codegen: add an option to CovertType so that it can truncate sign bits

3 files changed, 22 insertions, 10 deletions

diff --git a/libsolidity/codegen/CompilerUtils.cpp b/libsolidity/codegen/CompilerUtils.cpp
index fe2b9c7e..21dd2840 100644
--- a/libsolidity/codegen/CompilerUtils.cpp
+++ b/libsolidity/codegen/CompilerUtils.cpp
@@ -358,7 +358,7 @@ void CompilerUtils::pushCombinedFunctionEntryLabel(Declaration const& _function)
 			Instruction::OR;
 }
 
-void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetType, bool _cleanupNeeded)
+void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetType, bool _cleanupNeeded, bool _chopSignBits)
 {
 	// For a type extension, we need to remove all higher-order bits that we might have ignored in
 	// previous operations.
@@ -370,6 +370,12 @@ void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetTyp
 	Type::Category targetTypeCategory = _targetType.category();
 
 	bool enumOverflowCheckPending = (targetTypeCategory == Type::Category::Enum || stackTypeCategory == Type::Category::Enum);
+	bool chopSignBitsPending = _chopSignBits && targetTypeCategory == Type::Category::Integer;
+	if (chopSignBitsPending)
+	{
+		const IntegerType& targetIntegerType = dynamic_cast<const IntegerType &>(_targetType);
+		chopSignBitsPending = targetIntegerType.isSigned();
+	}
 
 	switch (stackTypeCategory)
 	{
@@ -482,6 +488,17 @@ void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetTyp
 					cleanHigherOrderBits(typeOnStack);
 				else if (_cleanupNeeded)
 					cleanHigherOrderBits(targetType);
+				if (chopSignBitsPending)
+				{
+					if (typeOnStack.numBits() < 256)
+						m_context
+							<< (u256(1) << (256 - typeOnStack.numBits()))
+							<< Instruction::SWAP1
+							<< Instruction::DUP2
+							<< Instruction::MUL
+							<< Instruction::DIV;
+					chopSignBitsPending = false;
+				}
 			}
 		}
 		break;
@@ -728,6 +745,7 @@ void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetTyp
 	}
 
 	solAssert(!enumOverflowCheckPending, "enum overflow checking missing.");
+	solAssert(!chopSignBitsPending, "forgot to chop the sign bits.");
 }
 
 void CompilerUtils::pushZeroValue(Type const& _type)
diff --git a/libsolidity/codegen/CompilerUtils.h b/libsolidity/codegen/CompilerUtils.h
index ff87124f..977e96d9 100644
--- a/libsolidity/codegen/CompilerUtils.h
+++ b/libsolidity/codegen/CompilerUtils.h
@@ -130,7 +130,7 @@ public:
 	/// if a reference type is converted from calldata or storage to memory.
 	/// If @a _cleanupNeeded, high order bits cleanup is also done if no type conversion would be
 	/// necessary.
-	void convertType(Type const& _typeOnStack, Type const& _targetType, bool _cleanupNeeded = false);
+	void convertType(Type const& _typeOnStack, Type const& _targetType, bool _cleanupNeeded = false, bool _chopSignBits = false);
 
 	/// Creates a zero-value for the given type and puts it onto the stack. This might allocate
 	/// memory for memory references.
diff --git a/libsolidity/codegen/LValue.cpp b/libsolidity/codegen/LValue.cpp
index 78854588..df74e836 100644
--- a/libsolidity/codegen/LValue.cpp
+++ b/libsolidity/codegen/LValue.cpp
@@ -234,7 +234,7 @@ void StorageItem::storeValue(Type const& _sourceType, SourceLocation const& _loc
 
 			m_context << Instruction::SWAP1;
 			utils.convertType(_sourceType, _sourceType, true);
-			utils.convertType(*m_dataType, *m_dataType, true);
+			utils.convertType(*m_dataType, *m_dataType, true, true);
 			m_context << Instruction::SWAP1;
 
 			m_context << Instruction::SSTORE;
@@ -280,13 +280,7 @@ void StorageItem::storeValue(Type const& _sourceType, SourceLocation const& _loc
 			{
 				solAssert(m_dataType->sizeOnStack() == 1, "Invalid stack size for opaque type.");
 				// remove the higher order bits
-				utils.convertType(*m_dataType, *m_dataType, true);
-				m_context
-					<< (u256(1) << (8 * (32 - m_dataType->storageBytes())))
-					<< Instruction::SWAP1
-					<< Instruction::DUP2
-					<< Instruction::MUL
-					<< Instruction::DIV;
+				utils.convertType(*m_dataType, *m_dataType, true, true);
 			}
 			m_context  << Instruction::MUL << Instruction::OR;
 			// stack: value storage_ref updated_value