[OpenCL] Add clang internal extension __cl_clang_function_scope_local_variables  (#176726)

OpenCL spec restricts that variable in local address space can only be
declared at kernel function scope.
Add a Clang internal extension __cl_clang_function_scope_local_variables
to lift the restriction.

To expose static local allocations at kernel scope, targets can either
force-inline non-kernel functions that declare local memory or pass a
kernel-allocated local buffer to those functions via an implicit argument.

Motivation: support local memory allocation in libclc's implementation
of work-group collective built-ins, see example at:
https://github.com/intel/llvm/blob/41455e305117/libclc/libspirv/lib/amdgcn-amdhsa/group/collectives_helpers.ll
https://github.com/intel/llvm/blob/41455e305117/libclc/libspirv/lib/amdgcn-amdhsa/group/collectives.cl#L182

Right now this is a Clang-only OpenCL extension intended for compiling
OpenCL libraries with Clang. It could be proposed as a standard OpenCL
extension in the future.
6 files changed
tree: e6c7b7486f1cf44ce6772997faa38d80bc6cd17c
  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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