| Integrated Distributed ThinLTO (DTLTO) |
| ====================================== |
| |
| Integrated Distributed ThinLTO (DTLTO) enables the distribution of backend |
| ThinLTO compilations via external distribution systems, such as Incredibuild, |
| during the traditional link step. |
| |
| The implementation is documented here: https://llvm.org/docs/DTLTO.html. |
| |
| Currently, DTLTO is only supported in ELF and COFF LLD. |
| |
| ELF LLD |
| ------- |
| |
| The command-line interface is as follows: |
| |
| - ``--thinlto-distributor=<path>`` |
| Specifies the file to execute as the distributor process. If specified, |
| ThinLTO backend compilations will be distributed. |
| |
| - ``--thinlto-remote-compiler=<path>`` |
| Specifies the path to the compiler that the distributor process will use for |
| backend compilations. The compiler invoked must match the version of LLD. |
| |
| - ``--thinlto-distributor-arg=<arg>`` |
| Specifies ``<arg>`` on the command line when invoking the distributor. |
| Can be specified multiple times. |
| |
| - ``--thinlto-remote-compiler-arg=<arg>`` |
| Appends ``<arg>`` to the remote compiler's command line. |
| Can be specified multiple times. |
| |
| Options that introduce extra input/output files may cause miscompilation if |
| the distribution system does not automatically handle pushing/fetching them to |
| remote nodes. In such cases, configure the distributor - possibly using |
| ``--thinlto-distributor-arg=`` - to manage these dependencies. See the |
| distributor documentation for details. |
| |
| Some LLD LTO options (e.g., ``--lto-sample-profile=<file>``) are supported. |
| Currently, other options are silently accepted but do not have the intended |
| effect. Support for such options will be expanded in the future. |
| |
| COFF LLD |
| -------- |
| |
| The command-line interface is as follows: |
| |
| - ``/thinlto-distributor:<path>`` |
| Specifies the file to execute as the distributor process. If specified, |
| ThinLTO backend compilations will be distributed. |
| |
| - ``/thinlto-remote-compiler:<path>`` |
| Specifies the path to the compiler that the distributor process will use for |
| backend compilations. The compiler invoked must match the version of LLD. |
| |
| - ``/thinlto-distributor-arg:<arg>`` |
| Specifies ``<arg>`` on the command line when invoking the distributor. |
| Can be specified multiple times. |
| |
| - ``/thinlto-remote-compiler-arg:<arg>`` |
| Appends ``<arg>`` to the remote compiler's command line. |
| Can be specified multiple times. |
| |
| Options that introduce extra input/output files may cause miscompilation if |
| the distribution system does not automatically handle pushing/fetching them to |
| remote nodes. In such cases, configure the distributor - possibly using |
| ``/thinlto-distributor-arg:`` - to manage these dependencies. See the |
| distributor documentation for details. |
| |
| Some LLD LTO options (e.g., ``/lto-sample-profile:<file>``) are supported. |
| Currently, other options are silently accepted but do not have the intended |
| effect. Support for such options could be expanded in the future. |
| |
| Currently, there is no DTLTO command line interface supplied for ``clang-cl``, |
| as users are expected to invoke LLD directly. |
