[AArch64][SME][SDAG] Add basic support for exception handling (#159363)

This patch adds basic support for exception handling to SelectionDAG for
ZT0, ZA, and agnostic ZA state. This works based on the following
assumptions:

- To throw an exception requires calling into the runtime
  * The which will be a private ZA call (that commits the lazy save)
- Therefore, as noted in https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#exceptions
we will always enter the EH block with PSTATE.ZA=0 and TPIDR2_EL0=null,
so we can emit a restore of ZA/ZT0.

Note: This patch does not handle all cases yet. Currently, there is no
support for committing agnostic ZA state before `invoke`s, regardless of
whether the callee is also agnostic (to ensure ZA state is saved on all
normal returns).
2 files changed
tree: 3dbb75a2e8da23af6f9c5d6c25098c8e059e00b2
  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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