Method fillInJunk

libyul/backends/evm/StackLayoutGenerator.cpp:739–875

}

void StackLayoutGenerator::fillInJunk(CFG::BasicBlock const& _block, CFG::FunctionInfo const* _functionInfo)
{
	/// Recursively adds junk to the subgraph starting on @a _entry.
	/// Since it is only called on cut-vertices, the full subgraph retains proper stack balance.
	auto addJunkRecursive = [&](CFG::BasicBlock const* _entry, size_t _numJunk) {
		util::BreadthFirstSearch<CFG::BasicBlock const*> breadthFirstSearch{{_entry}};
		breadthFirstSearch.run([&](CFG::BasicBlock const* _block, auto _addChild) {
			auto& blockInfo = m_layout.blockInfos.at(_block);
			blockInfo.entryLayout = Stack{_numJunk, JunkSlot{}} + std::move(blockInfo.entryLayout);
			for (auto const& operation: _block->operations)
			{
				auto& operationEntryLayout = m_layout.operationEntryLayout.at(&operation);
				operationEntryLayout = Stack{_numJunk, JunkSlot{}} + std::move(operationEntryLayout);
			}
			blockInfo.exitLayout = Stack{_numJunk, JunkSlot{}} + std::move(blockInfo.exitLayout);

			std::visit(util::GenericVisitor{
				[&](CFG::BasicBlock::MainExit const&) {},
				[&](CFG::BasicBlock::Jump const& _jump)
				{
					_addChild(_jump.target);
				},
				[&](CFG::BasicBlock::ConditionalJump const& _conditionalJump)
				{
					_addChild(_conditionalJump.zero);
					_addChild(_conditionalJump.nonZero);
				},
				[&](CFG::BasicBlock::FunctionReturn const&) { yulAssert(!simulateFunctionsWithJumps()); },
				[&](CFG::BasicBlock::Terminated const&) {},
			}, _block->exit);
		});
	};
	/// @returns the number of operations required to transform @a _source to @a _target.
	auto evaluateTransform = [&](Stack _source, Stack const& _target) -> size_t {
		size_t opGas = 0;
		auto swap = [&](unsigned _swapDepth)
		{
			if (_swapDepth > reachableStackDepth())
				opGas += 1000;
			else
				opGas += evmasm::GasMeter::swapGas(_swapDepth, m_evmDialect.evmVersion());
		};
		auto dupOrPush = [&](StackSlot const& _slot)
		{
			if (canBeFreelyGenerated(_slot))
				opGas += evmasm::GasMeter::runGas(evmasm::pushInstruction(32), m_evmDialect.evmVersion());
			else
			{
				if (auto depth = util::findOffset(_source | ranges::views::reverse, _slot))
				{
					if (*depth < reachableStackDepth())
						opGas += evmasm::GasMeter::dupGas(*depth + 1, m_evmDialect.evmVersion());
					else
						opGas += 1000;
				}
				else
				{
					// This has to be a previously unassigned return variable.