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Code Object Manager (Comgr)

The Comgr library provides APIs for compiling and inspecting AMDGPU code objects. The API is documented in the header file.

Building the Code Object Manager

Comgr depends on LLVM and AMDDeviceLibs. One way to make these visible to the Comgr build process is by setting the CMAKE_PREFIX_PATH to include either the build directory or install prefix of each of these components, separated by a semicolon. Both should be built using either sources with the same ROCm release tag, or from the amd-staging branch. LLVM should be built with at least LLVM_ENABLE_PROJECTS='llvm;clang;lld' and LLVM_TARGETS_TO_BUILD='AMDGPU;X86'.

An example bash session to build Comgr on Linux using GNUMakefiles is:

$ LLVM_PROJECT=~/llvm-project
$ DEVICE_LIBS=~/llvm-project/amd/device-libs
$ COMGR=~/llvm-project/amd/comgr
$ mkdir -p "$LLVM_PROJECT/build"
$ cd "$LLVM_PROJECT/build"
$ cmake \
    -DCMAKE_BUILD_TYPE=Release \
    -DLLVM_ENABLE_PROJECTS="llvm;clang;lld" \
    -DLLVM_TARGETS_TO_BUILD="AMDGPU;X86" \
    ../llvm
$ make
$ mkdir -p "$DEVICE_LIBS/build"
$ cd "$DEVICE_LIBS/build"
$ cmake \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_PREFIX_PATH="$LLVM_PROJECT/build" \
    ..
$ make
$ mkdir -p "$COMGR/build"
$ cd "$COMGR/build"
$ cmake \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_PREFIX_PATH="$LLVM_PROJECT/build;$DEVICE_LIBS/build" \
    ..
$ make
$ make test

The equivalent on Windows in cmd.exe using Visual Studio project files is:

> set LLVM_PROJECT="%HOMEPATH%\llvm-project"
> set DEVICE_LIBS="%HOMEPATH%\llvm-project\amd\device-libs"
> set COMGR="%HOMEPATH%\llvm-project\amd\comgr"
> mkdir "%LLVM_PROJECT%\build"
> cd "%LLVM_PROJECT%\build"
> cmake ^
    -DLLVM_ENABLE_PROJECTS="llvm;clang;lld" ^
    -DLLVM_TARGETS_TO_BUILD="AMDGPU;X86" ^
    ..\llvm
> msbuild /p:Configuration=Release ALL_BUILD.vcxproj
> mkdir "%DEVICE_LIBS%\build"
> cd "%DEVICE_LIBS%\build"
> cmake ^
    -DCMAKE_PREFIX_PATH="%LLVM_PROJECT%\build" ^
    ..
> msbuild /p:Configuration=Release ALL_BUILD.vcxproj
> mkdir "%COMGR%\build"
> cd "%COMGR%\build"
> cmake ^
    -DCMAKE_PREFIX_PATH="%LLVM_PROJECT%\build;%DEVICE_LIBS%\build" ^
    ..
> msbuild /p:Configuration=Release ALL_BUILD.vcxproj
> msbuild /p:Configuration=Release RUN_TESTS.vcxproj

Optionally, AddressSanitizer may be enabled during development via -DADDRESS_SANITIZER=On during the Comgr cmake step.

Depending on the Code Object Manager

Comgr exports a CMake package named amd_comgr for both the build and install trees. This package defines a library target named amd_comgr. To depend on this in your CMake project, use find_package:

find_package(amd_comgr REQUIRED CONFIG)
...
target_link_libraries(your_target amd_comgr)

If Comgr is not installed to a standard CMake search directory, the path to the build or install tree can be supplied to CMake via CMAKE_PREFIX_PATH:

cmake -DCMAKE_PREFIX_PATH=path/to/comgr/build/or/install

Environment Variables

Comgr lazily evaluates certain environment variables when their value is first required. If the value is used, it is read once at the time it is needed, and then cached. The exact behavior when changing these values during the execution of a process after Comgr APIs have been invoked is undefined.

Comgr supports some environment variables to locate parts of the ROCm stack. These include:

  • ROCM_PATH: If this is set it is used as an absolute path to the root of the ROCm installation, which is used when determining the default values for HIP_PATH and LLVM_PATH (see below). If this is not set and if a ROCM package is provided during the build, ROCM path is set to it. Otherwise Comgr tries to construct the ROCM path from the path where amd_comgr library is located.
  • HIP_PATH: If this is set it is used as an absolute path to the root of the HIP installation. If this is not set, it has a default value of "${ROCM_PATH}/hip".
  • LLVM_PATH: If this is set it is used as an absolute path to the root of the LLVM installation, which is currently used for HIP compilation to locate certain runtime headers. If this is not set, it has a default value of "${ROCM_PATH}/llvm".

Comgr also supports some environment variables to aid in debugging. These include:

  • AMD_COMGR_SAVE_TEMPS: If this is set, and is not "0", Comgr does not delete temporary files generated during compilation. These files do not appear in the current working directory, but are instead left in a platform-specific temporary directory (typically /tmp on Linux and C:\Temp or the path found in the TEMP environment variable on Windows).
  • AMD_COMGR_REDIRECT_LOGS: If this is not set, or is set to "0", logs are returned to the caller as normal. If this is set to "stdout"/"-" or "stderr", logs are instead redirected to the standard output or error stream, respectively. If this is set to any other value, it is interpreted as a filename which logs should be appended to.
  • AMD_COMGR_EMIT_VERBOSE_LOGS: If this is set, and is not "0", logs will include additional Comgr-specific informational messages.
  • AMD_COMGR_TIME_STATISTICS: If this is set, and is not "0", logs will include additional Comgr-specific timing information for compilation actions.

Versioning

Comgr is versioned according to a major.minor number scheme. The version of the library can be determined dynamically via the amd_comgr_get_version function. The version is not changed due to bug-fixes. The minor version number is incremented for each backwards-compatible change introduced. The major version number is incremented, and the minor version is reset to zero, for each backwards-incompatible change introduced. Information about Comgr changes can be found in the release notes.

ISA Metadata and Versioning

Comgr supports multiple instruction set architectures (ISA) and APIs to query metadata associated with an ISA. The queried metadata follows a semantic versioning scheme e.g. major.minor.patch. The major version changes signifies backward incompatible changes.

  • 1.0.0 : Support for new target feature syntax introduced at AMDGPUUsage. Metadata query for a bare ISA string now returns the supported target features along with other details. A new key for the version is introduced.
  • 0.0.x : Support for querying the metadata for an ISA. The metadata is supplied in a map format with details of target triple, features and resource limits associated with registers and memory addressing. The version key is absent in the Metadata.

Thread Saftey

Comgr strives to be thread-safe when called from multiple threads in the same process. Because of complications from a shared global state in LLVM, to accomplish this Comgr internally implements locking mechanisms around LLVM-based actions.

Although the locks in Comgr can allow independent actions to be safely executed in a multithreaded environment, the user-code must still guard against concurrent method calls which may access any particular Comgr object's state. A Comgr object shared between threads is only safe to use as long as each thread carefully locks out access by any other thread while it uses the shared object.

Coding Standards

Wherever possible, Comgr adheres to the same coding standards as LLVM. Comgr also includes configuration files for clang-format and clang-tidy, which should be used to ensure patches conform.

One notable exception is the test/ subdirectory which prefers camelBack for identifiers rather than CamelCase.

A script at utils/tidy-and-format.sh can be run to help automate the task of ensuring all sources conform to the coding standards. To support the use of this script, any exceptions must be annotated in source comments, as described in the clang-tidy manual.