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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
3 changed files with 26 additions and 8 deletions
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11
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
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@@ -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;