[llvm-branch-commits] [Flang][OpenMP] Derived type explicit allocatable member mapping (PR #111192)

[Kareem Ergawy via llvm-branch-commits]

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@@ -49,38 +51,95 @@ using DeclareTargetCapturePair =
 // and index data when lowering OpenMP map clauses. Keeps track of the
 // placement of the component in the derived type hierarchy it rests within,
 // alongside the generated mlir::omp::MapInfoOp for the mapped component.
-struct OmpMapMemberIndicesData {
+//
+// As an example of what the contents of this data structure may be like,
+// when provided the following derived type and map of that type:
+//
+// type :: bottom_layer
+//   real(8) :: i2
+//   real(4) :: array_i2(10)
+//   real(4) :: array_j2(10)
+// end type bottom_layer
+//
+// type :: top_layer
+//   real(4) :: i
+//   integer(4) :: array_i(10)
+//   real(4) :: j
+//   type(bottom_layer) :: nested
+//   integer, allocatable :: array_j(:)
+//   integer(4) :: k
+// end type top_layer
+//
+// type(top_layer) :: top_dtype
+//
+// map(tofrom: top_dtype%nested%i2, top_dtype%k, top_dtype%nested%array_i2)
+//
+// We would end up with an OmpMapParentAndMemberData populated like below:
+//
+// memberPlacementIndices:
+//  Vector 1: 3, 0
+//  Vector 2: 5
+//  Vector 3: 3, 1
+//
+// memberMap:
+// Entry 1: omp.map.info for "top_dtype%nested%i2"
+// Entry 2: omp.map.info for "top_dtype%k"
+// Entry 3: omp.map.info for "top_dtype%nested%array_i2"
+//
+// And this OmpMapParentAndMemberData would be accessed via the parent
+// symbol for top_dtype. Other parent derived type instances that have
+// members mapped would have there own OmpMapParentAndMemberData entry
+// accessed via their own symbol.
+struct OmpMapParentAndMemberData {
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ergawy wrote:

Could this be something like this:
```suggestion
struct OmpMapParentAndMemberData {
  struct MemberMappingData {
    llvm::SmallVector<int64_t> placementIndices;
    mlir::omp::MapInfo memberMap;
  };
  
  llvm::SmallVector<MemberMappingData> allMembersData;
};
```

The reason I think this is better is that it ties all the mapping data for a single member in one structure which makes easier to understand what `OmpMapParentAndMemberData` encapsulates.

https://github.com/llvm/llvm-project/pull/111192