From a2e3bcbd0c45a79a9709dc8a69858765ab904805 Mon Sep 17 00:00:00 2001
From: chriseth <c@ethdev.com>
Date: Thu, 30 Apr 2015 15:31:16 +0200
Subject: [PATCH] Make KnownState work with all instructions.

---
 ExpressionClasses.cpp   | 19 ++++++++++-----
 KnownState.cpp          |  7 ++++++
 SemanticInformation.cpp | 54 +++++++++++++++++++++++++++++++++++++++++
 SemanticInformation.h   |  9 +++++++
 4 files changed, 83 insertions(+), 6 deletions(-)

diff --git a/ExpressionClasses.cpp b/ExpressionClasses.cpp
index e62f75264..cfbeba7fa 100644
--- a/ExpressionClasses.cpp
+++ b/ExpressionClasses.cpp
@@ -57,12 +57,15 @@ ExpressionClasses::Id ExpressionClasses::find(
 	exp.arguments = _arguments;
 	exp.sequenceNumber = _sequenceNumber;
 
-	if (SemanticInformation::isCommutativeOperation(_item))
-		sort(exp.arguments.begin(), exp.arguments.end());
+	if (SemanticInformation::isDeterministic(_item))
+	{
+		if (SemanticInformation::isCommutativeOperation(_item))
+			sort(exp.arguments.begin(), exp.arguments.end());
 
-	auto it = m_expressions.find(exp);
-	if (it != m_expressions.end())
-		return it->id;
+		auto it = m_expressions.find(exp);
+		if (it != m_expressions.end())
+			return it->id;
+	}
 
 	if (_copyItem)
 		exp.item = storeItem(_item);
@@ -286,7 +289,11 @@ ExpressionClasses::Id ExpressionClasses::tryToSimplify(Expression const& _expr,
 {
 	static Rules rules;
 
-	if (!_expr.item || _expr.item->type() != Operation)
+	if (
+		!_expr.item ||
+		_expr.item->type() != Operation ||
+		!SemanticInformation::isDeterministic(*_expr.item)
+	)
 		return -1;
 
 	for (auto const& rule: rules.rules())
diff --git a/KnownState.cpp b/KnownState.cpp
index 02c6ee136..632777c82 100644
--- a/KnownState.cpp
+++ b/KnownState.cpp
@@ -101,6 +101,7 @@ KnownState::StoreOperation KnownState::feedItem(AssemblyItem const& _item, bool
 			vector<Id> arguments(info.args);
 			for (int i = 0; i < info.args; ++i)
 				arguments[i] = stackElement(m_stackHeight - i, _item.getLocation());
+
 			if (_item.instruction() == Instruction::SSTORE)
 				op = storeInStorage(arguments[0], arguments[1], _item.getLocation());
 			else if (_item.instruction() == Instruction::SLOAD)
@@ -121,10 +122,16 @@ KnownState::StoreOperation KnownState::feedItem(AssemblyItem const& _item, bool
 					applySha3(arguments.at(0), arguments.at(1), _item.getLocation())
 				);
 			else
+			{
+				if (SemanticInformation::invalidatesMemory(_item.instruction()))
+					resetMemory();
+				if (SemanticInformation::invalidatesStorage(_item.instruction()))
+					resetStorage();
 				setStackElement(
 					m_stackHeight + _item.deposit(),
 					m_expressionClasses->find(_item, arguments, _copyItem)
 				);
+			}
 		}
 		m_stackHeight += _item.deposit();
 	}
diff --git a/SemanticInformation.cpp b/SemanticInformation.cpp
index 83d59efc7..40c36f9e3 100644
--- a/SemanticInformation.cpp
+++ b/SemanticInformation.cpp
@@ -122,3 +122,57 @@ bool SemanticInformation::altersControlFlow(AssemblyItem const& _item)
 		return false;
 	}
 }
+
+
+bool SemanticInformation::isDeterministic(AssemblyItem const& _item)
+{
+	if (_item.type() != Operation)
+		return true;
+	assertThrow(!altersControlFlow(_item), OptimizerException, "");
+
+	switch (_item.instruction())
+	{
+	case Instruction::CALL:
+	case Instruction::CALLCODE:
+	case Instruction::CREATE:
+	case Instruction::GAS:
+	case Instruction::PC:
+	case Instruction::MSIZE: // depends on previous writes and reads, not only on content
+	case Instruction::BALANCE: // depends on previous calls
+	case Instruction::EXTCODESIZE:
+		return false;
+	default:
+		return true;
+	}
+}
+
+bool SemanticInformation::invalidatesMemory(Instruction _instruction)
+{
+	switch (_instruction)
+	{
+	case Instruction::CALLDATACOPY:
+	case Instruction::CODECOPY:
+	case Instruction::EXTCODECOPY:
+	case Instruction::MSTORE:
+	case Instruction::MSTORE8:
+	case Instruction::CALL:
+	case Instruction::CALLCODE:
+		return true;
+	default:
+		return false;
+	}
+}
+
+bool SemanticInformation::invalidatesStorage(Instruction _instruction)
+{
+	switch (_instruction)
+	{
+	case Instruction::CALL:
+	case Instruction::CALLCODE:
+	case Instruction::CREATE:
+	case Instruction::SSTORE:
+		return true;
+	default:
+		return false;
+	}
+}
diff --git a/SemanticInformation.h b/SemanticInformation.h
index 27aa6f1a4..b14ddb65a 100644
--- a/SemanticInformation.h
+++ b/SemanticInformation.h
@@ -23,6 +23,7 @@
 
 #pragma once
 
+#include <libevmcore/Instruction.h>
 
 namespace dev
 {
@@ -45,6 +46,14 @@ struct SemanticInformation
 	static bool isSwapInstruction(AssemblyItem const& _item);
 	static bool isJumpInstruction(AssemblyItem const& _item);
 	static bool altersControlFlow(AssemblyItem const& _item);
+	/// @returns false if the value put on the stack by _item depends on anything else than
+	/// the information in the current block header, memory, storage or stack.
+	/// @note should not be called for instructions that alter the control flow.
+	static bool isDeterministic(AssemblyItem const& _item);
+	/// @returns true if the given instruction modifies memory.
+	static bool invalidatesMemory(Instruction _instruction);
+	/// @returns true if the given instruction modifies storage (even indirectly).
+	static bool invalidatesStorage(Instruction _instruction);
 };
 
 }