[acc] acc.loop verifier now requires parallelism determination flag (#143720)

The OpenACC specification for `acc loop` describe that a loop's
parallelism determination mode is either auto, independent, or seq. The
rules are as follows.
- As per OpenACC 3.3 standard section 2.9.6 independent clause: A loop
construct with no auto or seq clause is treated as if it has the
independent clause when it is an orphaned loop construct or its parent
compute construct is a parallel construct.
- As per OpenACC 3.3 standard section 2.9.7 auto clause: When the parent
compute construct is a kernels construct, a loop construct with no
independent or seq clause is treated as if it has the auto clause.
- Additionally, loops marked with gang, worker, or vector are not
guaranteed to be parallel. Specifically noted in 2.9.7 auto clause: If
not, or if it is unable to make a determination, it must treat the auto
clause as if it is a seq clause, and it must ignore any gang, worker, or
vector clauses on the loop construct.

The verifier for `acc.loop` was updated to enforce this marking because
the context in which a loop appears is not trivially determined once IR
transformations begin. For example, orphaned loops are implicitly
`independent`, but after inlining into an `acc.kernels` region they
would be implicitly considered `auto`. Thus now the verifier requires
that a frontend specifically generates acc dialect with this marking
since it knows the context.
5 files changed
tree: 4ffd13aff518fe3df1b5496024bee6348157939f
  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-format-ignore
  30. .clang-tidy
  31. .git-blame-ignore-revs
  32. .gitattributes
  33. .gitignore
  34. .mailmap
  35. CODE_OF_CONDUCT.md
  36. CONTRIBUTING.md
  37. LICENSE.TXT
  38. pyproject.toml
  39. README.md
  40. SECURITY.md
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