RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-25 15:27:35 +00:00
Code Issues Activity Actions

LibDebug: Avoid short lived allocations in DIE::for_each_child

Browse source 
This algorithm is both iterative and recursive, so allocating on every
recursion, or when iterating each child is extremely costly.

Instead allow the on stack DIE to be re-initialized so it can be reused.
This commit is contained in:
Brian Gianforcaro 2021-09-17 02:12:29 -07:00 • committed by Andreas Kling
parent 19c492e976
commit 952441943f
2 changed files with 17 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

28
Userland/Libraries/LibDebug/Dwarf/DIE.cpp
View file

@ -14,8 +14,14 @@ namespace Debug::Dwarf {
DIE::DIE(CompilationUnit const& unit, u32 offset, Optional<u32> parent_offset) DIE::DIE(CompilationUnit const& unit, u32 offset, Optional<u32> parent_offset)
: m_compilation_unit(unit) : m_compilation_unit(unit)
, m_offset(offset)
{ {
rehydrate_from(offset, parent_offset);
}
void DIE::rehydrate_from(u32 offset, Optional<u32> parent_offset)
{
m_offset = offset;
InputMemoryStream stream(m_compilation_unit.dwarf_info().debug_info_data()); InputMemoryStream stream(m_compilation_unit.dwarf_info().debug_info_data());
stream.discard_or_error(m_offset); stream.discard_or_error(m_offset);
stream.read_LEB128_unsigned(m_abbreviation_code); stream.read_LEB128_unsigned(m_abbreviation_code);
@ -62,30 +68,28 @@ void DIE::for_each_child(Function<void(DIE const& child)> callback) const
if (!m_has_children) if (!m_has_children)
return; return;
NonnullOwnPtr<DIE> current_child = make<DIE>(m_compilation_unit, m_offset + m_size, m_offset); auto current_child = DIE(m_compilation_unit, m_offset + m_size, m_offset);
while (true) { while (true) {
callback(*current_child); callback(current_child);
if (current_child->is_null()) if (current_child.is_null())
break; break;
if (!current_child->has_children()) { if (!current_child.has_children()) {
current_child = make<DIE>(m_compilation_unit, current_child->offset() + current_child->size(), m_offset); current_child.rehydrate_from(current_child.offset() + current_child.size(), m_offset);
continue; continue;
} }
auto sibling = current_child->get_attribute(Attribute::Sibling); auto sibling = current_child.get_attribute(Attribute::Sibling);
u32 sibling_offset = 0; u32 sibling_offset = 0;
if (sibling.has_value()) { if (sibling.has_value()) {
sibling_offset = sibling.value().data.as_unsigned; sibling_offset = sibling.value().data.as_unsigned;
} } else {
if (!sibling.has_value()) {
// NOTE: According to the spec, the compiler doesn't have to supply the sibling information. // NOTE: According to the spec, the compiler doesn't have to supply the sibling information.
// When it doesn't, we have to recursively iterate the current child's children to find where they end // When it doesn't, we have to recursively iterate the current child's children to find where they end
current_child->for_each_child([&](DIE const& sub_child) { current_child.for_each_child([&](DIE const& sub_child) {
sibling_offset = sub_child.offset() + sub_child.size(); sibling_offset = sub_child.offset() + sub_child.size();
}); });
} }
current_child = make<DIE>(m_compilation_unit, sibling_offset, m_offset); current_child.rehydrate_from(sibling_offset, m_offset);
} }
} }

1
Userland/Libraries/LibDebug/Dwarf/DIE.h
View file

@ -36,6 +36,7 @@ public:
Optional<u32> parent_offset() const { return m_parent_offset; } Optional<u32> parent_offset() const { return m_parent_offset; }
private: private:
void rehydrate_from(u32 offset, Optional<u32> parent_offset);
CompilationUnit const& m_compilation_unit; CompilationUnit const& m_compilation_unit;
u32 m_offset { 0 }; u32 m_offset { 0 };
u32 m_data_offset { 0 }; u32 m_data_offset { 0 };