Files
clang-p2996/lldb/source/Plugins/SymbolFile/DWARF/NameToDIE.cpp
Pavel Labath 7afd052112 [lldb/DWARF] Make manual dwarf index deterministic
Currently, running the test suite with LLVM_ENABLE_EXPENSIVE_CHECKS=On
causes a couple of tests to fail. This happens because they expect a
certain order of variables (all of them happen to use the "target
variable" command, but other lookup functions should suffer from the
same issues), all of which have the same name. Sort algorithms often
preserve the order of equivalent elements (in this case the entries in
the NameToDIE map), but that not guaranteed, and
LLVM_ENABLE_EXPENSIVE_CHECKS stresses that by pre-shuffling all inputs
before sorting.

While this could easily be fixed by relaxing the test expectations,
having a deterministic output seems like a worthwhile goal,
particularly, as this could have bigger consequences than just a
different print order -- in some cases we just pick the first entry that
we find, whatever that is. Therefore this patch makes the sort
deterministic by introducing another sort key -- UniqueCString::Sort
gets a value comparator functor, which can be used to sort elements with
the same name -- in the DWARF case we use DIERef::operator<, which
roughly equals the order in which the entries appear in the debug info,
and matches the current "accidental" order.

Using a extra functor seemed preferable to using stable_sort, as the
latter allocates extra O(n) of temporary memory.

I observed no difference in debug info parsing speed with this patch
applied.

Differential Revision: https://reviews.llvm.org/D118251
2022-01-27 10:05:05 +01:00

140 lines
4.5 KiB
C++

//===-- NameToDIE.cpp -----------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "NameToDIE.h"
#include "DWARFUnit.h"
#include "lldb/Core/DataFileCache.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Utility/ConstString.h"
#include "lldb/Utility/DataEncoder.h"
#include "lldb/Utility/DataExtractor.h"
#include "lldb/Utility/RegularExpression.h"
#include "lldb/Utility/Stream.h"
#include "lldb/Utility/StreamString.h"
using namespace lldb;
using namespace lldb_private;
void NameToDIE::Finalize() {
m_map.Sort(std::less<DIERef>());
m_map.SizeToFit();
}
void NameToDIE::Insert(ConstString name, const DIERef &die_ref) {
m_map.Append(name, die_ref);
}
bool NameToDIE::Find(ConstString name,
llvm::function_ref<bool(DIERef ref)> callback) const {
for (const auto &entry : m_map.equal_range(name))
if (!callback(entry.value))
return false;
return true;
}
bool NameToDIE::Find(const RegularExpression &regex,
llvm::function_ref<bool(DIERef ref)> callback) const {
for (const auto &entry : m_map)
if (regex.Execute(entry.cstring.GetCString())) {
if (!callback(entry.value))
return false;
}
return true;
}
void NameToDIE::FindAllEntriesForUnit(
DWARFUnit &s_unit, llvm::function_ref<bool(DIERef ref)> callback) const {
lldbassert(!s_unit.GetSymbolFileDWARF().GetDwoNum());
const DWARFUnit &ns_unit = s_unit.GetNonSkeletonUnit();
const uint32_t size = m_map.GetSize();
for (uint32_t i = 0; i < size; ++i) {
const DIERef &die_ref = m_map.GetValueAtIndexUnchecked(i);
if (ns_unit.GetSymbolFileDWARF().GetDwoNum() == die_ref.dwo_num() &&
ns_unit.GetDebugSection() == die_ref.section() &&
ns_unit.GetOffset() <= die_ref.die_offset() &&
die_ref.die_offset() < ns_unit.GetNextUnitOffset()) {
if (!callback(die_ref))
return;
}
}
}
void NameToDIE::Dump(Stream *s) {
const uint32_t size = m_map.GetSize();
for (uint32_t i = 0; i < size; ++i) {
s->Format("{0} \"{1}\"\n", m_map.GetValueAtIndexUnchecked(i),
m_map.GetCStringAtIndexUnchecked(i));
}
}
void NameToDIE::ForEach(
std::function<bool(ConstString name, const DIERef &die_ref)> const
&callback) const {
const uint32_t size = m_map.GetSize();
for (uint32_t i = 0; i < size; ++i) {
if (!callback(m_map.GetCStringAtIndexUnchecked(i),
m_map.GetValueAtIndexUnchecked(i)))
break;
}
}
void NameToDIE::Append(const NameToDIE &other) {
const uint32_t size = other.m_map.GetSize();
for (uint32_t i = 0; i < size; ++i) {
m_map.Append(other.m_map.GetCStringAtIndexUnchecked(i),
other.m_map.GetValueAtIndexUnchecked(i));
}
}
constexpr llvm::StringLiteral kIdentifierNameToDIE("N2DI");
bool NameToDIE::Decode(const DataExtractor &data, lldb::offset_t *offset_ptr,
const StringTableReader &strtab) {
m_map.Clear();
llvm::StringRef identifier((const char *)data.GetData(offset_ptr, 4), 4);
if (identifier != kIdentifierNameToDIE)
return false;
const uint32_t count = data.GetU32(offset_ptr);
for (uint32_t i = 0; i < count; ++i) {
llvm::StringRef str(strtab.Get(data.GetU32(offset_ptr)));
// No empty strings allowed in the name to DIE maps.
if (str.empty())
return false;
if (llvm::Optional<DIERef> die_ref = DIERef::Decode(data, offset_ptr))
m_map.Append(ConstString(str), die_ref.getValue());
else
return false;
}
return true;
}
void NameToDIE::Encode(DataEncoder &encoder, ConstStringTable &strtab) const {
encoder.AppendData(kIdentifierNameToDIE);
encoder.AppendU32(m_map.GetSize());
for (const auto &entry : m_map) {
// Make sure there are no empty strings.
assert((bool)entry.cstring);
encoder.AppendU32(strtab.Add(entry.cstring));
entry.value.Encode(encoder);
}
}
bool NameToDIE::operator==(const NameToDIE &rhs) const {
const size_t size = m_map.GetSize();
if (size != rhs.m_map.GetSize())
return false;
for (size_t i = 0; i < size; ++i) {
if (m_map.GetCStringAtIndex(i) != rhs.m_map.GetCStringAtIndex(i))
return false;
if (m_map.GetValueRefAtIndexUnchecked(i) !=
rhs.m_map.GetValueRefAtIndexUnchecked(i))
return false;
}
return true;
}