[all-commits] [llvm/llvm-project] 3b4e79: [DTLTO][LLD][ELF] Add support for Integrated Distr...

[bd1976bris via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3b4e79398de5e6f5c4603c40d279a95dd57d0950
      https://github.com/llvm/llvm-project/commit/3b4e79398de5e6f5c4603c40d279a95dd57d0950
  Author: bd1976bris <bd1976llvm at gmail.com>
  Date:   2025-07-02 (Wed, 02 Jul 2025)

  Changed paths:
    M cross-project-tests/CMakeLists.txt
    A cross-project-tests/dtlto/README.md
    A cross-project-tests/dtlto/ld-dtlto.c
    A cross-project-tests/dtlto/lit.local.cfg
    M lld/ELF/Config.h
    M lld/ELF/Driver.cpp
    M lld/ELF/LTO.cpp
    M lld/ELF/Options.td
    A lld/docs/DTLTO.rst
    M lld/docs/index.rst
    A lld/test/ELF/dtlto/files.test
    A lld/test/ELF/dtlto/options.test
    A lld/test/ELF/dtlto/partitions.test
    M lld/test/lit.cfg.py

  Log Message:
  -----------
  [DTLTO][LLD][ELF] Add support for Integrated Distributed ThinLTO (#142757)

This patch introduces support for Integrated Distributed ThinLTO (DTLTO)
in ELF LLD.

DTLTO enables the distribution of ThinLTO backend compilations via
external distribution systems, such as Incredibuild, during the
traditional link step: https://llvm.org/docs/DTLTO.html.

It is expected that users will invoke DTLTO through the compiler driver
(e.g., Clang) rather than calling LLD directly. A Clang-side interface
for DTLTO will be added in a follow-up patch.

Note: Bitcode members of archives (thin or non-thin) are not currently
supported. This will be addressed in a future change. As a consequence
of this lack of support, this patch is not sufficient to allow for
self-hosting an LLVM build with DTLTO. Theoretically,
--start-lib/--end-lib could be used instead of archives in a self-host
build. However, it's unclear how --start-lib/--end-lib can be easily
used with the LLVM build system.

Testing:
- ELF LLD `lit` test coverage has been added, using a mock distributor
  to avoid requiring Clang.
- Cross-project `lit` tests cover integration with Clang.

For the design discussion of the DTLTO feature, see: #126654.



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