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1Integrated Distributed ThinLTO (DTLTO)2======================================3 4Integrated Distributed ThinLTO (DTLTO) enables the distribution of backend5ThinLTO compilations via external distribution systems, such as Incredibuild,6during the traditional link step.7 8The implementation is documented here: https://llvm.org/docs/DTLTO.html.9 10Currently, DTLTO is only supported in ELF and COFF LLD.11 12ELF LLD13-------14 15The command-line interface is as follows:16 17- ``--thinlto-distributor=<path>``18 Specifies the file to execute as the distributor process. If specified,19 ThinLTO backend compilations will be distributed.20 21- ``--thinlto-remote-compiler=<path>``22 Specifies the path to the compiler that the distributor process will use for23 backend compilations. The compiler invoked must match the version of LLD.24 25- ``--thinlto-distributor-arg=<arg>``26 Specifies ``<arg>`` on the command line when invoking the distributor.27 Can be specified multiple times.28 29- ``--thinlto-remote-compiler-prepend-arg=<arg>``30 Prepends ``<arg>`` to the remote compiler's command line.31 Can be specified multiple times.32 33- ``--thinlto-remote-compiler-arg=<arg>``34 Appends ``<arg>`` to the remote compiler's command line.35 Can be specified multiple times.36 37 Options that introduce extra input/output files may cause miscompilation if38 the distribution system does not automatically handle pushing/fetching them to39 remote nodes. In such cases, configure the distributor - possibly using40 ``--thinlto-distributor-arg=`` - to manage these dependencies. See the41 distributor documentation for details.42 43Some LLD LTO options (e.g., ``--lto-sample-profile=<file>``) are supported.44Currently, other options are silently accepted but do not have the intended45effect. Support for such options will be expanded in the future.46 47COFF LLD48--------49 50The command-line interface is as follows:51 52- ``/thinlto-distributor:<path>``53 Specifies the file to execute as the distributor process. If specified,54 ThinLTO backend compilations will be distributed.55 56- ``/thinlto-remote-compiler:<path>``57 Specifies the path to the compiler that the distributor process will use for58 backend compilations. The compiler invoked must match the version of LLD.59 60- ``/thinlto-distributor-arg:<arg>``61 Specifies ``<arg>`` on the command line when invoking the distributor.62 Can be specified multiple times.63 64- ``/thinlto-remote-compiler-prepend-arg:<arg>``65 Prepends ``<arg>`` to the remote compiler's command line.66 Can be specified multiple times.67 68- ``/thinlto-remote-compiler-arg:<arg>``69 Appends ``<arg>`` to the remote compiler's command line.70 Can be specified multiple times.71 72 Options that introduce extra input/output files may cause miscompilation if73 the distribution system does not automatically handle pushing/fetching them to74 remote nodes. In such cases, configure the distributor - possibly using75 ``/thinlto-distributor-arg:`` - to manage these dependencies. See the76 distributor documentation for details.77 78Some LLD LTO options (e.g., ``/lto-sample-profile:<file>``) are supported.79Currently, other options are silently accepted but do not have the intended80effect. Support for such options could be expanded in the future.81 82Currently, there is no DTLTO command line interface supplied for ``clang-cl``,83as users are expected to invoke LLD directly.84