mirror of
https://github.com/LadybirdBrowser/ladybird.git
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f6aee2b9e8
Instead of keeping bytecode as a set of disjoint basic blocks on the
malloc heap, bytecode is now a contiguous sequence of bytes(!)
The transformation happens at the end of Bytecode::Generator::generate()
and the only really hairy part is rerouting jump labels.
This required solving a few problems:
- The interpreter execution loop had to change quite a bit, since we
were storing BasicBlock pointers all over the place, and control
transfer was done by redirecting the interpreter's current block.
- Exception handlers & finalizers are now stored per-bytecode-range
in a side table in Executable.
- The interpreter now has a plain program counter instead of a stream
iterator. This actually makes error stack generation a bit nicer
since we just have to deal with a number instead of reaching into
the iterator.
This yields a 25% performance improvement on this microbenchmark:
for (let i = 0; i < 1_000_000; ++i) { }
But basically everything gets faster. :^)
107 lines
3.5 KiB
C++
107 lines
3.5 KiB
C++
/*
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* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <LibJS/Bytecode/Executable.h>
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#include <LibJS/Bytecode/Label.h>
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#include <LibJS/Bytecode/Register.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Heap/Cell.h>
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#include <LibJS/Runtime/FunctionKind.h>
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#include <LibJS/Runtime/VM.h>
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#include <LibJS/Runtime/Value.h>
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namespace JS::Bytecode {
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class InstructionStreamIterator;
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class Interpreter {
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public:
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explicit Interpreter(VM&);
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~Interpreter();
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[[nodiscard]] Realm& realm() { return *m_realm; }
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[[nodiscard]] Object& global_object() { return *m_global_object; }
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[[nodiscard]] DeclarativeEnvironment& global_declarative_environment() { return *m_global_declarative_environment; }
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VM& vm() { return m_vm; }
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VM const& vm() const { return m_vm; }
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ThrowCompletionOr<Value> run(Script&, JS::GCPtr<Environment> lexical_environment_override = nullptr);
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ThrowCompletionOr<Value> run(SourceTextModule&);
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ThrowCompletionOr<Value> run(Bytecode::Executable& executable, Optional<size_t> entry_point = {}, Value initial_accumulator_value = {})
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{
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auto result_and_return_register = run_executable(executable, entry_point, initial_accumulator_value);
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return move(result_and_return_register.value);
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}
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struct ResultAndReturnRegister {
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ThrowCompletionOr<Value> value;
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Value return_register_value;
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};
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ResultAndReturnRegister run_executable(Bytecode::Executable&, Optional<size_t> entry_point, Value initial_accumulator_value = {});
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ALWAYS_INLINE Value& accumulator() { return reg(Register::accumulator()); }
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ALWAYS_INLINE Value& saved_return_value() { return reg(Register::saved_return_value()); }
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Value& reg(Register const& r)
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{
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return m_registers.data()[r.index()];
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}
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Value reg(Register const& r) const
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{
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return m_registers.data()[r.index()];
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}
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[[nodiscard]] Value get(Operand) const;
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void set(Operand, Value);
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void do_return(Value value)
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{
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reg(Register::return_value()) = value;
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reg(Register::exception()) = {};
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}
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void enter_unwind_context();
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void leave_unwind_context();
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void catch_exception(Operand dst);
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void restore_scheduled_jump();
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void leave_finally();
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void enter_object_environment(Object&);
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Executable& current_executable() { return *m_current_executable; }
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Executable const& current_executable() const { return *m_current_executable; }
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Optional<size_t> program_counter() const { return m_program_counter; }
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Vector<Value>& registers() { return vm().running_execution_context().registers; }
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Vector<Value> const& registers() const { return vm().running_execution_context().registers; }
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private:
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void run_bytecode(size_t entry_point);
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enum class HandleExceptionResponse {
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ExitFromExecutable,
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ContinueInThisExecutable,
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};
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[[nodiscard]] HandleExceptionResponse handle_exception(size_t& program_counter, Value exception);
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VM& m_vm;
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Optional<size_t> m_scheduled_jump;
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GCPtr<Executable> m_current_executable { nullptr };
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GCPtr<Realm> m_realm { nullptr };
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GCPtr<Object> m_global_object { nullptr };
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GCPtr<DeclarativeEnvironment> m_global_declarative_environment { nullptr };
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Optional<size_t&> m_program_counter;
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Span<Value> m_registers;
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Span<Value> m_locals;
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};
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extern bool g_dump_bytecode;
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ThrowCompletionOr<NonnullGCPtr<Bytecode::Executable>> compile(VM&, ASTNode const&, ReadonlySpan<FunctionParameter>, JS::FunctionKind kind, DeprecatedFlyString const& name);
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}
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