Optimized EVM Code Transform.

libyul/AST.h

@@ -83,18 +83,16 @@ struct Continue { std::shared_ptr<DebugData const> debugData; };
 /// Leave statement (valid within function)
 struct Leave { std::shared_ptr<DebugData const> debugData; };
 
-struct LocationExtractor
-{
-	template <class T> langutil::SourceLocation operator()(T const& _node) const
-	{
-		return _node.debugData ? _node.debugData->location : langutil::SourceLocation{};
-	}
-};
-
 /// Extracts the source location from a Yul node.
 template <class T> inline langutil::SourceLocation locationOf(T const& _node)
 {
-	return std::visit(LocationExtractor(), _node);
+	return _node.debugData ? _node.debugData->location : langutil::SourceLocation{};
+}
+
+/// Extracts the source location from a Yul node.
+template <class... Args> inline langutil::SourceLocation locationOf(std::variant<Args...> const& _node)
+{
+	return std::visit([](auto const& _arg) { return locationOf(_arg); }, _node);
 }
 
 struct DebugDataExtractor

libyul/CMakeLists.txt

@@ -68,9 +68,11 @@ add_library(yul
 	backends/evm/EVMMetrics.h
 	backends/evm/NoOutputAssembly.h
 	backends/evm/NoOutputAssembly.cpp
+	backends/evm/OptimizedEVMCodeTransform.cpp
+	backends/evm/OptimizedEVMCodeTransform.h
 	backends/evm/StackHelpers.h
-	backends/evm/StackLayoutGenerator.h
 	backends/evm/StackLayoutGenerator.cpp
+	backends/evm/StackLayoutGenerator.h
 	backends/evm/VariableReferenceCounter.h
 	backends/evm/VariableReferenceCounter.cpp
 	backends/wasm/EVMToEwasmTranslator.cpp

libyul/backends/evm/OptimizedEVMCodeTransform.cpp

@@ -0,0 +1,513 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+#include <libyul/backends/evm/OptimizedEVMCodeTransform.h>
+
+#include <libyul/backends/evm/ControlFlowGraphBuilder.h>
+#include <libyul/backends/evm/StackHelpers.h>
+#include <libyul/backends/evm/StackLayoutGenerator.h>
+
+#include <libyul/Utilities.h>
+
+#include <libsolutil/Visitor.h>
+#include <libsolutil/cxx20.h>
+
+#include <range/v3/view/drop.hpp>
+#include <range/v3/view/enumerate.hpp>
+#include <range/v3/view/filter.hpp>
+#include <range/v3/view/iota.hpp>
+#include <range/v3/view/map.hpp>
+#include <range/v3/view/reverse.hpp>
+#include <range/v3/view/take_last.hpp>
+
+using namespace solidity;
+using namespace solidity::yul;
+using namespace std;
+
+vector<StackTooDeepError> OptimizedEVMCodeTransform::run(
+	AbstractAssembly& _assembly,
+	AsmAnalysisInfo& _analysisInfo,
+	Block const& _block,
+	EVMDialect const& _dialect,
+	BuiltinContext& _builtinContext,
+	bool _useNamedLabelsForFunctions
+)
+{
+	std::unique_ptr<CFG> dfg = ControlFlowGraphBuilder::build(_analysisInfo, _dialect, _block);
+	StackLayout stackLayout = StackLayoutGenerator::run(*dfg);
+	OptimizedEVMCodeTransform optimizedCodeTransform(
+		_assembly,
+		_builtinContext,
+		_useNamedLabelsForFunctions,
+		*dfg,
+		stackLayout
+	);
+	// Create initial entry layout.
+	optimizedCodeTransform.createStackLayout(stackLayout.blockInfos.at(dfg->entry).entryLayout);
+	optimizedCodeTransform(*dfg->entry);
+	for (Scope::Function const* function: dfg->functions)
+		optimizedCodeTransform(dfg->functionInfo.at(function));
+	return move(optimizedCodeTransform.m_stackErrors);
+}
+
+void OptimizedEVMCodeTransform::operator()(CFG::FunctionCall const& _call)
+{
+	// Validate stack.
+	{
+		yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+		yulAssert(m_stack.size() >= _call.function.get().arguments.size() + 1, "");
+		// Assert that we got the correct arguments on stack for the call.
+		for (auto&& [arg, slot]: ranges::zip_view(
+			_call.functionCall.get().arguments | ranges::views::reverse,
+			m_stack | ranges::views::take_last(_call.functionCall.get().arguments.size())
+		))
+			validateSlot(slot, arg);
+		// Assert that we got the correct return label on stack.
+		auto const* returnLabelSlot = get_if<FunctionCallReturnLabelSlot>(
+			&m_stack.at(m_stack.size() - _call.functionCall.get().arguments.size() - 1)
+		);
+		yulAssert(returnLabelSlot && &returnLabelSlot->call.get() == &_call.functionCall.get(), "");
+	}
+
+	// Emit code.
+	{
+		m_assembly.setSourceLocation(locationOf(_call));
+		m_assembly.appendJumpTo(
+			getFunctionLabel(_call.function),
+			static_cast<int>(_call.function.get().returns.size() - _call.function.get().arguments.size()) - 1,
+			AbstractAssembly::JumpType::IntoFunction
+		);
+		m_assembly.appendLabel(m_returnLabels.at(&_call.functionCall.get()));
+	}
+
+	// Update stack.
+	{
+		// Remove arguments and return label from m_stack.
+		for (size_t i = 0; i < _call.function.get().arguments.size() + 1; ++i)
+			m_stack.pop_back();
+		// Push return values to m_stack.
+		for (size_t index: ranges::views::iota(0u, _call.function.get().returns.size()))
+			m_stack.emplace_back(TemporarySlot{_call.functionCall, index});
+		yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+	}
+}
+
+void OptimizedEVMCodeTransform::operator()(CFG::BuiltinCall const& _call)
+{
+	// Validate stack.
+	{
+		yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+		yulAssert(m_stack.size() >= _call.arguments, "");
+		// Assert that we got a correct stack for the call.
+		for (auto&& [arg, slot]: ranges::zip_view(
+			_call.functionCall.get().arguments |
+			ranges::views::enumerate |
+			ranges::views::filter(util::mapTuple([&](size_t idx, auto&) -> bool {
+				return !_call.builtin.get().literalArgument(idx);
+			})) |
+			ranges::views::reverse |
+			ranges::views::values,
+			m_stack | ranges::views::take_last(_call.arguments)
+		))
+			validateSlot(slot, arg);
+	}
+
+	// Emit code.
+	{
+		m_assembly.setSourceLocation(locationOf(_call));
+		static_cast<BuiltinFunctionForEVM const&>(_call.builtin.get()).generateCode(
+			_call.functionCall,
+			m_assembly,
+			m_builtinContext
+		);
+	}
+
+	// Update stack.
+	{
+		// Remove arguments from m_stack.
+		for (size_t i = 0; i < _call.arguments; ++i)
+			m_stack.pop_back();
+		// Push return values to m_stack.
+		for (size_t index: ranges::views::iota(0u, _call.builtin.get().returns.size()))
+			m_stack.emplace_back(TemporarySlot{_call.functionCall, index});
+		yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+	}
+}
+
+void OptimizedEVMCodeTransform::operator()(CFG::Assignment const& _assignment)
+{
+	yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+
+	// Invalidate occurrences of the assigned variables.
+	for (auto& currentSlot: m_stack)
+		if (VariableSlot const* varSlot = get_if<VariableSlot>(&currentSlot))
+			if (util::contains(_assignment.variables, *varSlot))
+				currentSlot = JunkSlot{};
+
+	// Assign variables to current stack top.
+	yulAssert(m_stack.size() >= _assignment.variables.size(), "");
+	for (auto&& [currentSlot, varSlot]: ranges::zip_view(
+		m_stack | ranges::views::take_last(_assignment.variables.size()),
+		_assignment.variables
+	))
+		currentSlot = varSlot;
+}
+
+OptimizedEVMCodeTransform::OptimizedEVMCodeTransform(
+	AbstractAssembly& _assembly,
+	BuiltinContext& _builtinContext,
+	bool _useNamedLabelsForFunctions,
+	CFG const& _dfg,
+	StackLayout const& _stackLayout
+):
+	m_assembly(_assembly),
+	m_builtinContext(_builtinContext),
+	m_useNamedLabelsForFunctions(_useNamedLabelsForFunctions),
+	m_dfg(_dfg),
+	m_stackLayout(_stackLayout)
+{
+}
+
+void OptimizedEVMCodeTransform::assertLayoutCompatibility(Stack const& _currentStack, Stack const& _desiredStack)
+{
+	yulAssert(_currentStack.size() == _desiredStack.size(), "");
+	for (auto&& [currentSlot, desiredSlot]: ranges::zip_view(_currentStack, _desiredStack))
+		yulAssert(holds_alternative<JunkSlot>(desiredSlot) || currentSlot == desiredSlot, "");
+}
+
+AbstractAssembly::LabelID OptimizedEVMCodeTransform::getFunctionLabel(Scope::Function const& _function)
+{
+	CFG::FunctionInfo const& functionInfo = m_dfg.functionInfo.at(&_function);
+	if (!m_functionLabels.count(&functionInfo))
+		m_functionLabels[&functionInfo] = m_useNamedLabelsForFunctions ? m_assembly.namedLabel(
+			functionInfo.function.name.str(),
+			functionInfo.function.arguments.size(),
+			functionInfo.function.returns.size(),
+			{}
+		) : m_assembly.newLabelId();
+	return m_functionLabels[&functionInfo];
+}
+
+void OptimizedEVMCodeTransform::validateSlot(StackSlot const& _slot, Expression const& _expression)
+{
+	std::visit(util::GenericVisitor{
+		[&](yul::Literal const& _literal) {
+			auto* literalSlot = get_if<LiteralSlot>(&_slot);
+			yulAssert(literalSlot && valueOfLiteral(_literal) == literalSlot->value, "");
+		},
+		[&](yul::Identifier const& _identifier) {
+			auto* variableSlot = get_if<VariableSlot>(&_slot);
+			yulAssert(variableSlot && variableSlot->variable.get().name == _identifier.name, "");
+		},
+		[&](yul::FunctionCall const& _call) {
+			auto* temporarySlot = get_if<TemporarySlot>(&_slot);
+			yulAssert(temporarySlot && &temporarySlot->call.get() == &_call && temporarySlot->index == 0, "");
+		}
+	}, _expression);
+}
+
+void OptimizedEVMCodeTransform::createStackLayout(Stack _targetStack)
+{
+	static constexpr auto slotVariableName = [](StackSlot const& _slot) {
+		return std::visit(util::GenericVisitor{
+			[](VariableSlot const& _var) { return _var.variable.get().name; },
+			[](auto const&) { return YulString{}; }
+		}, _slot);
+	};
+
+	yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+	// ::createStackLayout asserts that it has successfully achieved the target layout.
+	::createStackLayout(
+		m_stack,
+		_targetStack | ranges::to<Stack>,
+		// Swap callback.
+		[&](unsigned _i)
+		{
+			yulAssert(static_cast<int>(m_stack.size()) == m_assembly.stackHeight(), "");
+			yulAssert(_i > 0 && _i < m_stack.size(), "");
+			if (_i <= 16)
+				m_assembly.appendInstruction(evmasm::swapInstruction(_i));
+			else
+			{
+				int deficit = static_cast<int>(_i) - 16;
+				StackSlot const& deepSlot = m_stack.at(m_stack.size() - _i - 1);
+				YulString varNameDeep = slotVariableName(deepSlot);
+				YulString varNameTop = slotVariableName(m_stack.back());
+				string msg =
+					"Cannot swap " + (varNameDeep.empty() ? "Slot " + stackSlotToString(deepSlot) : "Variable " + varNameDeep.str()) +
+					" with " + (varNameTop.empty() ? "Slot " + stackSlotToString(m_stack.back()) : "Variable " + varNameTop.str()) +
+					": too deep in the stack by " + to_string(deficit) + " slots in " + stackToString(m_stack);
+				m_stackErrors.emplace_back(StackTooDeepError(
+					m_currentFunctionInfo ? m_currentFunctionInfo->function.name : YulString{},
+					varNameDeep.empty() ? varNameTop : varNameDeep,
+					deficit,
+					msg
+				));
+				m_assembly.markAsInvalid();
+			}
+		},
+		// Push or dup callback.
+		[&](StackSlot const& _slot)
+		{
+			yulAssert(static_cast<int>(m_stack.size()) == m_assembly.stackHeight(), "");
+
+			// Dup the slot, if already on stack and reachable.
+			if (auto depth = util::findOffset(m_stack | ranges::views::reverse, _slot))
+			{
+				if (*depth < 16)
+				{
+					m_assembly.appendInstruction(evmasm::dupInstruction(static_cast<unsigned>(*depth + 1)));
+					return;
+				}
+				else if (!canBeFreelyGenerated(_slot))
+				{
+					int deficit = static_cast<int>(*depth - 15);
+					YulString varName = slotVariableName(_slot);
+					string msg =
+						(varName.empty() ? "Slot " + stackSlotToString(_slot) : "Variable " + varName.str())
+						+ " is " + to_string(*depth - 15) + " too deep in the stack " + stackToString(m_stack);
+					m_stackErrors.emplace_back(StackTooDeepError(
+						m_currentFunctionInfo ? m_currentFunctionInfo->function.name : YulString{},
+						varName,
+						deficit,
+						msg
+					));
+					m_assembly.markAsInvalid();
+					m_assembly.appendConstant(u256(0xCAFFEE));
+					return;
+				}
+				// else: the slot is too deep in stack, but can be freely generated, we fall through to push it again.
+			}
+
+			// The slot can be freely generated or is an unassigned return variable. Push it.
+			std::visit(util::GenericVisitor{
+				[&](LiteralSlot const& _literal)
+				{
+					m_assembly.setSourceLocation(locationOf(_literal));
+					m_assembly.appendConstant(_literal.value);
+				},
+				[&](FunctionReturnLabelSlot const&)
+				{
+					yulAssert(false, "Cannot produce function return label.");
+				},
+				[&](FunctionCallReturnLabelSlot const& _returnLabel)
+				{
+					if (!m_returnLabels.count(&_returnLabel.call.get()))
+						m_returnLabels[&_returnLabel.call.get()] = m_assembly.newLabelId();
+					m_assembly.setSourceLocation(locationOf(_returnLabel.call.get()));
+					m_assembly.appendLabelReference(m_returnLabels.at(&_returnLabel.call.get()));
+				},
+				[&](VariableSlot const& _variable)
+				{
+					if (m_currentFunctionInfo && util::contains(m_currentFunctionInfo->returnVariables, _variable))
+					{
+						m_assembly.setSourceLocation(locationOf(_variable));
+						m_assembly.appendConstant(0);
+						return;
+					}
+					yulAssert(false, "Variable not found on stack.");
+				},
+				[&](TemporarySlot const&)
+				{
+					yulAssert(false, "Function call result requested, but not found on stack.");
+				},
+				[&](JunkSlot const&)
+				{
+					// Note: this will always be popped, so we can push anything.
+					m_assembly.appendInstruction(evmasm::Instruction::CODESIZE);
+				}
+			}, _slot);
+		},
+		// Pop callback.
+		[&]()
+		{
+			m_assembly.appendInstruction(evmasm::Instruction::POP);
+		}
+	);
+	yulAssert(m_assembly.stackHeight() == static_cast<int>(m_stack.size()), "");
+}
+
+void OptimizedEVMCodeTransform::operator()(CFG::BasicBlock const& _block)
+{
+	// Assert that this is the first visit of the block and mark as generated.
+	yulAssert(m_generated.insert(&_block).second, "");
+
+	auto const& blockInfo = m_stackLayout.blockInfos.at(&_block);
+
+	// Assert that the stack is valid for entering the block.
+	assertLayoutCompatibility(m_stack, blockInfo.entryLayout);
+	m_stack = blockInfo.entryLayout; // Might set some slots to junk, if not required by the block.
+	yulAssert(static_cast<int>(m_stack.size()) == m_assembly.stackHeight(), "");
+
+	// Emit jump label, if required.
+	if (auto label = util::valueOrNullptr(m_blockLabels, &_block))
+		m_assembly.appendLabel(*label);
+
+	for (auto const& operation: _block.operations)
+	{
+		// Create required layout for entering the operation.
+		createStackLayout(m_stackLayout.operationEntryLayout.at(&operation));
+
+		// Assert that we have the inputs of the operation on stack top.
+		yulAssert(static_cast<int>(m_stack.size()) == m_assembly.stackHeight(), "");
+		yulAssert(m_stack.size() >= operation.input.size(), "");
+		size_t baseHeight = m_stack.size() - operation.input.size();
+		assertLayoutCompatibility(
+			m_stack | ranges::views::take_last(operation.input.size()) | ranges::to<Stack>,
+			operation.input
+		);
+
+		// Perform the operation.
+		std::visit(*this, operation.operation);
+
+		// Assert that the operation produced its proclaimed output.
+		yulAssert(static_cast<int>(m_stack.size()) == m_assembly.stackHeight(), "");
+		yulAssert(m_stack.size() == baseHeight + operation.output.size(), "");
+		yulAssert(m_stack.size() >= operation.output.size(), "");
+		assertLayoutCompatibility(
+			m_stack | ranges::views::take_last(operation.output.size()) | ranges::to<Stack>,
+			operation.output
+		);
+	}
+
+	// Exit the block.
+	std::visit(util::GenericVisitor{
+		[&](CFG::BasicBlock::MainExit const&)
+		{
+			m_assembly.appendInstruction(evmasm::Instruction::STOP);
+		},
+		[&](CFG::BasicBlock::Jump const& _jump)
+		{
+			// Create the stack expected at the jump target.
+			createStackLayout(m_stackLayout.blockInfos.at(_jump.target).entryLayout);
+
+			// If this is the only jump to the block, we do not need a label and can directly continue with the target block.
+			if (!m_blockLabels.count(_jump.target) && _jump.target->entries.size() == 1)
+			{
+				yulAssert(!_jump.backwards, "");
+				(*this)(*_jump.target);
+			}
+			else
+			{
+				// Generate a jump label for the target, if not already present.
+				if (!m_blockLabels.count(_jump.target))
+					m_blockLabels[_jump.target] = m_assembly.newLabelId();
+
+				// If we already have generated the target block, jump to it, otherwise generate it in place.
+				if (m_generated.count(_jump.target))
+					m_assembly.appendJumpTo(m_blockLabels[_jump.target]);
+				else
+					(*this)(*_jump.target);
+			}
+		},
+		[&](CFG::BasicBlock::ConditionalJump const& _conditionalJump)
+		{
+			// Create the shared entry layout of the jump targets, which is stored as exit layout of the current block.
+			createStackLayout(blockInfo.exitLayout);
+
+			// Create labels for the targets, if not already present.
+			if (!m_blockLabels.count(_conditionalJump.nonZero))
+				m_blockLabels[_conditionalJump.nonZero] = m_assembly.newLabelId();
+			if (!m_blockLabels.count(_conditionalJump.zero))
+				m_blockLabels[_conditionalJump.zero] = m_assembly.newLabelId();
+
+			// Assert that we have the correct condition on stack.
+			yulAssert(!m_stack.empty(), "");
+			yulAssert(m_stack.back() == _conditionalJump.condition, "");
+
+			// Emit the conditional jump to the non-zero label and update the stored stack.
+			m_assembly.appendJumpToIf(m_blockLabels[_conditionalJump.nonZero]);
+			m_stack.pop_back();
+
+			// Assert that we have a valid stack for both jump targets.
+			assertLayoutCompatibility(m_stack, m_stackLayout.blockInfos.at(_conditionalJump.nonZero).entryLayout);
+			assertLayoutCompatibility(m_stack, m_stackLayout.blockInfos.at(_conditionalJump.zero).entryLayout);
+
+			{
+				// Restore the stack afterwards for the non-zero case below.
+				ScopeGuard stackRestore([storedStack = m_stack, this]() {
+					m_stack = move(storedStack);
+					m_assembly.setStackHeight(static_cast<int>(m_stack.size()));
+				});
+
+				// If we have already generated the zero case, jump to it, otherwise generate it in place.
+				if (m_generated.count(_conditionalJump.zero))
+					m_assembly.appendJumpTo(m_blockLabels[_conditionalJump.zero]);
+				else
+					(*this)(*_conditionalJump.zero);
+			}
+			// Note that each block visit terminates control flow, so we cannot fall through from the zero case.
+
+			// Generate the non-zero block, if not done already.
+			if (!m_generated.count(_conditionalJump.nonZero))
+				(*this)(*_conditionalJump.nonZero);
+		},
+		[&](CFG::BasicBlock::FunctionReturn const& _functionReturn)
+		{
+			yulAssert(m_currentFunctionInfo, "");
+			yulAssert(m_currentFunctionInfo == _functionReturn.info, "");
+
+			// Construct the function return layout, which is fully determined by the function signature.
+			Stack exitStack = m_currentFunctionInfo->returnVariables | ranges::views::transform([](auto const& _varSlot){
+				return StackSlot{_varSlot};
+			}) | ranges::to<Stack>;
+			exitStack.emplace_back(FunctionReturnLabelSlot{_functionReturn.info->function});
+
+			// Create the function return layout and jump.
+			m_assembly.setSourceLocation(locationOf(*m_currentFunctionInfo));
+			createStackLayout(exitStack);
+			m_assembly.setSourceLocation(locationOf(*m_currentFunctionInfo));
+			m_assembly.appendJump(0, AbstractAssembly::JumpType::OutOfFunction);
+		},
+		[&](CFG::BasicBlock::Terminated const&)
+		{
+			// Assert that the last builtin call was in fact terminating.
+			yulAssert(!_block.operations.empty(), "");
+			CFG::BuiltinCall const* builtinCall = get_if<CFG::BuiltinCall>(&_block.operations.back().operation);
+			yulAssert(builtinCall, "");
+			yulAssert(builtinCall->builtin.get().controlFlowSideEffects.terminates, "");
+		}
+	}, _block.exit);
+	// TODO: We could assert that the last emitted assembly item terminated or was an (unconditional) jump.
+	//       But currently AbstractAssembly does not allow peeking at the last emitted assembly item.
+	m_stack.clear();
+	m_assembly.setStackHeight(0);
+}
+
+void OptimizedEVMCodeTransform::operator()(CFG::FunctionInfo const& _functionInfo)
+{
+	yulAssert(!m_currentFunctionInfo, "");
+	ScopedSaveAndRestore currentFunctionInfoRestore(m_currentFunctionInfo, &_functionInfo);
+
+	yulAssert(m_stack.empty() && m_assembly.stackHeight() == 0, "");
+
+	// Create function entry layout in m_stack.
+	m_stack.emplace_back(FunctionReturnLabelSlot{_functionInfo.function});
+	for (auto const& param: _functionInfo.parameters | ranges::views::reverse)
+		m_stack.emplace_back(param);
+	m_assembly.setStackHeight(static_cast<int>(m_stack.size()));
+
+	m_assembly.setSourceLocation(locationOf(_functionInfo));
+	m_assembly.appendLabel(getFunctionLabel(_functionInfo.function));
+
+	// Create the entry layout of the function body block and visit.
+	createStackLayout(m_stackLayout.blockInfos.at(_functionInfo.entry).entryLayout);
+	(*this)(*_functionInfo.entry);
+
+	m_stack.clear();
+	m_assembly.setStackHeight(0);
+}

libyul/backends/evm/OptimizedEVMCodeTransform.h

@@ -0,0 +1,110 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+/**
+ * Code generator for translating Yul / inline assembly to EVM.
+ */
+
+#pragma once
+
+#include <libyul/AST.h>
+#include <libyul/backends/evm/EVMDialect.h>
+#include <libyul/backends/evm/ControlFlowGraph.h>
+#include <libyul/Exceptions.h>
+#include <libyul/Scope.h>
+
+#include <optional>
+#include <stack>
+
+namespace solidity::langutil
+{
+class ErrorReporter;
+}
+
+namespace solidity::yul
+{
+struct AsmAnalysisInfo;
+struct StackLayout;
+
+class OptimizedEVMCodeTransform
+{
+public:
+	[[nodiscard]] static std::vector<StackTooDeepError> run(
+		AbstractAssembly& _assembly,
+		AsmAnalysisInfo& _analysisInfo,
+		Block const& _block,
+		EVMDialect const& _dialect,
+		BuiltinContext& _builtinContext,
+		bool _useNamedLabelsForFunctions = false
+	);
+
+	/// Generate code for the function call @a _call. Only public for using with std::visit.
+	void operator()(CFG::FunctionCall const& _call);
+	/// Generate code for the builtin call @a _call. Only public for using with std::visit.
+	void operator()(CFG::BuiltinCall const& _call);
+	/// Generate code for the assignment @a _assignment. Only public for using with std::visit.
+	void operator()(CFG::Assignment const& _assignment);
+private:
+	OptimizedEVMCodeTransform(
+		AbstractAssembly& _assembly,
+		BuiltinContext& _builtinContext,
+		bool _useNamedLabelsForFunctions,
+		CFG const& _dfg,
+		StackLayout const& _stackLayout
+	);
+
+	/// Assert that it is valid to transition from @a _currentStack to @a _desiredStack.
+	/// That is @a _currentStack matches each slot in @a _desiredStack that is not a JunkSlot exactly.
+	static void assertLayoutCompatibility(Stack const& _currentStack, Stack const& _desiredStack);
+	/// @returns The label of the entry point of the given @a _function.
+	/// Creates and stores a new label, if none exists already.
+	AbstractAssembly::LabelID getFunctionLabel(Scope::Function const& _function);
+	/// Assert that @a _slot contains the value of @a _expression.
+	static void validateSlot(StackSlot const& _slot, Expression const& _expression);
+
+	/// Shuffles m_stack to the desired @a _targetStack while emitting the shuffling code to m_assembly.
+	void createStackLayout(Stack _targetStack);
+
+	/// Generate code for the given block @a _block.
+	/// Expects the current stack layout m_stack to be a stack layout that is compatible with the
+	/// entry layout expected by the block.
+	/// Recursively generates code for blocks that are jumped to.
+	/// The last emitted assembly instruction is always an unconditional jump or terminating.
+	/// Always exits with an empty stack layout.
+	void operator()(CFG::BasicBlock const& _block);
+
+	/// Generate code for the given function.
+	/// Resets m_stack.
+	void operator()(CFG::FunctionInfo const& _functionInfo);
+
+	AbstractAssembly& m_assembly;
+	BuiltinContext& m_builtinContext;
+	bool m_useNamedLabelsForFunctions = true;
+	CFG const& m_dfg;
+	StackLayout const& m_stackLayout;
+	Stack m_stack;
+	std::map<yul::FunctionCall const*, AbstractAssembly::LabelID> m_returnLabels;
+	std::map<CFG::BasicBlock const*, AbstractAssembly::LabelID> m_blockLabels;
+	std::map<CFG::FunctionInfo const*, AbstractAssembly::LabelID> m_functionLabels;
+	/// Set of blocks already generated. If any of the contained blocks is ever jumped to, m_blockLabels should
+	/// contain a jump label for it.
+	std::set<CFG::BasicBlock const*> m_generated;
+	CFG::FunctionInfo const* m_currentFunctionInfo = nullptr;
+	std::vector<StackTooDeepError> m_stackErrors;
+};
+
+}