9c0c98ed37
As part of the WebAssembly support work https://github.com/llvm/llvm-project/pull/85566 The README.txt is a bit odd since it only lists issues and problems without talking about what works. It’s also hard to read on the GitHub web view. - Convert to Markdown and linking to the command docs https://llvm.org/docs/CommandGuide/llvm-debuginfo-analyzer - Rename some left 'elf reader' to 'DWARF reader'.
171 lines
6.7 KiB
Markdown
171 lines
6.7 KiB
Markdown
# `llvm-debuginfo-analyzer`
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These are the notes collected during the development, review and test.
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They describe limitations, known issues and future work.
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### Remove the use of macros in ``LVReader.h`` that describe the ``bumpallocators``.
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**[D137933](https://reviews.llvm.org/D137933#inline-1389904)**
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Use a standard (or LLVM) ``map`` with ``typeinfo`` (would need a specialization
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to expose equality and hasher) for the allocators and the creation
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functions could be a function template.
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### Use a **lit test** instead of a **unit test** for the **logical readers**.
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**[D125783](https://reviews.llvm.org/D125783#inline-1324376)**
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As the ``DebugInfoLogicalView`` library is sufficiently exposed via the
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``llvm-debuginfo-analyzer`` tool, follow the LLVM general approach and
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use ``lit`` tests to validate the **logical readers**.
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Convert the ``unitests``:
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```
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llvm-project/llvm/unittests/DebugInfo/LogicalView/CodeViewReaderTest.cpp
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llvm-project/llvm/unittests/DebugInfo/LogicalView/DWARFReaderTest.cpp
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```
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into ``lit`` tests:
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```
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llvm-project/llvm/test/DebugInfo/LogicalView/CodeViewReader.test
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llvm-project/llvm/test/DebugInfo/LogicalView/DWARFReader.test
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```
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### Eliminate calls to ``getInputFileDirectory()`` in the ``unittests``.
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**[D125783](https://reviews.llvm.org/D125783#inline-1324359)**
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Rewrite the unittests ``ReaderTest`` and ``CodeViewReaderTest`` to eliminate
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the call:
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```
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getInputFileDirectory()
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```
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as use of that call is discouraged.
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### Fix mismatch between ``%d/%x`` format strings and ``uint64_t`` type.
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**[D137400](https://reviews.llvm.org/D137400) / [58758](https://github.com/llvm/llvm-project/issues/58758)**
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Incorrect printing of ``uint64_t`` on ``32-bit`` platforms.
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Add the ``PRIx64`` specifier to the printing code (``format()``).
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### Remove ``LVScope::Children`` container.
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**[D137933](https://reviews.llvm.org/D137933#inline-1373902)**
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Use a **chaining iterator** over the other containers rather than keep a
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separate container ``Children`` that mirrors their contents.
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### Use ``TableGen`` for command line options.
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**[D125777](https://reviews.llvm.org/D125777#inline-1291801)**
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The current trend is to use ``TableGen`` for command-line options in tools.
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Change command line options to use ``tablegen`` as many other LLVM tools.
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### ``LVDoubleMap`` to return ``optional<ValueType>`` instead of ``null pointer``.
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**[D125783](https://reviews.llvm.org/D125783#inline-1294164)**
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The more idiomatic LLVM way to handle this would be to have ``find``
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return ``Optional<ValueType>``.
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### Pass references instead of pointers (**Comparison functions**).
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**[D125782](https://reviews.llvm.org/D125782#inline-1293920)**
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In the **comparison functions**, pass references instead of pointers (when
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pointers cannot be null).
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### Use ``StringMap`` where possible.
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**[D125783](https://reviews.llvm.org/D125783#inline-1294211)**
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LLVM has a ``StringMap`` class that is advertised as more efficient than
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``std::map<std::string, ValueType>``. Mainly it does fewer allocations
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because the key is not a ``std::string``.
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Replace the use of ``std::map<std::string, ValueType>`` with ``StringMap``.
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One specific case is the ``LVSymbolNames`` definitions.
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### Calculate unique offset for CodeView elements.
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In order to have the same logical functionality as the DWARF reader, such
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as:
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* find scopes contribution to debug info
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* sort by its physical location
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The logical elements must have an unique offset (similar like the DWARF
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``DIE`` offset).
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### Move ``initializeFileAndStringTables`` to the CodeView Library.
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There is some code in the CodeView reader that was extracted/adapted
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from ``tools/llvm-readobj/COFFDumper.cpp`` that can be moved to the CodeView
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library.
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We had a similar case with code shared with ``llvm-pdbutil`` that was moved
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to the PDB library: **[D122226](https://reviews.llvm.org/D122226)**
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### Move ``getSymbolKindName`` and ``formatRegisterId`` to the CodeView Library.
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There is some code in the CodeView reader that was extracted/adapted
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from ``lib/DebugInfo/CodeView/SymbolDumper.cpp`` that can be used.
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### Use of ``std::unordered_set`` instead of ``std::set``.
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**[D125784](https://reviews.llvm.org/D125784#inline-1221421)**
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Replace the ``std::set`` usage for ``DeducedScopes``, ``UnresolvedScopes`` and
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``IdentifiedNamespaces`` with ``std::unordered_set`` and get the benefit
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of the O(1) while inserting/searching, as the order is not important.
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### Optimize ``LVNamespaceDeduction::find`` funtion.
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**[D125784](https://reviews.llvm.org/D125784#inline-1296195)**
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Optimize the ``find`` method to use the proposed code:
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```
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LVStringRefs::iterator Iter = std::find_if(Components.begin(), Components.end(),
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[](StringRef Name) {
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return IdentifiedNamespaces.find(Name) == IdentifiedNamespaces.end();
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});
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LVStringRefs::size_type FirstNonNamespace = std::distance(Components.begin(), Iter);
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```
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### Move all the printing support to a common module.
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Factor out printing functionality from the logical elements into a
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common module.
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### Refactor ``LVBinaryReader::processLines``.
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**[D125783](https://reviews.llvm.org/D125783#inline-1246155) /
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[D137156](https://reviews.llvm.org/D137156)**
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During the traversal of the debug information sections, we created the
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logical lines representing the **disassembled instructions** from the **text
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section** and the logical lines representing the **line records** from the
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**debug line** section. Using the ranges associated with the logical scopes,
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we will allocate those logical lines to their logical scopes.
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Consider the case when any of those lines become orphans, causing
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incorrect scope parent for disassembly or line records.
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### Add support for ``-ffunction-sections``.
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**[D125783](https://reviews.llvm.org/D125783#inline-1295012)**
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Only linked executables are handled. It does not support relocatable
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files compiled with ``-ffunction-sections``.
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### Add support for DWARF v5 `.debug_names` section / CodeView public symbols stream.
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**[D125783](https://reviews.llvm.org/D125783#inline-1294142)**
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The DWARF and CodeView readers use the public names information to create
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the instructions (``LVLineAssembler``). Instead of relying on DWARF section
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names (``.debug_pubnames``, ``.debug_names``) and CodeView public symbol stream
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(``S_PUB32``), the readers should collect the needed information while processing
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the debug information.
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If the object file supports the above section names and stream, use them
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to create the public names.
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### Add support for some extra DWARF locations.
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The following DWARF debug location operands are not supported:
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* `DW_OP_const_type`
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* `DW_OP_entry_value`
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* `DW_OP_implicit_value`
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### Add support for additional binary formats.
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* Extended COFF (`XCOFF`)
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### Add support for ``JSON`` or ``YAML``
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The logical view uses its own and non-standard free form text when
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displaying information on logical elements.
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