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LibJS: Use a Vector<u8> for BasicBlock instruction storage

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This reduces the minimum size of a basic block from 4 KiB to 0 bytes.
With this change, memory usage at the end of Speedometer is 1.2 GiB,
down from 1.8 GiB.
This commit is contained in:
Andreas Kling 2023-09-28 09:29:42 +02:00
parent 89a86798a2
commit d24e07579f
4 changed files with 20 additions and 67 deletions
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32
Userland/Libraries/LibJS/Bytecode/Generator.h
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@ -34,18 +34,6 @@ public:
Register allocate_register();
void ensure_enough_space(size_t size)
{
// Make sure there's always enough space for a single jump at the end.
if (!m_current_basic_block->can_grow(size + sizeof(Op::Jump))) {
auto& new_block = make_block();
emit<Op::Jump>().set_targets(
Label { new_block },
{});
switch_to_basic_block(new_block);
}
}
class SourceLocationScope {
public:
SourceLocationScope(Generator&, ASTNode const& node);
@ -60,15 +48,12 @@ public:
OpType& emit(Args&&... args)
{
VERIFY(!is_current_block_terminated());
// If the block doesn't have enough space, switch to another block
if constexpr (!OpType::IsTerminator)
ensure_enough_space(sizeof(OpType));
void* slot = next_slot();
size_t slot_offset = m_current_basic_block->size();
grow(sizeof(OpType));
void* slot = m_current_basic_block->data() + slot_offset;
new (slot) OpType(forward<Args>(args)...);
if constexpr (OpType::IsTerminator)
m_current_basic_block->terminate({}, static_cast<Instruction const*>(slot));
m_current_basic_block->terminate({});
auto* op = static_cast<OpType*>(slot);
op->set_source_record({ m_current_ast_node->start_offset(), m_current_ast_node->end_offset() });
return *op;
@ -80,16 +65,12 @@ public:
VERIFY(!is_current_block_terminated());
size_t size_to_allocate = round_up_to_power_of_two(sizeof(OpType) + extra_register_slots * sizeof(Register), alignof(void*));
// If the block doesn't have enough space, switch to another block
if constexpr (!OpType::IsTerminator)
ensure_enough_space(size_to_allocate);
void* slot = next_slot();
size_t slot_offset = m_current_basic_block->size();
grow(size_to_allocate);
void* slot = m_current_basic_block->data() + slot_offset;
new (slot) OpType(forward<Args>(args)...);
if constexpr (OpType::IsTerminator)
m_current_basic_block->terminate({}, static_cast<Instruction const*>(slot));
m_current_basic_block->terminate({});
auto* op = static_cast<OpType*>(slot);
op->set_source_record({ m_current_ast_node->start_offset(), m_current_ast_node->end_offset() });
return *op;
@ -238,7 +219,6 @@ private:
~Generator() = default;
void grow(size_t);
void* next_slot();
struct LabelableScope {
Label bytecode_target;