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https://github.com/fergalmoran/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. :^)
48 lines
1004 B
C++
48 lines
1004 B
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 <AK/Format.h>
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#include <LibJS/Bytecode/BasicBlock.h>
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namespace JS::Bytecode {
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class Label {
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public:
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explicit Label(BasicBlock const& block)
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: m_block(&block)
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{
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}
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// Used while compiling.
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BasicBlock const& block() const { return *m_block; }
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// Used after compiling.
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size_t address() const { return m_address; }
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void set_address(size_t address) { m_address = address; }
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private:
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union {
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// Relevant while compiling.
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BasicBlock const* m_block { nullptr };
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// Relevant after compiling.
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size_t m_address;
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};
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};
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}
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template<>
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struct AK::Formatter<JS::Bytecode::Label> : AK::Formatter<FormatString> {
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ErrorOr<void> format(FormatBuilder& builder, JS::Bytecode::Label const& label)
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{
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return AK::Formatter<FormatString>::format(builder, "@{:x}"sv, label.address());
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}
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};
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