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LibJS: Devirtualize and pack the bytecode stream :^)

This patch changes the LibJS bytecode to be a stream of instructions
packed one-after-the-other in contiguous memory, instead of a vector
of OwnPtr<Instruction>. This should be a lot more cache-friendly. :^)

Instructions are also devirtualized and instead have a type field
using a new Instruction::Type enum.

To iterate over a bytecode stream, one must now use
Bytecode::InstructionStreamIterator.
This commit is contained in:
Andreas Kling 2021-06-07 15:12:43 +02:00
parent 845f2826aa
commit e7d69c5d3c
11 changed files with 284 additions and 110 deletions

View file

@ -12,24 +12,55 @@
namespace JS::Bytecode {
class InstructionStreamIterator {
public:
explicit InstructionStreamIterator(ReadonlyBytes bytes)
: m_bytes(bytes)
{
}
size_t offset() const { return m_offset; }
bool at_end() const { return m_offset >= m_bytes.size(); }
void jump(size_t offset)
{
VERIFY(offset <= m_bytes.size());
m_offset = offset;
}
Instruction const& operator*() const { return dereference(); }
void operator++();
private:
Instruction const& dereference() const { return *reinterpret_cast<Instruction const*>(m_bytes.data() + offset()); }
ReadonlyBytes m_bytes;
size_t m_offset { 0 };
};
class Block {
public:
static NonnullOwnPtr<Block> create();
~Block();
NonnullOwnPtrVector<Instruction> const& instructions() const { return m_instructions; }
void dump() const;
ReadonlyBytes instruction_stream() const { return ReadonlyBytes { m_buffer, m_buffer_size }; }
size_t register_count() const { return m_register_count; }
void append(Badge<Bytecode::Generator>, NonnullOwnPtr<Instruction>);
void set_register_count(Badge<Bytecode::Generator>, size_t count) { m_register_count = count; }
void* next_slot() { return m_buffer + m_buffer_size; }
void grow(size_t additional_size);
private:
Block();
size_t m_register_count { 0 };
NonnullOwnPtrVector<Instruction> m_instructions;
u8* m_buffer { nullptr };
size_t m_buffer_capacity { 0 };
size_t m_buffer_size { 0 };
u8 const* m_buffer_end { nullptr };
};
}