[all-commits] [llvm/llvm-project] 61a467: Improve type lookup using .debug_names parent chai...

[jeffreytan81 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 61a46780d10c8f4e12c9b5496f5ca3f2cc7fba66
      https://github.com/llvm/llvm-project/commit/61a46780d10c8f4e12c9b5496f5ca3f2cc7fba66
  Author: jeffreytan81 <jeffreytan at meta.com>
  Date:   2024-10-09 (Wed, 09 Oct 2024)

  Changed paths:
    M lldb/source/Plugins/SymbolFile/DWARF/DWARFIndex.cpp
    M lldb/source/Plugins/SymbolFile/DWARF/DWARFIndex.h
    M lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp
    M lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.h
    M lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

  Log Message:
  -----------
  Improve type lookup using .debug_names parent chain (#108907)

## Summary
This PR improves `SymbolFileDWARF::FindTypes()` by utilizing the newly
added parent chain `DW_IDX_parent` in `.debug_names`. The proposal was
originally discussed in [this
RFC](https://discourse.llvm.org/t/rfc-improve-dwarf-5-debug-names-type-lookup-parsing-speed/74151).

## Implementation
To leverage the parent chain for `SymbolFileDWARF::FindTypes()`, this PR
adds a new API: `GetTypesWithQuery` in `DWARFIndex` base class. The API
performs the same function as `GetTypes` with additional filtering using
`TypeQuery`. Since this only introduces filtering, the callback
mechanisms at all call sites remain unchanged. A default implementation
is given in `DWARFIndex` class which parses debug info and performs the
matching. In the `DebugNameDWARFIndex` override, the parent_contexts in
the `TypeQuery` is cross checked with parent chain in `.debug_names` for
for much faster filtering before fallback to base implementation for
final filtering.

Unlike the `GetFullyQualifiedType` API, which fully consumes the
`DW_IDX_parent` parent chain for exact matching, these new APIs perform
partial subset matching for type/namespace queries. This is necessary to
support queries involving anonymous or inline namespaces. For instance,
a user might request `NS1::NS2::NS3::Foo`, while the index table's
parent chain might contain `NS1::inline_NS2::NS3::Foo`, which would fail
exact matching.

## Performance Results
In one of our internal target using `.debug_names` + split dwarf.
Expanding a "this" pointer in locals view in VSCode:
94s => 48s. (Not sure why I got 94s this time instead of 70s last week).

---------

Co-authored-by: jeffreytan81 <jeffreytan at fb.com>



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications