[Sol->Yul] Implement .length for storage arrays

libsolidity/codegen/YulUtilFunctions.cpp

@@ -517,6 +517,120 @@ string YulUtilFunctions::arrayLengthFunction(ArrayType const& _type)
 	});
 }
 
+std::string YulUtilFunctions::resizeDynamicArrayFunction(ArrayType const& _type)
+{
+	solAssert(_type.location() == DataLocation::Storage, "");
+	solAssert(_type.isDynamicallySized(), "");
+	solUnimplementedAssert(!_type.isByteArray(), "Byte Arrays not yet implemented!");
+	solUnimplementedAssert(_type.baseType()->isValueType(), "...");
+	solUnimplementedAssert(_type.baseType()->storageBytes() <= 32, "...");
+	solUnimplementedAssert(_type.baseType()->storageSize() == 1, "");
+
+	string functionName = "resize_array_" + _type.identifier();
+	return m_functionCollector->createFunction(functionName, [&]() {
+		return Whiskers(R"(
+			function <functionName>(array, newLen) {
+				if gt(newLen, <maxArrayLength>) {
+					invalid()
+				}
+
+				let oldLen := <fetchLength>(array)
+
+				// Store new length
+				sstore(array, newLen)
+
+				// Size was reduced, clear end of array
+				if lt(newLen, oldLen) {
+					let oldSlotCount := <convertToSize>(oldLen)
+					let newSlotCount := <convertToSize>(newLen)
+					let arrayDataStart := <dataPosition>(array)
+					let deleteStart := add(arrayDataStart, newSlotCount)
+					let deleteEnd := add(arrayDataStart, oldSlotCount)
+					<clearStorageRange>(deleteStart, deleteEnd)
+				}
+			})")
+			("functionName", functionName)
+			("fetchLength", arrayLengthFunction(_type))
+			("convertToSize", arrayConvertLengthToSize(_type))
+			("dataPosition", arrayDataAreaFunction(_type))
+			("clearStorageRange", clearStorageRangeFunction(*_type.baseType()))
+			("maxArrayLength", (u256(1) << 64).str())
+			.render();
+	});
+}
+
+string YulUtilFunctions::clearStorageRangeFunction(Type const& _type)
+{
+	string functionName = "clear_storage_range_" + _type.identifier();
+
+	solUnimplementedAssert(_type.isValueType(), "...");
+
+	return m_functionCollector->createFunction(functionName, [&]() {
+		return Whiskers(R"(
+			function <functionName>(start, end) {
+				for {} lt(start, end) { start := add(start, 1) }
+				{
+					sstore(start, 0)
+				}
+			}
+		)")
+		("functionName", functionName)
+		.render();
+	});
+}
+
+string YulUtilFunctions::arrayConvertLengthToSize(ArrayType const& _type)
+{
+	string functionName = "array_convert_length_to_size_" + _type.identifier();
+	return m_functionCollector->createFunction(functionName, [&]() {
+		Type const& baseType = *_type.baseType();
+
+		switch (_type.location())
+		{
+			case DataLocation::Storage:
+			{
+				unsigned const baseStorageBytes = baseType.storageBytes();
+				solAssert(baseStorageBytes > 0, "");
+				solAssert(32 / baseStorageBytes > 0, "");
+
+				return Whiskers(R"(
+					function <functionName>(length) -> size {
+						size := length
+						<?multiSlot>
+							size := <mul>(<storageSize>, length)
+						<!multiSlot>
+							// Number of slots rounded up
+							size := div(add(length, sub(<itemsPerSlot>, 1)), <itemsPerSlot>)
+						</multiSlot>
+					})")
+					("functionName", functionName)
+					("multiSlot", baseType.storageSize() > 1)
+					("itemsPerSlot", to_string(32 / baseStorageBytes))
+					("storageSize", baseType.storageSize().str())
+					("mul", overflowCheckedUIntMulFunction(TypeProvider::uint256()->numBits()))
+					.render();
+			}
+			case DataLocation::CallData: // fallthrough
+			case DataLocation::Memory:
+				return Whiskers(R"(
+					function <functionName>(length) -> size {
+						<?byteArray>
+							size := length
+						<!byteArray>
+							size := <mul>(length, <elementSize>)
+						</byteArray>
+					})")
+					("functionName", functionName)
+					("elementSize", _type.location() == DataLocation::Memory ? baseType.memoryHeadSize() : baseType.calldataEncodedSize())
+					("byteArray", _type.isByteArray())
+					("mul", overflowCheckedUIntMulFunction(TypeProvider::uint256()->numBits()))
+					.render();
+			default:
+				solAssert(false, "");
+		}
+
+	});
+}
 string YulUtilFunctions::arrayAllocationSizeFunction(ArrayType const& _type)
 {
 	solAssert(_type.dataStoredIn(DataLocation::Memory), "");

libsolidity/codegen/YulUtilFunctions.h

@@ -104,6 +104,22 @@ public:
 	std::string overflowCheckedUIntSubFunction();
 
 	std::string arrayLengthFunction(ArrayType const& _type);
+
+	/// @returns the name of a function that resizes a storage array
+	/// signature: (array, newLen)
+	std::string resizeDynamicArrayFunction(ArrayType const& _type);
+
+	/// @returns the name of a function that will clear the storage area given
+	/// by the start and end (exclusive) parameters (slots). Only works for value types.
+	/// signature: (start, end)
+	std::string clearStorageRangeFunction(Type const& _type);
+
+	/// Returns the name of a function that will convert a given length to the
+	/// size in memory (number of storage slots or calldata/memory bytes) it
+	/// will require.
+	/// signature: (length) -> size
+	std::string arrayConvertLengthToSize(ArrayType const& _type);
+
 	/// @returns the name of a function that computes the number of bytes required
 	/// to store an array in memory given its length (internally encoded, not ABI encoded).
 	/// The function reverts for too large lengths.

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -703,7 +703,35 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 	}
 	case Type::Category::Array:
 	{
-		solUnimplementedAssert(false, "");
+		auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.expression().annotation().type);
+
+		solAssert(member == "length", "");
+
+		if (!type.isDynamicallySized())
+			defineExpression(_memberAccess) << type.length() << "\n";
+		else
+			switch (type.location())
+			{
+			case DataLocation::CallData:
+				solUnimplementedAssert(false, "");
+				//m_context << Instruction::SWAP1 << Instruction::POP;
+				break;
+			case DataLocation::Storage:
+				setLValue(_memberAccess, make_unique<IRStorageArrayLength>(
+					m_context,
+					m_context.variable(_memberAccess.expression()),
+					*_memberAccess.annotation().type,
+					type
+				));
+
+				break;
+			case DataLocation::Memory:
+				solUnimplementedAssert(false, "");
+				//m_context << Instruction::MLOAD;
+				break;
+			}
+
+		break;
 	}
 	case Type::Category::FixedBytes:
 	{

libsolidity/codegen/ir/IRLValue.cpp

@@ -137,3 +137,31 @@ string IRStorageItem::setToZero() const
 {
 	solUnimplemented("Delete for storage location not yet implemented");
 }
+
+IRStorageArrayLength::IRStorageArrayLength(IRGenerationContext& _context, string _slot, Type const& _type, ArrayType const& _arrayType):
+	IRLValue(_context, &_type), m_arrayType(_arrayType), m_slot(move(_slot))
+{
+	solAssert(*m_type == *TypeProvider::uint256(), "Must be uint256!");
+}
+
+string IRStorageArrayLength::retrieveValue() const
+{
+	return m_context.utils().arrayLengthFunction(m_arrayType) + "(" + m_slot + ")\n";
+}
+
+string IRStorageArrayLength::storeValue(std::string const& _value, Type const& _type) const
+{
+	solAssert(_type == *m_type, "Different type, but might not be an error.");
+
+	return m_context.utils().resizeDynamicArrayFunction(m_arrayType) +
+		"(" +
+		m_slot +
+		", " +
+		_value +
+		")\n";
+}
+
+string IRStorageArrayLength::setToZero() const
+{
+	return storeValue("0", *TypeProvider::uint256());
+}

libsolidity/codegen/ir/IRLValue.h

@@ -34,6 +34,7 @@ namespace solidity
 class VariableDeclaration;
 class IRGenerationContext;
 class Type;
+class ArrayType;
 
 /**
  * Abstract class used to retrieve, delete and store data in LValues.
@@ -107,6 +108,24 @@ private:
 	boost::variant<std::string, unsigned> const m_offset;
 };
 
+/**
+ * Reference to the "length" member of a dynamically-sized storage array. This is an LValue with special
+ * semantics since assignments to it might reduce its length and thus the array's members have to be
+ * deleted.
+ */
+class IRStorageArrayLength: public IRLValue
+{
+public:
+	IRStorageArrayLength(IRGenerationContext& _context, std::string _slot, Type const& _type, ArrayType const& _arrayType);
+
+	std::string retrieveValue() const override;
+	std::string storeValue(std::string const& _value, Type const& _type) const override;
+	std::string setToZero() const override;
+
+private:
+	ArrayType const& m_arrayType;
+	std::string const m_slot;
+};
 
 }
 }

test/libsolidity/semanticTests/viaYul/array_storage_length_access.sol

@@ -0,0 +1,19 @@
+contract C {
+	uint[] storageArray;
+	function set_get_length(uint256 len) public returns (uint256)
+	{
+		storageArray.length = len;
+		return storageArray.length;
+	}
+
+}
+// ====
+// compileViaYul: true
+// ----
+// set_get_length(uint256): 0 -> 0
+// set_get_length(uint256): 1 -> 1
+// set_get_length(uint256): 10 -> 10
+// set_get_length(uint256): 20 -> 20
+// set_get_length(uint256): 0 -> 0
+// set_get_length(uint256): 0xFF -> 0xFF
+// set_get_length(uint256): 0xFFFF -> 0xFFFF