[clang][OpenMP] Add OpenMP GPU optimization flag framework (#178914)

This patch series adds a framework of OpenMP GPU optimization flags to
enable more efficient code generation for GPU offloading. The series
consists of three patches:

1. Add negative flag variants (-fno-*) for existing assume options to
allow explicit disabling of optimizations.

2. Add -fopenmp-target-ignore-env-vars flag to indicate that OpenMP
runtime can ignore environment variables during code generation,
enabling optimizations like skipping runtime checks and eliminating
conditional branches.

3. Add -fopenmp-target-fast meta-flag that implies the above
optimization flags. This convenience flag is automatically enabled by
-Ofast and provides a simple interface for aggressive GPU optimizations.

The flags benefit all GPU targets (NVPTX, AMDGPU, Intel GPU) by
providing a standard way to enable common GPU optimization patterns.
Individual flags can be selectively overridden while keeping others
enabled.
3 files changed
tree: 7dbc3a6beab923e1134bc8b248ce245c9ae4b0c7
  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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