[LV] Revert back to use Loop::isLoopInvariant in isPredicatedInst. (#150828)

This partially reverts https://github.com/llvm/llvm-project/pull/140744,
restoring the original TheLoop->isLoopInvariant check instead the more
powerful Legal->isInvariant, which uses SCEV.

This causes a mis-compile, because SCEV can prove that the stored value
is loop-invariant, which in turn converts the store to a uniform store.
But in VPlan, we aren't yet able to determine that the stored value is
loop-invariant, so we extract the last lane, which is incorrect, because
it does not account for the mask of the store.

Restoring the original code is a safe fix and avoids this subtle
divergence.

Fixes https://github.com/llvm/llvm-project/issues/149347.

PR: https://github.com/llvm/llvm-project/pull/150828
2 files changed
tree: 997e59742b976061efb4c3ed5ccf40bf8f2c13cb
  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. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-format-ignore
  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
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