[all-commits] [llvm/llvm-project] 673476: [DTLTO][LLD][ELF] Support bitcode members of thin ...

[bd1976bris via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 673476d96bed306be6ed81a8174f481a9a4b2934
      https://github.com/llvm/llvm-project/commit/673476d96bed306be6ed81a8174f481a9a4b2934
  Author: bd1976bris <Ben.Dunbobbin at sony.com>
  Date:   2025-08-01 (Fri, 01 Aug 2025)

  Changed paths:
    M cross-project-tests/CMakeLists.txt
    A cross-project-tests/dtlto/ld-archive-thin.test
    M cross-project-tests/lit.cfg.py
    M lld/ELF/InputFiles.cpp
    A lld/test/ELF/dtlto/archive-thin.test

  Log Message:
  -----------
  [DTLTO][LLD][ELF] Support bitcode members of thin archives (#149425)

This patch adds support for bitcode members of thin archives to DTLTO
(https://llvm.org/docs/DTLTO.html) in ELF LLD.

For DTLTO, bitcode identifiers must be valid paths to bitcode files on
disk. Clang does not support archive inputs for ThinLTO backend
compilations. This patch adjusts the identifier for bitcode members of
thin archives in DTLTO links so that it is the path to the member file
on disk, allowing such members to be supported in DTLTO.

This patch is sufficient to allow for self-hosting an LLVM build with
DTLTO when thin archives are used.

Note: Bitcode members of non-thin archives remain unsupported. This will
be addressed in a future change.

Testing:
- LLD lit test coverage has been added to check that the identifier is
adjusted appropriately.
- A cross-project lit test has been added to show that a DTLTO link can
succeed when linking bitcode members of thin archives.

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



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