Yul codegen for immutables.

docs/yul.rst

@@ -885,13 +885,6 @@ the ``dup`` and ``swap`` instructions as well as ``jump`` instructions, labels a
 | gaslimit()              |     | F | block gas limit of the current block                            |
 +-------------------------+-----+---+-----------------------------------------------------------------+
 
-There are three additional functions, ``datasize(x)``, ``dataoffset(x)`` and ``datacopy(t, f, l)``,
-which are used to access other parts of a Yul object.
-
-``datasize`` and ``dataoffset`` can only take string literals (the names of other objects)
-as arguments and return the size and offset in the data area, respectively.
-For the EVM, the ``datacopy`` function is equivalent to ``codecopy``.
-
 .. _yul-call-return-area:
 
 .. note::
@@ -903,6 +896,32 @@ For the EVM, the ``datacopy`` function is equivalent to ``codecopy``.
   The remaining bytes will retain their values as of before the call. If the call fails (it returns ``0``),
   nothing is written to that area, but you can still retrieve the failure data using ``returndatacopy``.
 
+
+In some internal dialects, there are additional functions:
+
+datasize, dataoffset, datacopy
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The functions ``datasize(x)``, ``dataoffset(x)`` and ``datacopy(t, f, l)``,
+are used to access other parts of a Yul object.
+
+``datasize`` and ``dataoffset`` can only take string literals (the names of other objects)
+as arguments and return the size and offset in the data area, respectively.
+For the EVM, the ``datacopy`` function is equivalent to ``codecopy``.
+
+
+setimmutable, loadimmutable
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The functions ``setimmutable("name", value)`` and ``loadimmutable("name")`` are
+used for the immutable mechanism in Solidity and do not nicely map to pur Yul.
+The function ``setimmutable`` assumes that the runtime code of a contract
+is currently copied to memory at offsot zero. The call to ``setimmutable("name", value)``
+will store ``value`` at all points in memory that contain a call to
+``loadimmutable("name")``.
+
+
+
 .. _yul-object:
 
 Specification of Yul Object

libsolidity/codegen/ir/IRGenerationContext.cpp

@@ -22,6 +22,7 @@
 
 #include <libsolidity/codegen/YulUtilFunctions.h>
 #include <libsolidity/codegen/ABIFunctions.h>
+#include <libsolidity/codegen/CompilerUtils.h>
 #include <libsolidity/ast/AST.h>
 #include <libsolidity/ast/TypeProvider.h>
 
@@ -76,6 +77,36 @@ IRVariable const& IRGenerationContext::localVariable(VariableDeclaration const&
 	return m_localVariables.at(&_varDecl);
 }
 
+void IRGenerationContext::registerImmutableVariable(VariableDeclaration const& _variable)
+{
+	solAssert(_variable.immutable(), "Attempted to register a non-immutable variable as immutable.");
+	solUnimplementedAssert(
+		_variable.annotation().type->isValueType(),
+		"Only immutable variables of value type are supported."
+	);
+	solAssert(m_reservedMemory.has_value(), "Reserved memory has already been reset.");
+	m_immutableVariables[&_variable] = CompilerUtils::generalPurposeMemoryStart + *m_reservedMemory;
+	solAssert(_variable.annotation().type->memoryHeadSize() == 32, "Memory writes might overlap.");
+	*m_reservedMemory += _variable.annotation().type->memoryHeadSize();
+}
+
+size_t IRGenerationContext::immutableMemoryOffset(VariableDeclaration const& _variable) const
+{
+	solAssert(
+		m_immutableVariables.count(&_variable),
+		"Unknown immutable variable: " + _variable.name()
+	);
+	return m_immutableVariables.at(&_variable);
+}
+
+size_t IRGenerationContext::reservedMemory()
+{
+	solAssert(m_reservedMemory.has_value(), "Reserved memory was used before.");
+	size_t reservedMemory = *m_reservedMemory;
+	m_reservedMemory = std::nullopt;
+	return reservedMemory;
+}
+
 void IRGenerationContext::addStateVariable(
 	VariableDeclaration const& _declaration,
 	u256 _storageOffset,

libsolidity/codegen/ir/IRGenerationContext.h

@@ -81,6 +81,17 @@ class IRGenerationContext
 	bool isLocalVariable(VariableDeclaration const& _varDecl) const { return m_localVariables.count(&_varDecl); }
 	IRVariable const& localVariable(VariableDeclaration const& _varDecl);
 
+	/// Registers an immutable variable of the contract.
+	/// Should only be called at construction time.
+	void registerImmutableVariable(VariableDeclaration const& _varDecl);
+	/// @returns the reserved memory for storing the value of the
+	/// immutable @a _variable during contract creation.
+	size_t immutableMemoryOffset(VariableDeclaration const& _variable) const;
+	/// @returns the reserved memory and resets it to mark it as used.
+	/// Intended to be used only once for initializing the free memory pointer
+	/// to after the area used for immutables.
+	size_t reservedMemory();
+
 	void addStateVariable(VariableDeclaration const& _varDecl, u256 _storageOffset, unsigned _byteOffset);
 	bool isStateVariable(VariableDeclaration const& _varDecl) const { return m_stateVariables.count(&_varDecl); }
 	std::pair<u256, unsigned> storageLocationOfVariable(VariableDeclaration const& _varDecl) const
@@ -123,6 +134,12 @@ class IRGenerationContext
 	OptimiserSettings m_optimiserSettings;
 	ContractDefinition const* m_mostDerivedContract = nullptr;
 	std::map<VariableDeclaration const*, IRVariable> m_localVariables;
+	/// Memory offsets reserved for the values of immutable variables during contract creation.
+	/// This map is empty in the runtime context.
+	std::map<VariableDeclaration const*, size_t> m_immutableVariables;
+	/// Total amount of reserved memory. Reserved memory is used to store
+	/// immutable variables during contract creation.
+	std::optional<size_t> m_reservedMemory = {0};
 	/// Storage offsets of state variables
 	std::map<VariableDeclaration const*, std::pair<u256, unsigned>> m_stateVariables;
 	MultiUseYulFunctionCollector m_functions;

libsolidity/codegen/ir/IRGenerator.cpp

@@ -114,6 +114,8 @@ string IRGenerator::generate(
 	)");
 
 	resetContext(_contract);
+	for (VariableDeclaration const* var: ContractType(_contract).immutableVariables())
+		m_context.registerImmutableVariable(*var);
 
 	t("CreationObject", m_context.creationObjectName(_contract));
 	t("memoryInit", memoryInit());
@@ -142,6 +144,7 @@ string IRGenerator::generate(
 	t("subObjects", subObjectSources(m_context.subObjectsCreated()));
 
 	resetContext(_contract);
+	// Do not register immutables to avoid assignment.
 	t("RuntimeObject", m_context.runtimeObjectName(_contract));
 	t("dispatch", dispatchRoutine(_contract));
 	generateQueuedFunctions();
@@ -200,7 +203,6 @@ string IRGenerator::generateGetter(VariableDeclaration const& _varDecl)
 	Type const* type = _varDecl.annotation().type;
 
 	solAssert(!_varDecl.isConstant(), "");
-	solAssert(!_varDecl.immutable(), "");
 	solAssert(_varDecl.isStateVariable(), "");
 
 	if (auto const* mappingType = dynamic_cast<MappingType const*>(type))
@@ -254,17 +256,32 @@ string IRGenerator::generateGetter(VariableDeclaration const& _varDecl)
 		solUnimplementedAssert(type->isValueType(), "");
 
 		return m_context.functionCollector().createFunction(functionName, [&]() {
-			pair<u256, unsigned> slot_offset = m_context.storageLocationOfVariable(_varDecl);
-
-			return Whiskers(R"(
-				function <functionName>() -> rval {
-					rval := <readStorage>(<slot>)
-				}
-			)")
-			("functionName", functionName)
-			("readStorage", m_utils.readFromStorage(*type, slot_offset.second, false))
-			("slot", slot_offset.first.str())
-			.render();
+			if (_varDecl.immutable())
+			{
+				solUnimplementedAssert(type->sizeOnStack() == 1, "");
+				return Whiskers(R"(
+					function <functionName>() -> rval {
+						rval := loadimmutable("<id>")
+					}
+				)")
+				("functionName", functionName)
+				("id", to_string(_varDecl.id()))
+				.render();
+			}
+			else
+			{
+				pair<u256, unsigned> slot_offset = m_context.storageLocationOfVariable(_varDecl);
+
+				return Whiskers(R"(
+					function <functionName>() -> rval {
+						rval := <readStorage>(<slot>)
+					}
+				)")
+				("functionName", functionName)
+				("readStorage", m_utils.readFromStorage(*type, slot_offset.second, false))
+				("slot", slot_offset.first.str())
+				.render();
+			}
 		});
 	}
 }
@@ -325,7 +342,7 @@ string IRGenerator::initStateVariables(ContractDefinition const& _contract)
 {
 	IRGeneratorForStatements generator{m_context, m_utils};
 	for (VariableDeclaration const* variable: _contract.stateVariables())
-		if (!variable->isConstant() && !variable->immutable())
+		if (!variable->isConstant())
 			generator.initializeStateVar(*variable);
 
 	return generator.code();
@@ -391,10 +408,41 @@ void IRGenerator::generateImplicitConstructors(ContractDefinition const& _contra
 string IRGenerator::deployCode(ContractDefinition const& _contract)
 {
 	Whiskers t(R"X(
+		<#loadImmutables>
+			let <var> := mload(<memoryOffset>)
+		</loadImmutables>
+
 		codecopy(0, dataoffset("<object>"), datasize("<object>"))
+
+		<#storeImmutables>
+			setimmutable("<immutableName>", <var>)
+		</storeImmutables>
+
 		return(0, datasize("<object>"))
 	)X");
 	t("object", m_context.runtimeObjectName(_contract));
+
+	vector<map<string, string>> loadImmutables;
+	vector<map<string, string>> storeImmutables;
+
+	for (VariableDeclaration const* immutable: ContractType(_contract).immutableVariables())
+	{
+		solUnimplementedAssert(immutable->type()->isValueType(), "");
+		solUnimplementedAssert(immutable->type()->sizeOnStack() == 1, "");
+		string yulVar = m_context.newYulVariable();
+		loadImmutables.emplace_back(map<string, string>{
+			{"var"s, yulVar},
+			{"memoryOffset"s, to_string(m_context.immutableMemoryOffset(*immutable))}
+		});
+		storeImmutables.emplace_back(map<string, string>{
+			{"var"s, yulVar},
+			{"immutableName"s, to_string(immutable->id())}
+		});
+	}
+	t("loadImmutables", std::move(loadImmutables));
+	// reverse order to ease stack strain
+	reverse(storeImmutables.begin(), storeImmutables.end());
+	t("storeImmutables", std::move(storeImmutables));
 	return t.render();
 }
 
@@ -489,9 +537,9 @@ string IRGenerator::memoryInit()
 	// and thus can assume all memory to be zero, including the contents of
 	// the "zero memory area" (the position CompilerUtils::zeroPointer points to).
 	return
-		Whiskers{"mstore(<memPtr>, <generalPurposeStart>)"}
+		Whiskers{"mstore(<memPtr>, <freeMemoryStart>)"}
 		("memPtr", to_string(CompilerUtils::freeMemoryPointer))
-		("generalPurposeStart", to_string(CompilerUtils::generalPurposeMemoryStart))
+		("freeMemoryStart", to_string(CompilerUtils::generalPurposeMemoryStart + m_context.reservedMemory()))
 		.render();
 }
 

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -140,20 +140,21 @@ string IRGeneratorForStatements::code() const
 
 void IRGeneratorForStatements::initializeStateVar(VariableDeclaration const& _varDecl)
 {
-	solAssert(m_context.isStateVariable(_varDecl), "Must be a state variable.");
+	solAssert(_varDecl.immutable() || m_context.isStateVariable(_varDecl), "Must be immutable or a state variable.");
 	solAssert(!_varDecl.isConstant(), "");
-	solAssert(!_varDecl.immutable(), "");
-	if (_varDecl.value())
-	{
-		_varDecl.value()->accept(*this);
-		writeToLValue(IRLValue{
-			*_varDecl.annotation().type,
-			IRLValue::Storage{
-				util::toCompactHexWithPrefix(m_context.storageLocationOfVariable(_varDecl).first),
-				m_context.storageLocationOfVariable(_varDecl).second
-			}
-		}, *_varDecl.value());
-	}
+	if (!_varDecl.value())
+		return;
+
+	_varDecl.value()->accept(*this);
+	writeToLValue(
+		_varDecl.immutable() ?
+		IRLValue{*_varDecl.annotation().type, IRLValue::Immutable{&_varDecl}} :
+		IRLValue{*_varDecl.annotation().type, IRLValue::Storage{
+			util::toCompactHexWithPrefix(m_context.storageLocationOfVariable(_varDecl).first),
+			m_context.storageLocationOfVariable(_varDecl).second
+		}},
+		*_varDecl.value()
+	);
 }
 
 void IRGeneratorForStatements::initializeLocalVar(VariableDeclaration const& _varDecl)
@@ -1517,8 +1518,12 @@ void IRGeneratorForStatements::handleVariableReference(
 	// If the value is visited twice, `defineExpression` is called twice on
 	// the same expression.
 	solUnimplementedAssert(!_variable.isConstant(), "");
-	solUnimplementedAssert(!_variable.immutable(), "");
-	if (m_context.isLocalVariable(_variable))
+	if (_variable.isStateVariable() && _variable.immutable())
+		setLValue(_referencingExpression, IRLValue{
+			*_variable.annotation().type,
+			IRLValue::Immutable{&_variable}
+		});
+	else if (m_context.isLocalVariable(_variable))
 		setLValue(_referencingExpression, IRLValue{
 			*_variable.annotation().type,
 			IRLValue::Stack{m_context.localVariable(_variable)}
@@ -1939,6 +1944,18 @@ void IRGeneratorForStatements::writeToLValue(IRLValue const& _lvalue, IRVariable
 				}
 			},
 			[&](IRLValue::Stack const& _stack) { assign(_stack.variable, _value); },
+			[&](IRLValue::Immutable const& _immutable)
+			{
+				solUnimplementedAssert(_lvalue.type.isValueType(), "");
+				solUnimplementedAssert(_lvalue.type.sizeOnStack() == 1, "");
+				solAssert(_lvalue.type == *_immutable.variable->type(), "");
+				size_t memOffset = m_context.immutableMemoryOffset(*_immutable.variable);
+
+				IRVariable prepared(m_context.newYulVariable(), _lvalue.type);
+				define(prepared, _value);
+
+				m_code << "mstore(" << to_string(memOffset) << ", " << prepared.commaSeparatedList() << ")\n";
+			},
 			[&](IRLValue::Tuple const& _tuple) {
 				auto components = std::move(_tuple.components);
 				for (size_t i = 0; i < components.size(); i++)
@@ -1994,6 +2011,12 @@ IRVariable IRGeneratorForStatements::readFromLValue(IRLValue const& _lvalue)
 		[&](IRLValue::Stack const& _stack) {
 			define(result, _stack.variable);
 		},
+		[&](IRLValue::Immutable const& _immutable) {
+			solUnimplementedAssert(_lvalue.type.isValueType(), "");
+			solUnimplementedAssert(_lvalue.type.sizeOnStack() == 1, "");
+			solAssert(_lvalue.type == *_immutable.variable->type(), "");
+			define(result) << "loadimmutable(\"" << to_string(_immutable.variable->id()) << "\")\n";
+		},
 		[&](IRLValue::Tuple const&) {
 			solAssert(false, "Attempted to read from tuple lvalue.");
 		}

libsolidity/codegen/ir/IRLValue.h

@@ -35,6 +35,10 @@ struct IRLValue
 	{
 		IRVariable variable;
 	};
+	struct Immutable
+	{
+		VariableDeclaration const* variable = nullptr;
+	};
 	struct Storage
 	{
 		std::string const slot;
@@ -59,7 +63,7 @@ struct IRLValue
 	{
 		std::vector<std::optional<IRLValue>> components;
 	};
-	std::variant<Stack, Storage, Memory, Tuple> kind;
+	std::variant<Stack, Immutable, Storage, Memory, Tuple> kind;
 };
 
-}
+}

libyul/AsmAnalysis.cpp

@@ -306,11 +306,15 @@ vector<YulString> AsmAnalyzer::operator()(FunctionCall const& _funCall)
 					_funCall.functionName.location,
 					"Function expects direct literals as arguments."
 				);
-			else if (!m_dataNames.count(std::get<Literal>(arg).value))
-				typeError(
-					_funCall.functionName.location,
-					"Unknown data object \"" + std::get<Literal>(arg).value.str() + "\"."
-				);
+			else if (
+				_funCall.functionName.name.str() == "datasize" ||
+				_funCall.functionName.name.str() == "dataoffset"
+			)
+				if (!m_dataNames.count(std::get<Literal>(arg).value))
+					typeError(
+						_funCall.functionName.location,
+						"Unknown data object \"" + std::get<Literal>(arg).value.str() + "\"."
+					);
 		}
 	}
 	std::reverse(argTypes.begin(), argTypes.end());

libyul/backends/evm/AbstractAssembly.h

@@ -105,6 +105,11 @@ class AbstractAssembly
 	virtual void appendDataSize(SubID _sub) = 0;
 	/// Appends the given data to the assembly and returns its ID.
 	virtual SubID appendData(bytes const& _data) = 0;
+
+	/// Appends loading an immutable variable.
+	virtual void appendImmutable(std::string const& _identifier) = 0;
+	/// Appends an assignment to an immutable variable.
+	virtual void appendImmutableAssignment(std::string const& _identifier) = 0;
 };
 
 enum class IdentifierContext { LValue, RValue, VariableDeclaration };