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
3.1 KiB
C++
107 lines
3.1 KiB
C++
/*
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* Copyright (c) 2021-2024, 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/DeprecatedFlyString.h>
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#include <AK/HashMap.h>
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#include <AK/NonnullOwnPtr.h>
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#include <AK/OwnPtr.h>
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#include <AK/WeakPtr.h>
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#include <LibJS/Bytecode/IdentifierTable.h>
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#include <LibJS/Bytecode/Label.h>
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#include <LibJS/Bytecode/StringTable.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Heap/Cell.h>
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#include <LibJS/Heap/CellAllocator.h>
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#include <LibJS/Runtime/EnvironmentCoordinate.h>
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#include <LibJS/SourceRange.h>
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namespace JS::Bytecode {
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struct PropertyLookupCache {
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WeakPtr<Shape> shape;
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Optional<u32> property_offset;
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WeakPtr<Object> prototype;
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WeakPtr<PrototypeChainValidity> prototype_chain_validity;
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};
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struct GlobalVariableCache : public PropertyLookupCache {
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u64 environment_serial_number { 0 };
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};
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using EnvironmentVariableCache = Optional<EnvironmentCoordinate>;
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struct SourceRecord {
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u32 source_start_offset {};
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u32 source_end_offset {};
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};
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class Executable final : public Cell {
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JS_CELL(Executable, Cell);
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JS_DECLARE_ALLOCATOR(Executable);
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public:
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Executable(
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Vector<u8> bytecode,
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NonnullOwnPtr<IdentifierTable>,
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NonnullOwnPtr<StringTable>,
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NonnullOwnPtr<RegexTable>,
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Vector<Value> constants,
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NonnullRefPtr<SourceCode const>,
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size_t number_of_property_lookup_caches,
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size_t number_of_global_variable_caches,
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size_t number_of_environment_variable_caches,
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size_t number_of_registers,
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bool is_strict_mode);
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virtual ~Executable() override;
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DeprecatedFlyString name;
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Vector<u8> bytecode;
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Vector<PropertyLookupCache> property_lookup_caches;
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Vector<GlobalVariableCache> global_variable_caches;
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Vector<EnvironmentVariableCache> environment_variable_caches;
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NonnullOwnPtr<StringTable> string_table;
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NonnullOwnPtr<IdentifierTable> identifier_table;
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NonnullOwnPtr<RegexTable> regex_table;
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Vector<Value> constants;
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NonnullRefPtr<SourceCode const> source_code;
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size_t number_of_registers { 0 };
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bool is_strict_mode { false };
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struct ExceptionHandlers {
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size_t start_offset;
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size_t end_offset;
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Optional<size_t> handler_offset;
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Optional<size_t> finalizer_offset;
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};
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Vector<ExceptionHandlers> exception_handlers;
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Vector<size_t> basic_block_start_offsets;
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ByteString const& get_string(StringTableIndex index) const { return string_table->get(index); }
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DeprecatedFlyString const& get_identifier(IdentifierTableIndex index) const { return identifier_table->get(index); }
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Optional<DeprecatedFlyString const&> get_identifier(Optional<IdentifierTableIndex> const& index) const
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{
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if (!index.has_value())
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return {};
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return get_identifier(*index);
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}
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[[nodiscard]] Optional<ExceptionHandlers const&> exception_handlers_for_offset(size_t offset) const;
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[[nodiscard]] UnrealizedSourceRange source_range_at(size_t offset) const;
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void dump() const;
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private:
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virtual void visit_edges(Visitor&) override;
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};
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}
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