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llvm / llvm-project / 95795ab7dc3029e64e0a0a7893b95f4bfab667f1
commit95795ab7dc3029e64e0a0a7893b95f4bfab667f1[log] [tgz]
authorPeter Collingbourne <peter@pcc.me.uk>Mon Apr 28 12:23:42 2025 -0700
committerGitHub <noreply@github.com>Mon Apr 28 12:23:42 2025 -0700
tree6105f223e73711bd22d0ee4cdbf0cdbe1d7b644d
parent9124e963a3bf73fd7430a17535d638601be5630f [diff]
Linker: Remove dropTriviallyDeadConstantArrays().

By calling this function after every link, we introduce quadratic
behavior during full LTO links that primarily affects links involving
large numbers of constant arrays, such as the full LTO part of a
ThinLTO link which will involve large numbers of vtable constants.
Removing this call resulted in a 1.3x speedup in the indexing phase
of a large internal Google binary.

This call was originally introduced to reduce memory consumption during
full LTO (see commit dab999d54f39af3ebb6a23e850dbc9742016fac8), but it
doesn't seem to be the case that this helps any more. I ran 3 stage2
links of clang with full LTO and ThinLTO with and without this change
and measured the max RSS. The results were as follows (all in KB):

```
FullLTO before 22362512 22383524 22387456
         after 22383496 22365356 22364352
ThinLTO before  4391404  4478192  4383468
         after  4399220  4363100  4417688
```

As you can see, any max RSS differences are in the noise.

Reviewers: nikic, teresajohnson

Reviewed By: teresajohnson, nikic

Pull Request: https://github.com/llvm/llvm-project/pull/137081
4 files changed
tree: 6105f223e73711bd22d0ee4cdbf0cdbe1d7b644d
  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. pstl/
  25. runtimes/
  26. third-party/
  27. utils/
  28. .clang-format
  29. .clang-format-ignore
  30. .clang-tidy
  31. .git-blame-ignore-revs
  32. .gitattributes
  33. .gitignore
  34. .mailmap
  35. CODE_OF_CONDUCT.md
  36. CONTRIBUTING.md
  37. LICENSE.TXT
  38. pyproject.toml
  39. README.md
  40. SECURITY.md
README.md

The LLVM Compiler Infrastructure

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Welcome to the LLVM project!

This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

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