xref: /freebsd/contrib/llvm-project/llvm/tools/llvm-debuginfo-analyzer/README.txt (revision 06c3fb27)

//===- llvm/tools/llvm-debuginfo-analyzer/README.txt ----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains notes collected during the development, review and test.
// It describes limitations, know issues and future work.
//
//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//
// Remove the use of macros in 'LVReader.h' that describe the bumpallocators.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D137933#inline-1389904

Use a standard (or LLVM) map with typeinfo (would need a specialization
to expose equality and hasher) for the allocators and the creation
functions could be a function template.

//===----------------------------------------------------------------------===//
// Use a lit test instead of a unit test for the logical readers.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1324376

As the DebugInfoLogicalView library is sufficiently exposed via the
llvm-debuginfo-analyzer tool, follow the LLVM general approach and
use LIT tests to validate the logical readers.

Convert the unitests:
  llvm-project/llvm/unittests/DebugInfo/LogicalView/CodeViewReaderTest.cpp
  llvm-project/llvm/unittests/DebugInfo/LogicalView/ELFReaderTest.cpp

into LIT tests:
  llvm-project/llvm/test/DebugInfo/LogicalView/CodeViewReader.test
  llvm-project/llvm/test/DebugInfo/LogicalView/ELFReader.test

//===----------------------------------------------------------------------===//
// Eliminate calls to 'getInputFileDirectory()' in the unit tests.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1324359

Rewrite the unittests 'LFReaderTest' and 'CodeViewReaderTest'to eliminate
the call:

  getInputFileDirectory()

as use of that call is discouraged.

See: Use a lit test instead of a unit test for the logical readers.

//===----------------------------------------------------------------------===//
// Fix mismatch between %d/%x format strings and uint64_t type.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D137400
https://github.com/llvm/llvm-project/issues/58758

Incorrect printing of uint64_t on 32-bit platforms.
Add the PRIx64 specifier to the printing code (format()).

//===----------------------------------------------------------------------===//
// Remove 'LVScope::Children' container.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D137933#inline-1373902

Use a chaining iterator over the other containers rather than keep a
separate container 'Children' that mirrors their contents.

//===----------------------------------------------------------------------===//
// Use TableGen for command line options.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125777#inline-1291801

The current trend is to use TableGen for command-line options in tools.
Change command line options to use tablegen as many other LLVM tools.

//===----------------------------------------------------------------------===//
// LVDoubleMap to return optional<ValueType> instead of null pointer.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1294164

The more idiomatic LLVM way to handle this would be to have 'find '
return Optional<ValueType>.

//===----------------------------------------------------------------------===//
// Pass references instead of pointers (Comparison functions).
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125782#inline-1293920

In the comparison functions, pass references instead of pointers (when
pointers cannot be null).

//===----------------------------------------------------------------------===//
// Use StringMap where possible.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1294211

LLVM has a StringMap class that is advertised as more efficient than
std::map<std::string, ValueType>. Mainly it does fewer allocations
because the key is not a std::string.

Replace the use of std::map<std::string, ValueType> with String Map.
One specific case is the LVSymbolNames definitions.

//===----------------------------------------------------------------------===//
// Calculate unique offset for CodeView elements.
//===----------------------------------------------------------------------===//
In order to have the same logical functionality as the ELF Reader, such
as:

- find scopes contribution to debug info
- sort by its physical location

The logical elements must have an unique offset (similar like the DWARF
DIE offset).

//===----------------------------------------------------------------------===//
// Move 'initializeFileAndStringTables' to the COFF Library.
//===----------------------------------------------------------------------===//
There is some code in the CodeView reader that was extracted/adapted
from 'tools/llvm-readobj/COFFDumper.cpp' that can be moved to the COFF
library.

We had a similar case with code shared with llvm-pdbutil that was moved
to the PDB library: https://reviews.llvm.org/D122226

//===----------------------------------------------------------------------===//
// Move 'getSymbolKindName'/'formatRegisterId' to the CodeView Library.
//===----------------------------------------------------------------------===//
There is some code in the CodeView reader that was extracted/adapted
from 'lib/DebugInfo/CodeView/SymbolDumper.cpp' that can be used.

//===----------------------------------------------------------------------===//
// Use of std::unordered_set instead of std::set.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125784#inline-1221421

Replace the std::set usage for DeducedScopes, UnresolvedScopes and
IdentifiedNamespaces with std::unordered_set and get the benefit
of the O(1) while inserting/searching, as the order is not important.

//===----------------------------------------------------------------------===//
// Optimize 'LVNamespaceDeduction::find' funtion.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125784#inline-1296195

Optimize the 'find' method to use the proposed code:

  LVStringRefs::iterator Iter = std::find_if(Components.begin(), Components.end(),
    [](StringRef Name) {
        return IdentifiedNamespaces.find(Name) == IdentifiedNamespaces.end();
    });
  LVStringRefs::size_type FirstNonNamespace = std::distance(Components.begin(), Iter);

//===----------------------------------------------------------------------===//
// Move all the printing support to a common module.
//===----------------------------------------------------------------------===//
Factor out printing functionality from the logical elements into a
common module.

//===----------------------------------------------------------------------===//
// Refactor 'LVBinaryReader::processLines'.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1246155
https://reviews.llvm.org/D137156

During the traversal of the debug information sections, we created the
logical lines representing the disassembled instructions from the text
section and the logical lines representing the line records from the
debug line section. Using the ranges associated with the logical scopes,
we will allocate those logical lines to their logical scopes.

Consider the case when any of those lines become orphans, causing
incorrect scope parent for disassembly or line records.

//===----------------------------------------------------------------------===//
// Add support for '-ffunction-sections'.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1295012

Only linked executables are handled. It does not support relocatable
files compiled with -ffunction-sections.

//===----------------------------------------------------------------------===//
// Add support for DWARF v5 .debug_names section.
// Add support for CodeView public symbols stream.
//===----------------------------------------------------------------------===//
https://reviews.llvm.org/D125783#inline-1294142

The ELF and CodeView readers use the public names information to create
the instructions (LVLineAssembler). Instead of relying on DWARF section
names (.debug_pubnames, .debug_names) and CodeView public symbol stream
(S_PUB32), the readers collects the needed information while processing
the debug information.

If the object file supports the above section names and stream, use them
to create the public names.

//===----------------------------------------------------------------------===//
// Add support for some extra DWARF locations.
//===----------------------------------------------------------------------===//
The following DWARF debug location operands are not supported:

- DW_OP_const_type
- DW_OP_entry_value
- DW_OP_implicit_value

//===----------------------------------------------------------------------===//
// Add support for additional binary formats.
//===----------------------------------------------------------------------===//
- WebAssembly (Wasm).
  https://github.com/llvm/llvm-project/issues/57040#issuecomment-1211336680

- Extended COFF (XCOFF)

//===----------------------------------------------------------------------===//
// Add support for JSON or YAML.
//===----------------------------------------------------------------------===//
The logical view uses its own and non-standard free form text when
displaying information on logical elements.

//===----------------------------------------------------------------------===//