[CGP][PAC] Flip PHI and blends when all immediate modifiers are the same

GVN PRE, SimplifyCFG and possibly other passes may hoist the call to
`@llvm.ptrauth.blend` intrinsic, introducing multiple duplicate call
instructions hidden behind a PHI node. This prevents the instruction
selector from generating safer code by absorbing the address and
immediate modifiers into separate operands of AUT, PAC, etc. pseudo
instruction.

This patch makes CodeGenPrepare pass detect when discriminator is
computed as a PHI node with all incoming values being blends with the
same immediate modifier. Each such discriminator value is replaced by a
single blend, whose address argument is computed by a PHI node.
2 files changed
tree: e8466c1af3d0289744da33833d300ef034a401c6
  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
README.md

The LLVM Compiler Infrastructure

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