[SLP] Normalize copyable operand order via majority voting

When building operands for entries with copyable elements, non-copyable
lanes of commutative ops may have inconsistent operand order (e.g. some
lanes have load,add while others have add,load). This prevents
VLOperands::reorder() from grouping consecutive loads on one side,
degrading downstream vectorization.
Add majority-voting normalization during buildOperands: track the
(ValueID, ValueID) pair frequency across non-copyable lanes and swap
any lane whose operand types are the exact inverse of the most common
pattern. This makes operand order consistent, enabling better load
grouping.
This is part 1 of #189181.

Reviewers: RKSimon, hiraditya

Pull Request: https://github.com/llvm/llvm-project/pull/191631
5 files changed
tree: e4037a290b2955b380210f1479b05ef14ed56bdc
  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
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