Merge pull request #7833 from ethereum/combineValueAndLoopDepth

Combine value and loop depth

libyul/optimiser/CommonSubexpressionEliminator.cpp

@@ -79,10 +79,10 @@ void CommonSubexpressionEliminator::visit(Expression& _e)
 		YulString name = identifier.name;
 		if (m_value.count(name))
 		{
-			assertThrow(m_value.at(name), OptimizerException, "");
+			assertThrow(m_value.at(name).value, OptimizerException, "");
-			if (holds_alternative<Identifier>(*m_value.at(name)))
+			if (holds_alternative<Identifier>(*m_value.at(name).value))
 			{
-				YulString value = std::get<Identifier>(*m_value.at(name)).name;
+				YulString value = std::get<Identifier>(*m_value.at(name).value).name;
 				assertThrow(inScope(value), OptimizerException, "");
 				_e = Identifier{locationOf(_e), value};
 			}
@@ -91,13 +91,13 @@ void CommonSubexpressionEliminator::visit(Expression& _e)
 	else
 	{
 		// TODO this search is rather inefficient.
-		for (auto const& var: m_value)
+		for (auto const& [variable, value]: m_value)
 		{
-			assertThrow(var.second, OptimizerException, "");
+			assertThrow(value.value, OptimizerException, "");
-			assertThrow(inScope(var.first), OptimizerException, "");
+			assertThrow(inScope(variable), OptimizerException, "");
-			if (SyntacticallyEqual{}(_e, *var.second))
+			if (SyntacticallyEqual{}(_e, *value.value))
 			{
-				_e = Identifier{locationOf(_e), var.first};
+				_e = Identifier{locationOf(_e), variable};
 				break;
 			}
 		}

libyul/optimiser/DataFlowAnalyzer.cpp

@@ -144,14 +144,12 @@ void DataFlowAnalyzer::operator()(FunctionDefinition& _fun)
 {
 	// Save all information. We might rather reinstantiate this class,
 	// but this could be difficult if it is subclassed.
-	map<YulString, Expression const*> value;
+	map<YulString, AssignedValue> value;
-	map<YulString, size_t> variableLoopDepth;
 	size_t loopDepth{0};
 	InvertibleRelation<YulString> references;
 	InvertibleMap<YulString, YulString> storage;
 	InvertibleMap<YulString, YulString> memory;
 	swap(m_value, value);
-	swap(m_variableLoopDepth, variableLoopDepth);
 	swap(m_loopDepth, loopDepth);
 	swap(m_references, references);
 	swap(m_storage, storage);
@@ -173,7 +171,6 @@ void DataFlowAnalyzer::operator()(FunctionDefinition& _fun)
 
 	popScope();
 	swap(m_value, value);
-	swap(m_variableLoopDepth, variableLoopDepth);
 	swap(m_loopDepth, loopDepth);
 	swap(m_references, references);
 	swap(m_storage, storage);
@@ -306,18 +303,14 @@ void DataFlowAnalyzer::clearValues(set<YulString> _variables)
 
 	// Clear the value and update the reference relation.
 	for (auto const& name: _variables)
-	{
 		m_value.erase(name);
-		m_variableLoopDepth.erase(name);
-	}
 	for (auto const& name: _variables)
 		m_references.eraseKey(name);
 }
 
 void DataFlowAnalyzer::assignValue(YulString _variable, Expression const* _value)
 {
-	m_value[_variable] = _value;
+	m_value[_variable] = {_value, m_loopDepth};
-	m_variableLoopDepth[_variable] = m_loopDepth;
 }
 
 void DataFlowAnalyzer::clearKnowledgeIfInvalidated(Block const& _block)

libyul/optimiser/DataFlowAnalyzer.h

@@ -41,6 +41,14 @@ namespace solidity::yul
 struct Dialect;
 struct SideEffects;
 
+/// Value assigned to a variable.
+struct AssignedValue
+{
+	Expression const* value{nullptr};
+	/// Loop nesting depth of the definition of the variable.
+	size_t loopDepth{0};
+};
+
 /**
  * Base class to perform data flow analysis during AST walks.
  * Tracks assignments and is used as base class for both Rematerialiser and
@@ -145,9 +153,7 @@ protected:
 	std::map<YulString, SideEffects> m_functionSideEffects;
 
 	/// Current values of variables, always movable.
-	std::map<YulString, Expression const*> m_value;
+	std::map<YulString, AssignedValue> m_value;
-	/// The loop nesting depth of the definition of variables (those used in m_value).
-	std::map<YulString, size_t> m_variableLoopDepth;
 	/// m_references.forward[a].contains(b) <=> the current expression assigned to a references b
 	/// m_references.backward[b].contains(a) <=> the current expression assigned to a references b
 	InvertibleRelation<YulString> m_references;

libyul/optimiser/KnowledgeBase.cpp

@@ -23,6 +23,7 @@
 #include <libyul/AsmData.h>
 #include <libyul/Utilities.h>
 #include <libyul/optimiser/SimplificationRules.h>
+#include <libyul/optimiser/DataFlowAnalyzer.h>
 #include <libyul/optimiser/Semantics.h>
 
 #include <libsolutil/CommonData.h>

libyul/optimiser/KnowledgeBase.h

@@ -28,6 +28,7 @@ namespace solidity::yul
 {
 
 struct Dialect;
+struct AssignedValue;
 
 /**
  * Class that can answer questions about values of variables and their relations.
@@ -37,7 +38,7 @@ struct Dialect;
 class KnowledgeBase
 {
 public:
-	KnowledgeBase(Dialect const& _dialect, std::map<YulString, Expression const*> const& _variableValues):
+	KnowledgeBase(Dialect const& _dialect, std::map<YulString, AssignedValue> const& _variableValues):
 		m_dialect(_dialect),
 		m_variableValues(_variableValues)
 	{}
@@ -50,7 +51,7 @@ private:
 	Expression simplify(Expression _expression);
 
 	Dialect const& m_dialect;
-	std::map<YulString, Expression const*> const& m_variableValues;
+	std::map<YulString, AssignedValue> const& m_variableValues;
 	size_t m_recursionCounter = 0;
 };
 

libyul/optimiser/Rematerialiser.cpp

@@ -74,12 +74,12 @@ void Rematerialiser::visit(Expression& _e)
 		YulString name = identifier.name;
 		if (m_value.count(name))
 		{
-			assertThrow(m_value.at(name), OptimizerException, "");
+			assertThrow(m_value.at(name).value, OptimizerException, "");
-			auto const& value = *m_value.at(name);
+			AssignedValue const& value = m_value.at(name);
 			size_t refs = m_referenceCounts[name];
-			size_t cost = CodeCost::codeCost(m_dialect, value);
+			size_t cost = CodeCost::codeCost(m_dialect, *value.value);
 			if (
-				(refs <= 1 && m_variableLoopDepth.at(name) == m_loopDepth) ||
+				(refs <= 1 && value.loopDepth == m_loopDepth) ||
 				cost == 0 ||
 				(refs <= 5 && cost <= 1 && m_loopDepth == 0) ||
 				m_varsToAlwaysRematerialize.count(name)
@@ -90,9 +90,9 @@ void Rematerialiser::visit(Expression& _e)
 					assertThrow(inScope(ref), OptimizerException, "");
 				// update reference counts
 				m_referenceCounts[name]--;
-				for (auto const& ref: ReferencesCounter::countReferences(value))
+				for (auto const& ref: ReferencesCounter::countReferences(*value.value))
 					m_referenceCounts[ref.first] += ref.second;
-				_e = (ASTCopier{}).translate(value);
+				_e = (ASTCopier{}).translate(*value.value);
 			}
 		}
 	}
@@ -107,7 +107,7 @@ void LiteralRematerialiser::visit(Expression& _e)
 		YulString name = identifier.name;
 		if (m_value.count(name))
 		{
-			Expression const* value = m_value.at(name);
+			Expression const* value = m_value.at(name).value;
 			assertThrow(value, OptimizerException, "");
 			if (holds_alternative<Literal>(*value))
 				_e = *value;

libyul/optimiser/SimplificationRules.cpp

@@ -23,6 +23,7 @@
 #include <libyul/optimiser/ASTCopier.h>
 #include <libyul/optimiser/Semantics.h>
 #include <libyul/optimiser/SyntacticalEquality.h>
+#include <libyul/optimiser/DataFlowAnalyzer.h>
 #include <libyul/backends/evm/EVMDialect.h>
 #include <libyul/AsmData.h>
 #include <libyul/Utilities.h>
@@ -38,7 +39,7 @@ using namespace solidity::yul;
 SimplificationRule<yul::Pattern> const* SimplificationRules::findFirstMatch(
 	Expression const& _expr,
 	Dialect const& _dialect,
-	map<YulString, Expression const*> const& _ssaValues
+	map<YulString, AssignedValue> const& _ssaValues
 )
 {
 	auto instruction = instructionAndArguments(_dialect, _expr);
@@ -126,7 +127,7 @@ void Pattern::setMatchGroup(unsigned _group, map<unsigned, Expression const*>& _
 bool Pattern::matches(
 	Expression const& _expr,
 	Dialect const& _dialect,
-	map<YulString, Expression const*> const& _ssaValues
+	map<YulString, AssignedValue> const& _ssaValues
 ) const
 {
 	Expression const* expr = &_expr;
@@ -137,7 +138,7 @@ bool Pattern::matches(
 	{
 		YulString varName = std::get<Identifier>(_expr).name;
 		if (_ssaValues.count(varName))
-			if (Expression const* new_expr = _ssaValues.at(varName))
+			if (Expression const* new_expr = _ssaValues.at(varName).value)
 				expr = new_expr;
 	}
 	assertThrow(expr, OptimizerException, "");

libyul/optimiser/SimplificationRules.h

@@ -36,6 +36,7 @@
 namespace solidity::yul
 {
 struct Dialect;
+struct AssignedValue;
 class Pattern;
 
 /**
@@ -52,7 +53,7 @@ public:
 	static evmasm::SimplificationRule<Pattern> const* findFirstMatch(
 		Expression const& _expr,
 		Dialect const& _dialect,
-		std::map<YulString, Expression const*> const& _ssaValues
+		std::map<YulString, AssignedValue> const& _ssaValues
 	);
 
 	/// Checks whether the rulelist is non-empty. This is usually enforced
@@ -109,7 +110,7 @@ public:
 	bool matches(
 		Expression const& _expr,
 		Dialect const& _dialect,
-		std::map<YulString, Expression const*> const& _ssaValues
+		std::map<YulString, AssignedValue> const& _ssaValues
 	) const;
 
 	std::vector<Pattern> arguments() const { return m_arguments; }

libyul/optimiser/StackCompressor.cpp

@@ -70,7 +70,7 @@ public:
 		{
 			YulString varName = _varDecl.variables.front().name;
 			if (m_value.count(varName))
-				m_expressionCodeCost[varName] = CodeCost::codeCost(m_dialect, *m_value[varName]);
+				m_expressionCodeCost[varName] = CodeCost::codeCost(m_dialect, *m_value[varName].value);
 		}
 	}