Files
clang-p2996/lldb/source/Plugins/SymbolFile/DWARF/DWARFIndex.h
jeffreytan81 61a46780d1 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@fb.com>
2024-10-09 16:29:39 -07:00

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5.3 KiB
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//===-- DWARFIndex.h -------------------------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
#ifndef LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DWARFINDEX_H
#define LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DWARFINDEX_H
#include "Plugins/SymbolFile/DWARF/DIERef.h"
#include "Plugins/SymbolFile/DWARF/DWARFDIE.h"
#include "Plugins/SymbolFile/DWARF/DWARFFormValue.h"
#include "llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h"
#include "lldb/Core/Module.h"
#include "lldb/Target/Statistics.h"
namespace lldb_private::plugin {
namespace dwarf {
class DWARFDeclContext;
class DWARFDIE;
class DWARFIndex {
public:
DWARFIndex(Module &module) : m_module(module) {}
virtual ~DWARFIndex();
virtual void Preload() = 0;
/// Finds global variables with the given base name. Any additional filtering
/// (e.g., to only retrieve variables from a given context) should be done by
/// the consumer.
virtual void
GetGlobalVariables(ConstString basename,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void
GetGlobalVariables(const RegularExpression &regex,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
/// \a cu must be the skeleton unit if possible, not GetNonSkeletonUnit().
virtual void
GetGlobalVariables(DWARFUnit &cu,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void
GetObjCMethods(ConstString class_name,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void
GetCompleteObjCClass(ConstString class_name, bool must_be_implementation,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void GetTypes(ConstString name,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void GetTypes(const DWARFDeclContext &context,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
/// Finds all DIEs whose fully qualified name matches `context`. A base
/// implementation is provided, and it uses the entire CU to check the DIE
/// parent hierarchy. Specializations should override this if they are able
/// to provide a faster implementation.
virtual void
GetFullyQualifiedType(const DWARFDeclContext &context,
llvm::function_ref<bool(DWARFDIE die)> callback);
virtual void
GetNamespaces(ConstString name,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
/// Get type DIEs meeting requires of \a query.
/// in its decl parent chain as subset. A base implementation is provided,
/// Specializations should override this if they are able to provide a faster
/// implementation.
virtual void
GetTypesWithQuery(TypeQuery &query,
llvm::function_ref<bool(DWARFDIE die)> callback);
virtual void
GetFunctions(const Module::LookupInfo &lookup_info, SymbolFileDWARF &dwarf,
const CompilerDeclContext &parent_decl_ctx,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void
GetFunctions(const RegularExpression &regex,
llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
virtual void Dump(Stream &s) = 0;
StatsDuration::Duration GetIndexTime() { return m_index_time; }
protected:
Module &m_module;
StatsDuration m_index_time;
/// Helper function implementing common logic for processing function dies. If
/// the function given by "die" matches search criteria given by
/// "parent_decl_ctx" and "name_type_mask", it calls the callback with the
/// given die.
bool ProcessFunctionDIE(const Module::LookupInfo &lookup_info, DWARFDIE die,
const CompilerDeclContext &parent_decl_ctx,
llvm::function_ref<bool(DWARFDIE die)> callback);
class DIERefCallbackImpl {
public:
DIERefCallbackImpl(const DWARFIndex &index,
llvm::function_ref<bool(DWARFDIE die)> callback,
llvm::StringRef name);
bool operator()(DIERef ref) const;
bool operator()(const llvm::AppleAcceleratorTable::Entry &entry) const;
private:
const DWARFIndex &m_index;
SymbolFileDWARF &m_dwarf;
const llvm::function_ref<bool(DWARFDIE die)> m_callback;
const llvm::StringRef m_name;
};
DIERefCallbackImpl
DIERefCallback(llvm::function_ref<bool(DWARFDIE die)> callback,
llvm::StringRef name = {}) const {
return DIERefCallbackImpl(*this, callback, name);
}
void ReportInvalidDIERef(DIERef ref, llvm::StringRef name) const;
/// Implementation of `GetFullyQualifiedType` to check a single entry,
/// shareable with derived classes.
bool
GetFullyQualifiedTypeImpl(const DWARFDeclContext &context, DWARFDIE die,
llvm::function_ref<bool(DWARFDIE die)> callback);
/// Check if the type \a die can meet the requirements of \a query.
bool
ProcessTypeDIEMatchQuery(TypeQuery &query, DWARFDIE die,
llvm::function_ref<bool(DWARFDIE die)> callback);
};
} // namespace dwarf
} // namespace lldb_private::plugin
#endif // LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DWARFINDEX_H