[PATCH] D145803: [clang][DebugInfo] Emit DW_AT_type of preferred name if available

[Michael Buch via Phabricator via cfe-commits]

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Yet another alternative for emitting preferred_names.

Makes the attribute introduced in https://reviews.llvm.org/D145077 redundant. Also doesn't require any changes to LLDB (making https://reviews.llvm.org/D145078 redundant, which got a bit hairy)


aprantl added a comment.

This seems to be a much simpler implementation that just automatically works. I think I'd prefer that over adding new DWARF attributes.


Michael137 added a comment.

- Add test


Michael137 added a comment.

- Update commit message


[clang][DebugInfo] Emit DW_AT_type of preferred name if available

With this patch, whenever we emit a `DW_AT_type` for some declaration
and the type is a template class with a `clang::PreferredNameAttr`, we
will emit the typedef that the attribute refers to instead. I.e.,

  0x123 DW_TAG_variable
  DW_AT_name "var"
  DW_AT_type (0x123 "basic_string<char>")
  
  0x124 DW_TAG_structure_type
  DW_AT_name "basic_string<char>"

...becomes

  0x123 DW_TAG_variable
  DW_AT_name "var"
  DW_AT_type (0x124 "std::string")
  
  0x124 DW_TAG_structure_type
  DW_AT_name "basic_string<char>"
  
  0x125 DW_TAG_typedef
  DW_AT_name "std::string"
  DW_AT_type (0x124 "basic_string<char>")

For now we keep this behind LLDB tuning.

**Testing**

- Added clang unit-test
- `check-llvm`, `check-clang` pass
- Confirmed that this change correctly repoints

`basic_string` references in some of my test programs.

- Will add follow-up LLDB API tests


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145803

Files:
  clang/lib/CodeGen/CGDebugInfo.cpp
  clang/lib/CodeGen/CGDebugInfo.h
  clang/test/CodeGen/preferred_name.cpp

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