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chromium / external / github.com / llvm / llvm-project / 281028e37ca6c97c62ba68cd43eda2ff95bc70c4
commit281028e37ca6c97c62ba68cd43eda2ff95bc70c4[log] [tgz]
authorRyotaro Kasuga <kasuga.ryotaro@fujitsu.com>Fri Mar 21 12:42:49 2025
committerGitHub <noreply@github.com>Fri Mar 21 12:42:49 2025
tree03830d3586dabda28a7c315cc625126eb93aead0
parentea03bdee7081f25c652d581e274b10cb7c552357 [diff]
[LoopInterchange] Prevent from undoing its own transformation (#127473)

LoopInterchange uses the bubble-sort fashion algorithm to sort the loops
in a loop nest. For two loops `A` and `B`, it calls `isProfitable(A, B)`
to determine whether these loops should be exchanged. The result of
`isProfitable(A, B)` should be conservative, that is, it should return
true only when we are sure exchanging `A` and `B` will improve
performance. If it's not conservative enough, it's possible that a
subsequent `isProfitable(B, A)` will also return true, in which case
LoopInterchange will undo its previous transformation. To avoid such
cases, `isProfitable(B, A)` must not return true if `isProfitable(A, B)`
returned true in the past. However, the current implementation can be in
such a situation. This patch resolves it by correcting the handling of
two loops that have the same cache cost.

This resolve the problem mentioned in
https://github.com/llvm/llvm-project/pull/118267#issuecomment-2510759354.
2 files changed
tree: 03830d3586dabda28a7c315cc625126eb93aead0
  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-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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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.

The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.

C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

Consult the Getting Started with LLVM page for information on building and running LLVM.

For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

Getting in touch

Join the LLVM Discourse forums, Discord chat, LLVM Office Hours or Regular sync-ups.

The LLVM project has adopted a code of conduct for participants to all modes of communication within the project.