Method rewriteLoop

libyul/optimiser/LoopInvariantCodeMotion.cpp:83–121

}

std::optional<std::vector<Statement>> LoopInvariantCodeMotion::rewriteLoop(ForLoop& _for)
{
	assertThrow(_for.pre.statements.empty(), OptimizerException, "");

	auto forLoopSideEffects =
		SideEffectsCollector{m_dialect, _for, &m_functionSideEffects}.sideEffects();

	std::vector<Statement> replacement;
	for (Block* block: {&_for.post, &_for.body})
	{
		std::set<YulName> varsDefinedInScope;
		util::iterateReplacing(
			block->statements,
			[&](Statement& _s) -> std::optional<std::vector<Statement>>
			{
				if (std::holds_alternative<VariableDeclaration>(_s))
				{
					VariableDeclaration const& varDecl = std::get<VariableDeclaration>(_s);
					if (canBePromoted(varDecl, varsDefinedInScope, forLoopSideEffects))
					{
						replacement.emplace_back(std::move(_s));
						// Do not add the variables declared here to varsDefinedInScope because we are moving them.
						return std::vector<Statement>{};
					}
					for (auto const& var: varDecl.variables)
						varsDefinedInScope.insert(var.name);
				}
				return {};
			}
		);
	}
	if (replacement.empty())
		return {};
	else
	{
		replacement.emplace_back(std::move(_for));
		return { std::move(replacement) };
	}
}