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LibJS: Start fleshing out a bytecode for the JavaScript engine :^)

This patch begins the work of implementing JavaScript execution in a
bytecode VM instead of an AST tree-walk interpreter.

It's probably quite naive, but we have to start somewhere.

The basic idea is that you call Bytecode::Generator::generate() on an
AST node and it hands you back a Bytecode::Block filled with
instructions that can then be interpreted by a Bytecode::Interpreter.

This first version only implements two instructions: Load and Add. :^)

Each bytecode block has infinity registers, and the interpreter resizes
its register file to fit the block being executed.

Two new `js` options are added in this patch as well:

`-d` will dump the generated bytecode
`-b` will execute the generated bytecode

Note that unless `-d` and/or `-b` are specified, none of the bytecode
related stuff in LibJS runs at all. This is implemented in parallel
with the existing AST interpreter. :^)
This commit is contained in:
Andreas Kling 2021-06-03 10:46:30 +02:00
parent f9395efaac
commit 69dddd4ef5
16 changed files with 487 additions and 24 deletions

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/String.h>
#include <LibJS/Bytecode/Block.h>
#include <LibJS/Bytecode/Instruction.h>
namespace JS::Bytecode {
NonnullOwnPtr<Block> Block::create()
{
return adopt_own(*new Block);
}
Block::Block()
{
}
Block::~Block()
{
}
void Block::append(Badge<Bytecode::Generator>, NonnullOwnPtr<Instruction> instruction)
{
m_instructions.append(move(instruction));
}
void Block::dump() const
{
for (size_t i = 0; i < m_instructions.size(); ++i) {
warnln("[{:3}] {}", i, m_instructions[i].to_string());
}
}
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Badge.h>
#include <AK/NonnullOwnPtrVector.h>
#include <LibJS/Forward.h>
namespace JS::Bytecode {
class Block {
public:
static NonnullOwnPtr<Block> create();
~Block();
NonnullOwnPtrVector<Instruction> const& instructions() const { return m_instructions; }
void dump() const;
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; }
private:
Block();
size_t m_register_count { 0 };
NonnullOwnPtrVector<Instruction> m_instructions;
};
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/OwnPtr.h>
#include <LibJS/AST.h>
#include <LibJS/Bytecode/Block.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Instruction.h>
#include <LibJS/Bytecode/Register.h>
#include <LibJS/Forward.h>
namespace JS::Bytecode {
Generator::Generator()
{
m_block = Block::create();
}
Generator::~Generator()
{
}
OwnPtr<Block> Generator::generate(ASTNode const& node)
{
Generator generator;
[[maybe_unused]] auto dummy = node.generate_bytecode(generator);
generator.m_block->set_register_count({}, generator.m_next_register);
return move(generator.m_block);
}
void Generator::append(NonnullOwnPtr<Instruction> instruction)
{
m_block->append({}, move(instruction));
}
Register Generator::allocate_register()
{
VERIFY(m_next_register != NumericLimits<u32>::max());
return Register { m_next_register++ };
}
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/OwnPtr.h>
#include <LibJS/Forward.h>
namespace JS::Bytecode {
class Generator {
public:
static OwnPtr<Block> generate(ASTNode const&);
Register allocate_register();
template<typename OpType, typename... Args>
void emit(Args&&... args)
{
auto instruction = make<OpType>(forward<Args>(args)...);
append(move(instruction));
}
private:
Generator();
~Generator();
void append(NonnullOwnPtr<Instruction>);
OwnPtr<Block> m_block;
u32 m_next_register { 1 };
};
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Bytecode/Instruction.h>
namespace JS::Bytecode {
Instruction::~Instruction()
{
}
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Forward.h>
#include <LibJS/Forward.h>
namespace JS::Bytecode {
class Instruction {
public:
virtual ~Instruction();
virtual String to_string() const = 0;
virtual void execute(Bytecode::Interpreter&) const = 0;
};
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Bytecode/Block.h>
#include <LibJS/Bytecode/Instruction.h>
#include <LibJS/Bytecode/Interpreter.h>
namespace JS::Bytecode {
Interpreter::Interpreter(GlobalObject& global_object)
: m_global_object(global_object)
{
}
Interpreter::~Interpreter()
{
}
void Interpreter::run(Bytecode::Block const& block)
{
dbgln("Bytecode::Interpreter will run block {:p}", &block);
m_registers.resize(block.register_count());
for (auto& instruction : block.instructions())
instruction.execute(*this);
dbgln("Bytecode::Interpreter did run block {:p}", &block);
for (size_t i = 0; i < m_registers.size(); ++i) {
String value_string;
if (m_registers[i].is_empty())
value_string = "(empty)";
else
value_string = m_registers[i].to_string_without_side_effects();
dbgln("[{:3}] {}", i, value_string);
}
}
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibJS/Bytecode/Register.h>
#include <LibJS/Forward.h>
#include <LibJS/Heap/Cell.h>
#include <LibJS/Runtime/Value.h>
namespace JS::Bytecode {
class Interpreter {
public:
explicit Interpreter(GlobalObject&);
~Interpreter();
GlobalObject& global_object() { return m_global_object; }
void run(Bytecode::Block const&);
Value& reg(Register const& r) { return m_registers[r.index()]; }
private:
GlobalObject& m_global_object;
Vector<Value> m_registers;
};
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Bytecode/Interpreter.h>
#include <LibJS/Bytecode/Op.h>
#include <LibJS/Runtime/Value.h>
namespace JS::Bytecode::Op {
void Load::execute(Bytecode::Interpreter& interpreter) const
{
interpreter.reg(m_dst) = m_value;
}
void Add::execute(Bytecode::Interpreter& interpreter) const
{
interpreter.reg(m_dst) = add(interpreter.global_object(), interpreter.reg(m_src1), interpreter.reg(m_src2));
}
String Load::to_string() const
{
return String::formatted("Load dst:r{}, value:{}", m_dst.index(), m_value.to_string_without_side_effects());
}
String Add::to_string() const
{
return String::formatted("Add dst:r{}, src1:r{}, src2:r{}", m_dst.index(), m_src1.index(), m_src2.index());
}
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibJS/Bytecode/Instruction.h>
#include <LibJS/Bytecode/Register.h>
#include <LibJS/Heap/Cell.h>
#include <LibJS/Runtime/Value.h>
namespace JS::Bytecode::Op {
class Load final : public Instruction {
public:
Load(Register dst, Value value)
: m_dst(dst)
, m_value(value)
{
}
virtual ~Load() override { }
virtual void execute(Bytecode::Interpreter&) const override;
virtual String to_string() const override;
private:
Register m_dst;
Value m_value;
};
class Add final : public Instruction {
public:
Add(Register dst, Register src1, Register src2)
: m_dst(dst)
, m_src1(src1)
, m_src2(src2)
{
}
virtual ~Add() override { }
virtual void execute(Bytecode::Interpreter&) const override;
virtual String to_string() const override;
private:
Register m_dst;
Register m_src1;
Register m_src2;
};
}

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Types.h>
namespace JS::Bytecode {
class Register {
public:
explicit Register(u32 index)
: m_index(index)
{
}
u32 index() const { return m_index; }
private:
u32 m_index { 0 };
};
}