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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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20
Userland/Libraries/LibJS/Bytecode/Generator.cpp
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@@ -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()