[lld][WebAssembly] Preserve segment linking flags in --relocatable output (#210747)

`OutputSegment::addInputSegment` copied each input chunk's alignment but
never its flags, so a relocatable link serialized `flags=0` for every
data segment and dropped `RETAIN` and `STRINGS`. Losing `RETAIN` let the
final default `--gc-sections` link discard runtime-registered sections
such as Swift's `swift5_*` metadata, corrupting the program. This unions
each input segment's flags into the output segment's `linkingFlags` and
adds a `lld/test/wasm` test covering `RETAIN`, `STRINGS`, and flag
accumulation across coalesced segments.

Resolves
https://github.com/swiftlang/swift-package-manager/issues/10314.

GitOrigin-RevId: 162d9f09299d3951d7c73e6aa00f2e2bac459e26
2 files changed
tree: d3da1b58f9a4d797e883283e7889df4b322ea0bb
  1. cmake/
  2. COFF/
  3. Common/
  4. docs/
  5. ELF/
  6. include/
  7. MachO/
  8. MinGW/
  9. test/
  10. tools/
  11. unittests/
  12. utils/
  13. wasm/
  14. .clang-format
  15. .clang-tidy
  16. .gitignore
  17. CMakeLists.txt
  18. LICENSE.TXT
  19. Maintainers.md
  20. README.md
README.md

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.