From aa23ebc8e6df52c87060d3c824a549ff67f8efdf Mon Sep 17 00:00:00 2001
From: Djordje Mijovic <djordje.mijovic@gmail.com>
Date: Fri, 18 Sep 2020 15:10:23 +0200
Subject: [PATCH] [Sol->Yul] Implementing array resizing for packed array
 types.

---
 libsolidity/codegen/YulUtilFunctions.cpp | 34 +++++++++++++++++++++---
 libsolidity/codegen/YulUtilFunctions.h   |  5 ++++
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/libsolidity/codegen/YulUtilFunctions.cpp b/libsolidity/codegen/YulUtilFunctions.cpp
index 4ac32a1fa..f976f8066 100644
--- a/libsolidity/codegen/YulUtilFunctions.cpp
+++ b/libsolidity/codegen/YulUtilFunctions.cpp
@@ -873,6 +873,12 @@ std::string YulUtilFunctions::resizeDynamicArrayFunction(ArrayType const& _type)
 					let arrayDataStart := <dataPosition>(array)
 					let deleteStart := add(arrayDataStart, newSlotCount)
 					let deleteEnd := add(arrayDataStart, oldSlotCount)
+					<?packed>
+						// if we are dealing with packed array and offset is greater than zero
+						// we have  to partially clear last slot that is still used, so decreasing start by one
+						let offset := mul(mod(newLen, <itemsPerSlot>), <storageBytes>)
+						if gt(offset, 0) { <partialClearStorageSlot>(sub(deleteStart, 1), offset) }
+					</packed>
 					<clearStorageRange>(deleteStart, deleteEnd)
 				}
 			})")
@@ -883,6 +889,10 @@ std::string YulUtilFunctions::resizeDynamicArrayFunction(ArrayType const& _type)
 			("dataPosition", arrayDataAreaFunction(_type))
 			("clearStorageRange", clearStorageRangeFunction(*_type.baseType()))
 			("maxArrayLength", (u256(1) << 64).str())
+			("packed", _type.baseType()->storageBytes() <= 16)
+			("itemsPerSlot", to_string(32 / _type.baseType()->storageBytes()))
+			("storageBytes", to_string(_type.baseType()->storageBytes()))
+			("partialClearStorageSlot", partialClearStorageSlotFunction())
 			.render();
 	});
 }
@@ -1060,11 +1070,29 @@ string YulUtilFunctions::storageArrayPushZeroFunction(ArrayType const& _type)
 	});
 }
 
+string YulUtilFunctions::partialClearStorageSlotFunction()
+{
+	string functionName = "partial_clear_storage_slot";
+	return m_functionCollector.createFunction(functionName, [&]() {
+		return Whiskers(R"(
+		function <functionName>(slot, offset) {
+			let mask := <shr>(mul(8, sub(32, offset)), <ones>)
+			sstore(slot, and(mask, sload(slot)))
+		}
+		)")
+		("functionName", functionName)
+		("ones", formatNumber((bigint(1) << 256) - 1))
+		("shr", shiftRightFunctionDynamic())
+		.render();
+	});
+}
+
 string YulUtilFunctions::clearStorageRangeFunction(Type const& _type)
 {
-	string functionName = "clear_storage_range_" + _type.identifier();
+	if (_type.storageBytes() < 32)
+		solAssert(_type.isValueType(), "");
 
-	solAssert(_type.storageBytes() >= 32, "Expected smaller value for storage bytes");
+	string functionName = "clear_storage_range_" + _type.identifier();
 
 	return m_functionCollector.createFunction(functionName, [&]() {
 		return Whiskers(R"(
@@ -1076,7 +1104,7 @@ string YulUtilFunctions::clearStorageRangeFunction(Type const& _type)
 			}
 		)")
 		("functionName", functionName)
-		("setToZero", storageSetToZeroFunction(_type))
+		("setToZero", storageSetToZeroFunction(_type.storageBytes() < 32 ? *TypeProvider::uint256() : _type))
 		("increment", _type.storageSize().str())
 		.render();
 	});
diff --git a/libsolidity/codegen/YulUtilFunctions.h b/libsolidity/codegen/YulUtilFunctions.h
index 5437114f7..351c857d4 100644
--- a/libsolidity/codegen/YulUtilFunctions.h
+++ b/libsolidity/codegen/YulUtilFunctions.h
@@ -422,6 +422,11 @@ private:
 	/// @returns a function that reads a reference type from storage to memory (performing a deep copy).
 	std::string readFromStorageReferenceType(Type const& _type);
 
+	/// @returns the name of a function that will clear given storage slot
+	/// starting with given offset until the end of the slot
+	/// signature: (slot, offset)
+	std::string partialClearStorageSlotFunction();
+
 	langutil::EVMVersion m_evmVersion;
 	RevertStrings m_revertStrings;
 	MultiUseYulFunctionCollector& m_functionCollector;