Merge pull request #6848 from ethereum/invertibleRelation

Implement references using InvertibleRelation as data structure.

libyul/optimiser/DataFlowAnalyzer.cpp

@@ -88,11 +88,9 @@ 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, set<YulString>> references;
-	map<YulString, set<YulString>> referencedBy;
+	InvertibleRelation<YulString> references;
 	m_value.swap(value);
-	m_references.swap(references);
-	m_referencedBy.swap(referencedBy);
+	swap(m_references, references);
 	pushScope(true);
 
 	for (auto const& parameter: _fun.parameters)
@@ -106,8 +104,7 @@ void DataFlowAnalyzer::operator()(FunctionDefinition& _fun)
 
 	popScope();
 	m_value.swap(value);
-	m_references.swap(references);
-	m_referencedBy.swap(referencedBy);
+	swap(m_references, references);
 }
 
 void DataFlowAnalyzer::operator()(ForLoop& _for)
@@ -162,11 +159,7 @@ void DataFlowAnalyzer::handleAssignment(set<YulString> const& _variables, Expres
 
 	auto const& referencedVariables = movableChecker.referencedVariables();
 	for (auto const& name: _variables)
-	{
-		m_references[name] = referencedVariables;
-		for (auto const& ref: referencedVariables)
-			m_referencedBy[ref].emplace(name);
-	}
+		m_references.set(name, referencedVariables);
 }
 
 void DataFlowAnalyzer::pushScope(bool _functionScope)
@@ -197,18 +190,14 @@ void DataFlowAnalyzer::clearValues(set<YulString> _variables)
 
 	// Clear variables that reference variables to be cleared.
 	for (auto const& name: _variables)
-		for (auto const& ref: m_referencedBy[name])
+		for (auto const& ref: m_references.backward[name])
 			_variables.emplace(ref);
 
 	// Clear the value and update the reference relation.
 	for (auto const& name: _variables)
 		m_value.erase(name);
 	for (auto const& name: _variables)
-	{
-		for (auto const& ref: m_references[name])
-			m_referencedBy[ref].erase(name);
-		m_references[name].clear();
-	}
+		m_references.eraseKey(name);
 }
 
 bool DataFlowAnalyzer::inScope(YulString _variableName) const

libyul/optimiser/DataFlowAnalyzer.h

@@ -26,6 +26,8 @@
 #include <libyul/YulString.h>
 #include <libyul/AsmData.h>
 
+#include <libdevcore/InvertibleMap.h>
+
 #include <map>
 #include <set>
 
@@ -75,10 +77,9 @@ protected:
 
 	/// Current values of variables, always movable.
 	std::map<YulString, Expression const*> m_value;
-	/// m_references[a].contains(b) <=> the current expression assigned to a references b
-	std::map<YulString, std::set<YulString>> m_references;
-	/// m_referencedBy[b].contains(a) <=> the current expression assigned to a references b
-	std::map<YulString, std::set<YulString>> m_referencedBy;
+	/// 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;
 
 	struct Scope
 	{

libyul/optimiser/Rematerialiser.cpp

@@ -81,7 +81,7 @@ void Rematerialiser::visit(Expression& _e)
 			if (refs <= 1 || cost == 0 || (refs <= 5 && cost <= 1) || m_varsToAlwaysRematerialize.count(name))
 			{
 				assertThrow(m_referenceCounts[name] > 0, OptimizerException, "");
-				for (auto const& ref: m_references[name])
+				for (auto const& ref: m_references.forward[name])
 					assertThrow(inScope(ref), OptimizerException, "");
 				// update reference counts
 				m_referenceCounts[name]--;

libyul/optimiser/StackCompressor.cpp

@@ -57,7 +57,7 @@ public:
 		for (auto const& codeCost: m_expressionCodeCost)
 		{
 			size_t numRef = m_numReferences[codeCost.first];
-			cand.emplace(make_tuple(codeCost.second * numRef, codeCost.first, m_references[codeCost.first]));
+			cand.emplace(make_tuple(codeCost.second * numRef, codeCost.first, m_references.forward[codeCost.first]));
 		}
 		return cand;
 	}