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llvm / llvm-project / 6da3361f504495cef71caa4de4297234b6ea7fc7
commit6da3361f504495cef71caa4de4297234b6ea7fc7[log] [tgz]
authorNikita Popov <npopov@redhat.com>Wed Aug 14 09:37:38 2024 +0200
committerGitHub <noreply@github.com>Wed Aug 14 09:37:38 2024 +0200
treed36749532614d52e1ebc635ab6698f1ca540f392
parent241f9e7492dae1920778ef4fe72db6073b6275b1 [diff]
[SCEV] Look through multiply in computeConstantDifference() (#103051)

Inside computeConstantDifference(), handle the case where both sides are
of the form `C * %x`, in which case we can strip off the common
multiplication (as long as we remember to multiply by it for the
following difference calculation).

There is an obvious alternative implementation here, which would be to
directly decompose multiplies inside the "Multiplicity" accumulation.
This does work, but I've found this to be both significantly slower
(because everything has to work on APInt) and more complex in
implementation (e.g. because we now need to match back the new More/Less
with an arbitrary factor) without providing more power in practice. As
such, I went for the simpler variant here.

This is the last step to make computeConstantDifference() sufficiently
powerful to replace existing uses of
`cast<SCEVConstant>(getMinusSCEV())` with it.
2 files changed
tree: d36749532614d52e1ebc635ab6698f1ca540f392
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. libc/
  11. libclc/
  12. libcxx/
  13. libcxxabi/
  14. libunwind/
  15. lld/
  16. lldb/
  17. llvm/
  18. llvm-libgcc/
  19. mlir/
  20. offload/
  21. openmp/
  22. polly/
  23. pstl/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-tidy
  29. .git-blame-ignore-revs
  30. .gitattributes
  31. .gitignore
  32. .mailmap
  33. CODE_OF_CONDUCT.md
  34. CONTRIBUTING.md
  35. LICENSE.TXT
  36. pyproject.toml
  37. README.md
  38. SECURITY.md
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