on the ``ENABLE_HIP``, ``HIP_ROOT_DIR``, and ``HIP_HIPCC_FLAGS``
+macros are required to be set and the only dependency needing rocm options
+is ``mydeppackage``. You will need to customize the flags as needed for your
+build.
+
+This example also illustrates how to check for the ``rocm`` variant using
+``self.spec`` and how to retrieve the ``amdgpu_target`` variant's value
+using ``self.spec.variants['amdgpu_target'].value``.
+
+All five packages using ``ROCmPackage`` as of January 2021 also use the
+:ref:`CudaPackage <cudapackage>`. So it is worth looking at those packages
+to get ideas for creating a package that can support both ``cuda`` and
+``rocm``.

lib/spack/docs/packaging_guide.rst

@@ -2744,12 +2744,14 @@ The classes that are currently provided by Spack are:
     |                               | built using CMake                |
     +-------------------------------+----------------------------------+
     | :py:class:`.CudaPackage`      | A helper class for packages that |
-    |                               | use CUDA. It is intended to be   |
-    |                               | used in combination with others  |
+    |                               | use CUDA                         |
     +-------------------------------+----------------------------------+
     | :py:class:`.QMakePackage`     | Specialized class for packages   |
     |                               | build using QMake                |
     +-------------------------------+----------------------------------+
+    | :py:class:`.ROCmPackage`      | A helper class for packages that |
+    |                               | use ROCm                         |
+    +-------------------------------+----------------------------------+
     | :py:class:`.SConsPackage`     | Specialized class for packages   |
     |                               | built using SCons                |
     +-------------------------------+----------------------------------+