[GitHub] [tvm] wrongtest commented on pull request #11181: [LLVM] Fix a possible tbaa issue

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wrongtest commented on PR #11181:
URL: https://github.com/apache/tvm/pull/11181#issuecomment-1113995285

   > Because the value of `last_index_for_tbaa` is cached before this correction is applied, I think it would have incorrect alias information when this correction is applied
   
   Thanks for the notes! After a re look-through, IIUC, I think the "index" for alias info should keep the same element unit for all accesses, so we may not change it either the `last_index` is corrected or not. 
   
   However, before any changes, I find another concern on aliased buffers. since in the new convention, two buffer object (maybe of different datatype) with the same buffer var alias to each other, it may not be safe to use current buffer's dtype as index unit for alias info.
   
   eg1:
   ```python
   # A[16] and B[4] may inferred as NoAlias by tbaa
   A = T.allocate([64], "int8")
   B = T.buffer_decl([16], "int32", data=A.data)
   A[16] = 1   # tag: (A.data, idx=16)  
   B[4] = 1    # tag: (A.data, idx=4)      
   ```
   
   eg2:
   ```python
   # A and B inferred as NoAlias since they have different buffer var
   A = T.allocate([64], "int8")
   B_data = T.address_of(A[4])  # usmp style alias
   B = T.buffer_decl([64], "int8", data=B_data)
   A[7] = 1   # tag: (A.data, idx=7)
   B[3] = 2   # tag: (B.data, idx=3)
   ```


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