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LibJS/Bytecode: Don't create empty lexical environments

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This patch stops emitting the BlockDeclarationInstantiation instruction
when there are no locals, and no function declarations in the scope.

We were spending 20% of CPU time on https://ventrella.com/Clusters/ just
creating empty environments for no reason.
This commit is contained in:
Andreas Kling 2024-05-11 13:25:08 +02:00
parent 9e976dfeac
commit b5a070e8ce
Notes: sideshowbarker 2024-07-17 06:39:26 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/b5a070e8ce
Pull-request: https://github.com/SerenityOS/serenity/pull/24284
3 changed files with 26 additions and 8 deletions
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11
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -44,8 +44,7 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> ScopeNode::generate_byt
if (is<BlockStatement>(*this)) {
if (has_lexical_declarations()) {
generator.block_declaration_instantiation(*this);
did_create_lexical_environment = true;
did_create_lexical_environment = generator.emit_block_declaration_instantiation(*this);
}
} else if (is<Program>(*this)) {
// GlobalDeclarationInstantiation is handled by the C++ AO.
@ -2655,9 +2654,9 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> SwitchStatement::genera
Bytecode::BasicBlock* entry_block_for_default { nullptr };
Bytecode::BasicBlock* next_test_block = &generator.make_block();
auto has_lexical_declarations = this->has_lexical_declarations();
if (has_lexical_declarations)
generator.block_declaration_instantiation(*this);
bool did_create_lexical_environment = false;
if (has_lexical_declarations())
did_create_lexical_environment = generator.emit_block_declaration_instantiation(*this);
generator.emit<Bytecode::Op::Jump>(Bytecode::Label { *next_test_block });
@ -2721,7 +2720,7 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> SwitchStatement::genera
generator.switch_to_basic_block(end_block);
if (has_lexical_declarations)
if (did_create_lexical_environment)
generator.end_variable_scope();
return dst;

20
Userland/Libraries/LibJS/Bytecode/Generator.cpp
View file

@ -448,10 +448,28 @@ Label Generator::nearest_continuable_scope() const
return m_continuable_scopes.last().bytecode_target;
}
void Generator::block_declaration_instantiation(ScopeNode const& scope_node)
bool Generator::emit_block_declaration_instantiation(ScopeNode const& scope_node)
{
bool needs_block_declaration_instantiation = false;
MUST(scope_node.for_each_lexically_scoped_declaration([&](Declaration const& declaration) {
if (declaration.is_function_declaration()) {
needs_block_declaration_instantiation = true;
return;
}
MUST(declaration.for_each_bound_identifier([&](auto const& id) {
if (!id.is_local())
needs_block_declaration_instantiation = true;
}));
}));
if (!needs_block_declaration_instantiation)
return false;
// FIXME: Generate the actual bytecode for block declaration instantiation
// and get rid of the BlockDeclarationInstantiation instruction.
start_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
emit<Bytecode::Op::BlockDeclarationInstantiation>(scope_node);
return true;
}
void Generator::begin_variable_scope()

3
Userland/Libraries/LibJS/Bytecode/Generator.h
View file

@ -213,7 +213,8 @@ public:
SurroundingScopeKind kind;
};
void block_declaration_instantiation(ScopeNode const&);
// Returns true if a lexical environment was created.
bool emit_block_declaration_instantiation(ScopeNode const&);
void begin_variable_scope();
void end_variable_scope();