[all-commits] [llvm/llvm-project] bc4bed: [mlir][debug] Handle DIImportedEntity. (#103055)

[Abid Qadeer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bc4bedd5ed2c8d9f1a648c72d38e17361aff8a30
      https://github.com/llvm/llvm-project/commit/bc4bedd5ed2c8d9f1a648c72d38e17361aff8a30
  Author: Abid Qadeer <haqadeer at amd.com>
  Date:   2024-08-27 (Tue, 27 Aug 2024)

  Changed paths:
    M flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
    M mlir/include/mlir-c/Dialect/LLVM.h
    M mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td
    M mlir/lib/CAPI/Dialect/LLVM.cpp
    M mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp
    M mlir/lib/Dialect/LLVMIR/Transforms/DIScopeForLLVMFuncOp.cpp
    M mlir/lib/Target/LLVMIR/DebugImporter.cpp
    M mlir/lib/Target/LLVMIR/DebugImporter.h
    M mlir/lib/Target/LLVMIR/DebugTranslation.cpp
    M mlir/lib/Target/LLVMIR/DebugTranslation.h
    M mlir/test/CAPI/llvm.c
    M mlir/test/Target/LLVMIR/Import/debug-info.ll
    M mlir/test/Target/LLVMIR/llvmir-debug.mlir

  Log Message:
  -----------
  [mlir][debug] Handle DIImportedEntity. (#103055)

The `DIImporedEntity` can be used to represent imported entities like
C++'s namespace with using directive or fortran's moudule with use
statement.

This PR adds `DIImportedEntityAttr` and 2-way translation from
`DIImportedEntity` to `DIImportedEntityAttr` and vice versa.

When an entity is imported in a function, the `retainedNodes` field of
the `DISubprogram` contains all the imported nodes. See the C++ code and
the LLVM IR below.

```
void test() {
    using namespace n1;
 ...
}

!2 = !DINamespace(name: "n1", scope: null)
!16 = distinct !DISubprogram(name: "test", ..., retainedNodes: !19) !19 = !{!20}
!20 = !DIImportedEntity(tag: DW_TAG_imported_module, scope: !16, entity: !2 ...)
```

This PR makes sure that the translation from mlir to `retainedNodes`
field happens correctly both ways.

To side step the cyclic dependency between `DISubprogramAttr` and `DIImportedEntityAttr`,
we have decided to not have `scope` field in the `DIImportedEntityAttr` and it is inferred
from the entity which hold the list of `DIImportedEntityAttr`. A `retainedNodes` field has been
added in the `DISubprogramAttr` which contains the list of `DIImportedEntityAttr` for that
function.

This PR currently does not handle entities imported in a global scope
but that should be easy to handle in a subsequent PR.



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