[DebugInfo] Fully implement DWARF issue 180201.1 (#149226)

Finish making LLVM's implementation of `DW_LNCT_LLVM_source` conform to
the final accepted version of `DW_LNCT_source` from
https://dwarfstd.org/issues/180201.1.html

This is effectively a continuation of a few commits which have moved in
this direction already, including:

* c9cb4fc761cd7 [DebugInfo] Store optional DIFile::Source as pointer
* 87e22bdd2bd6d Allow for mixing source/no-source DIFiles in one CU

This patch:

* Teaches LLParser that there is a distinction between an empty and an
absent "source:" field on DIFile.
* Makes printing the "source:" field in AsmWriter conditional on it
being present, instead of being conditional on it being non-empty.
* Teaches MC to map an empty-but-present source field to "\n" (which is
ambiguous, making the source strings "" and "\n" indistinguishable, but
that's what the DWARF issue specifies).

Add a test for round-tripping an empty source field through
assembler/bitcode.

Extend the test for the actual DWARF generation so it covers all of the
cases (absent, present-but-empty,
present-and-ambiguously-single-newline, present).
5 files changed
tree: 96ec6ecff0bf08f90409b0d0f82762a9570bc5b6
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libunwind/
  16. lld/
  17. lldb/
  18. llvm/
  19. llvm-libgcc/
  20. mlir/
  21. offload/
  22. openmp/
  23. polly/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-format-ignore
  29. .clang-tidy
  30. .git-blame-ignore-revs
  31. .gitattributes
  32. .gitignore
  33. .mailmap
  34. CODE_OF_CONDUCT.md
  35. CONTRIBUTING.md
  36. LICENSE.TXT
  37. pyproject.toml
  38. README.md
  39. SECURITY.md
README.md

The LLVM Compiler Infrastructure

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