From 1eb8d8f10b6bc321548dbe4e8dc9fee67e47996f Mon Sep 17 00:00:00 2001
From: Daniel Kirchner <daniel@ekpyron.org>
Date: Tue, 6 Oct 2020 11:30:38 +0200
Subject: [PATCH] Split StackToMemoryMover into assignment+declaration and
 identifier movers.

---
 libyul/optimiser/StackToMemoryMover.cpp | 39 +++++++++++---------
 libyul/optimiser/StackToMemoryMover.h   | 48 +++++++++++++++++--------
 2 files changed, 55 insertions(+), 32 deletions(-)

diff --git a/libyul/optimiser/StackToMemoryMover.cpp b/libyul/optimiser/StackToMemoryMover.cpp
index db9bbef21..722c7a5b6 100644
--- a/libyul/optimiser/StackToMemoryMover.cpp
+++ b/libyul/optimiser/StackToMemoryMover.cpp
@@ -58,28 +58,22 @@ void StackToMemoryMover::run(
 	uint64_t _numRequiredSlots,
 	Block& _block
 )
-{
-	VariableMemoryOffsetTracker memoryOffsetTracker(_reservedMemory, _memorySlots, _numRequiredSlots);
-	StackToMemoryMover stackToMemoryMover(_context, memoryOffsetTracker);
-	stackToMemoryMover(_block);
-}
-
-StackToMemoryMover::StackToMemoryMover(
-	OptimiserStepContext& _context,
-	VariableMemoryOffsetTracker const& _memoryOffsetTracker
-):
-m_context(_context),
-m_memoryOffsetTracker(_memoryOffsetTracker),
-m_nameDispenser(_context.dispenser)
 {
 	auto const* evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
 	yulAssert(
 		evmDialect && evmDialect->providesObjectAccess(),
 		"StackToMemoryMover can only be run on objects using the EVMDialect with object access."
 	);
+	VariableMemoryOffsetTracker memoryOffsetTracker(_reservedMemory, _memorySlots, _numRequiredSlots);
+
+	VariableDeclarationAndAssignmentMover declarationAndAssignmentMover(_context, memoryOffsetTracker);
+	declarationAndAssignmentMover(_block);
+
+	IdentifierMover identifierMover(_context, memoryOffsetTracker);
+	identifierMover(_block);
 }
 
-void StackToMemoryMover::operator()(FunctionDefinition& _functionDefinition)
+void StackToMemoryMover::VariableDeclarationAndAssignmentMover::operator()(FunctionDefinition& _functionDefinition)
 {
 	for (TypedName const& param: _functionDefinition.parameters + _functionDefinition.returnVariables)
 		if (m_memoryOffsetTracker(param.name))
@@ -90,7 +84,18 @@ void StackToMemoryMover::operator()(FunctionDefinition& _functionDefinition)
 	ASTModifier::operator()(_functionDefinition);
 }
 
-void StackToMemoryMover::operator()(Block& _block)
+void StackToMemoryMover::IdentifierMover::operator()(FunctionDefinition& _functionDefinition)
+{
+	for (TypedName const& param: _functionDefinition.parameters + _functionDefinition.returnVariables)
+		if (m_memoryOffsetTracker(param.name))
+		{
+			// TODO: we cannot handle function parameters yet.
+			return;
+		}
+	ASTModifier::operator()(_functionDefinition);
+}
+
+void StackToMemoryMover::VariableDeclarationAndAssignmentMover::operator()(Block& _block)
 {
 	using OptionalStatements = std::optional<vector<Statement>>;
 	auto containsVariableNeedingEscalation = [&](auto const& _variables) {
@@ -120,7 +125,7 @@ void StackToMemoryMover::operator()(Block& _block)
 		vector<Statement> variableAssignments;
 		for (auto& var: _variables)
 		{
-			YulString tempVarName = m_nameDispenser.newName(var.name);
+			YulString tempVarName = m_context.dispenser.newName(var.name);
 			tempDecl.variables.emplace_back(TypedName{var.location, tempVarName, {}});
 
 			if (optional<YulString> offset = m_memoryOffsetTracker(var.name))
@@ -184,7 +189,7 @@ void StackToMemoryMover::operator()(Block& _block)
 		});
 }
 
-void StackToMemoryMover::visit(Expression& _expression)
+void StackToMemoryMover::IdentifierMover::visit(Expression& _expression)
 {
 	if (Identifier* identifier = std::get_if<Identifier>(&_expression))
 		if (optional<YulString> offset = m_memoryOffsetTracker(identifier->name))
diff --git a/libyul/optimiser/StackToMemoryMover.h b/libyul/optimiser/StackToMemoryMover.h
index 5cbc5a5a0..c26130b8d 100644
--- a/libyul/optimiser/StackToMemoryMover.h
+++ b/libyul/optimiser/StackToMemoryMover.h
@@ -75,7 +75,7 @@ namespace solidity::yul
  *
  * Prerequisite: Disambiguator, ForLoopInitRewriter, FunctionHoister.
  */
-class StackToMemoryMover: ASTModifier
+class StackToMemoryMover
 {
 public:
 	/**
@@ -94,11 +94,6 @@ public:
 		uint64_t _numRequiredSlots,
 		Block& _block
 	);
-	using ASTModifier::operator();
-
-	void operator()(FunctionDefinition& _functionDefinition) override;
-	void operator()(Block& _block) override;
-	void visit(Expression& _expression) override;
 private:
 	class VariableMemoryOffsetTracker
 	{
@@ -118,15 +113,38 @@ private:
 		std::map<YulString, uint64_t> const& m_memorySlots;
 		uint64_t m_numRequiredSlots = 0;
 	};
-
-	StackToMemoryMover(
-		OptimiserStepContext& _context,
-		VariableMemoryOffsetTracker const& _memoryOffsetTracker
-	);
-
-	OptimiserStepContext& m_context;
-	VariableMemoryOffsetTracker const& m_memoryOffsetTracker;
-	NameDispenser& m_nameDispenser;
+	class VariableDeclarationAndAssignmentMover: ASTModifier
+	{
+	public:
+		VariableDeclarationAndAssignmentMover(
+			OptimiserStepContext& _context,
+			VariableMemoryOffsetTracker const& _memoryOffsetTracker
+		): m_context(_context), m_memoryOffsetTracker(_memoryOffsetTracker)
+		{
+		}
+		using ASTModifier::operator();
+		void operator()(FunctionDefinition& _functionDefinition) override;
+		void operator()(Block& _block) override;
+	private:
+		OptimiserStepContext& m_context;
+		VariableMemoryOffsetTracker const& m_memoryOffsetTracker;
+	};
+	class IdentifierMover: ASTModifier
+	{
+	public:
+		IdentifierMover(
+			OptimiserStepContext& _context,
+			VariableMemoryOffsetTracker const& _memoryOffsetTracker
+		): m_context(_context), m_memoryOffsetTracker(_memoryOffsetTracker)
+		{
+		}
+		using ASTModifier::operator();
+		void operator()(FunctionDefinition& _functionDefinition) override;
+		void visit(Expression& _expression) override;
+	private:
+		OptimiserStepContext& m_context;
+		VariableMemoryOffsetTracker const& m_memoryOffsetTracker;
+	};
 };
 
 }
\ No newline at end of file