[CIR] Fix spurious MemRead on pure pointer-arithmetic ops (#185154)

Remove incorrect [MemRead] annotations from seven CIR ops that only
perform pointer arithmetic, and add the Pure trait where missing.

- VTableGetVPtrOp computes the address of the vptr slot within an
object. Since the vptr is always at offset zero, this is a bitcast —
confirmed by the lowering which does replaceOp(op, srcVal). No memory
access.

- VTableGetVirtualFnAddrOp takes an already-loaded !cir.vptr value and
an index, computes the address of the nth vtable entry. Lowers to a
GEPOp. No memory access.

- VTableGetTypeInfoOp takes an already-loaded !cir.vptr value, computes
the address of the type_info entry at a known ABI offset. Pointer
arithmetic only. No memory access.

- GetMemberOp computes the address of a struct/class member given a base
pointer and a constant index. Lowers to GEPOp (struct/class) or
BitcastOp (union). No memory access.

- GetRuntimeMemberOp computes a member address using a runtime
pointer-to-data-member value. Lowers to CastOp + PtrStrideOp (byte-level
pointer arithmetic). No memory access.

- BaseClassAddrOp computes the base class address from a derived class
pointer using a byte offset. Lowers to GEPOp/BitcastOp with a null check
when needed. No memory access.

- DerivedClassAddrOp computes the derived class address from a base
class pointer using a negative byte offset. Lowers to GEPOp with a null
check when needed. No memory access.

In all cases, the actual memory reads are performed by separate cir.load
ops that follow these address computations.
2 files changed
tree: a5b83523425aaa09ce7783ee150a2c538030401f
  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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