[PATCH] D79592: [DebugInfo] support for DW_AT_data_location in llvm

[Alok Kumar Sharma via Phabricator via llvm-commits]

alok added a comment.

In D79592#2025853 <https://reviews.llvm.org/D79592#2025853>, @aprantl wrote:

> Why is the data location a part of the type and not something dynamically bound via dbg.value or something similar?
>
> What's an example for what a typical data location expression?


Dynamic arrays are represented by two things

- allocated space
- descriptor which describes the array bounds (always) and allocated space (not always)

DW_AT_location attached to DW_TAG_variable denotes descriptor, which is used by bounds (using DW_OP_push_object_address). Since DW_AT_location denotes descriptor, DW_AT_data_location is used to denote allocated space. DWARF has attached that to DW_TAG_array_type.
In cases when descriptor also has a pointer to allocated space (as in case of gfortran), DW_AT_data_location can also be described by DW_OP_push_object_address and offset where the pointer to allocated space is. In cases when descriptor does not have the pointer to allocated space (as in case of flang), DW_AT_data_location can be represented by DIE reference which denotes an artificial variable which has the data pointer (dbg.declare in IR).
Please let me know if you need more information.


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