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

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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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50
Userland/Libraries/LibJS/AST.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
@ -13,6 +13,9 @@
#include <AK/TemporaryChange.h>
#include <LibCrypto/BigInt/SignedBigInteger.h>
#include <LibJS/AST.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Op.h>
#include <LibJS/Bytecode/Register.h>
#include <LibJS/Interpreter.h>
#include <LibJS/Runtime/Accessor.h>
#include <LibJS/Runtime/Array.h>
@ -2234,4 +2237,49 @@ void ScopeNode::add_functions(NonnullRefPtrVector<FunctionDeclaration> functions
m_functions.append(move(functions));
}
Optional<Bytecode::Register> ASTNode::generate_bytecode(Bytecode::Generator&) const
{
dbgln("Missing generate_bytecode()");
TODO();
}
Optional<Bytecode::Register> ScopeNode::generate_bytecode(Bytecode::Generator& generator) const
{
for (auto& child : children()) {
[[maybe_unused]] auto reg = child.generate_bytecode(generator);
}
return {};
}
Optional<Bytecode::Register> ExpressionStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return m_expression->generate_bytecode(generator);
}
Optional<Bytecode::Register> BinaryExpression::generate_bytecode(Bytecode::Generator& generator) const
{
auto lhs_reg = m_lhs->generate_bytecode(generator);
auto rhs_reg = m_rhs->generate_bytecode(generator);
VERIFY(lhs_reg.has_value());
VERIFY(rhs_reg.has_value());
switch (m_op) {
case BinaryOp::Addition: {
auto dst_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Add>(dst_reg, *lhs_reg, *rhs_reg);
return dst_reg;
}
default:
TODO();
}
}
Optional<Bytecode::Register> NumericLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
auto dst = generator.allocate_register();
generator.emit<Bytecode::Op::Load>(dst, m_value);
return dst;
}
}