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llvm / llvm-project / 89d86b626cb29fbd7b476ea6f082256691444ad5
commit89d86b626cb29fbd7b476ea6f082256691444ad5[log] [tgz]
authorJessica Del <50999226+OutOfCache@users.noreply.github.com>Tue Sep 09 16:24:52 2025 +0200
committerGitHub <noreply@github.com>Tue Sep 09 16:24:52 2025 +0200
treef12ca06dacad3f94f758f050b028c488e85dda36
parent4aa59f550a95803e876001e9f416af207d7936a8 [diff]
SimplifyCFG: Enable switch replacements in more cases (#156477)

In some cases, we can replace a switch with simpler instructions or a
lookup table.
For instance, if every case results in the same value, we can simply
replace the switch
with that single value.

However, lookup tables are not always supported. 
Targets, function attributes and compiler options can deactivate lookup
table creation.
Currently, even simpler switch replacements like the single value
optimization do not
get applied, because we only enable these transformations if lookup
tables are enabled.

This PR enables the other kinds of replacements, even if lookup tables
are not supported.
First, it checks if the potential replacements are lookup tables.
If they are, then check if lookup tables are supported and whether to
continue.
If they are not, then we can apply the other transformations.

Originally, lookup table creation was delayed until late stages of the
compilation pipeline, because
it can result in difficult-to-analyze code and prevent other
optimizations.
As a side effect of this change, we can also enable the simpler
optimizations much earlier in the
compilation process.
2 files changed
tree: f12ca06dacad3f94f758f050b028c488e85dda36
  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. libsycl/
  16. libunwind/
  17. lld/
  18. lldb/
  19. llvm/
  20. llvm-libgcc/
  21. mlir/
  22. offload/
  23. openmp/
  24. orc-rt/
  25. polly/
  26. runtimes/
  27. third-party/
  28. utils/
  29. .clang-format
  30. .clang-format-ignore
  31. .clang-tidy
  32. .git-blame-ignore-revs
  33. .gitattributes
  34. .gitignore
  35. .mailmap
  36. CODE_OF_CONDUCT.md
  37. CONTRIBUTING.md
  38. LICENSE.TXT
  39. pyproject.toml
  40. README.md
  41. SECURITY.md
README.md

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