Reverse the order of the memory offsets assigned to variables.

libyul/optimiser/StackLimitEvader.cpp

@@ -132,7 +132,7 @@ void StackLimitEvader::run(
 	MemoryOffsetAllocator memoryOffsetAllocator{_unreachableVariables, callGraph.functionCalls};
 	uint64_t requiredSlots = memoryOffsetAllocator.run();
 
-	StackToMemoryMover::run(_context, reservedMemory, memoryOffsetAllocator.slotAllocations, *_object.code);
+	StackToMemoryMover::run(_context, reservedMemory, memoryOffsetAllocator.slotAllocations, requiredSlots, *_object.code);
 
 	yulAssert(requiredSlots < std::numeric_limits<uint64_t>::max() / 32, "");
 	reservedMemory += 32 * requiredSlots;

libyul/optimiser/StackToMemoryMover.cpp

@@ -52,18 +52,24 @@ void StackToMemoryMover::run(
 	OptimiserStepContext& _context,
 	u256 _reservedMemory,
 	map<YulString, map<YulString, uint64_t>> const& _memorySlots,
+	uint64_t _numRequiredSlots,
 	Block& _block
 )
 {
-	StackToMemoryMover stackToMemoryMover(_context, _reservedMemory, _memorySlots);
+	StackToMemoryMover stackToMemoryMover(_context, _reservedMemory, _memorySlots, _numRequiredSlots);
 	stackToMemoryMover(_block);
 }
 
 StackToMemoryMover::StackToMemoryMover(
 	OptimiserStepContext& _context,
 	u256 _reservedMemory,
-	map<YulString, map<YulString, uint64_t>> const& _memorySlots
-): m_reservedMemory(std::move(_reservedMemory)), m_memorySlots(_memorySlots), m_nameDispenser(_context.dispenser)
+	map<YulString, map<YulString, uint64_t>> const& _memorySlots,
+	uint64_t _numRequiredSlots
+):
+m_reservedMemory(std::move(_reservedMemory)),
+m_memorySlots(_memorySlots),
+m_numRequiredSlots(_numRequiredSlots),
+m_nameDispenser(_context.dispenser)
 {
 	auto const* evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
 	yulAssert(
@@ -210,6 +216,8 @@ void StackToMemoryMover::visit(Expression& _expression)
 YulString StackToMemoryMover::memoryOffset(YulString _variable)
 {
 	yulAssert(m_currentFunctionMemorySlots, "");
-	return YulString{util::toCompactHexWithPrefix(m_reservedMemory + 32 * m_currentFunctionMemorySlots->at(_variable))};
+	uint64_t slot = m_currentFunctionMemorySlots->at(_variable);
+	yulAssert(slot < m_numRequiredSlots, "");
+	return YulString{util::toCompactHexWithPrefix(m_reservedMemory + 32 * (m_numRequiredSlots - slot - 1))};
 }
 

libyul/optimiser/StackToMemoryMover.h

@@ -82,13 +82,16 @@ public:
 	 * Runs the stack to memory mover.
 	 * @param _reservedMemory Is the amount of previously reserved memory,
 	 *                        i.e. the lowest memory offset to which variables can be moved.
-	 * @param _memorySlots A map from variables to a slot in memory. The offset to which a variables will be moved
-	 *                       is given by _reservedMemory plus 32 times its entry in @a _memorySlots.
+	 * @param _memorySlots A map from variables to a slot in memory. Based on the slot a unique offset in the memory range
+	 *                     between _reservedMemory and _reservedMemory + 32 * _numRequiredSlots is calculated for each
+	 *                     variable.
+	 * @param _numRequiredSlots The number of slots required in total. The maximum value that may occur in @a _memorySlots.
 	 */
 	static void run(
 		OptimiserStepContext& _context,
 		u256 _reservedMemory,
 		std::map<YulString, std::map<YulString, uint64_t>> const& _memorySlots,
+		uint64_t _numRequiredSlots,
 		Block& _block
 	);
 	using ASTModifier::operator();
@@ -100,13 +103,15 @@ private:
 	StackToMemoryMover(
 		OptimiserStepContext& _context,
 		u256 _reservedMemory,
-		std::map<YulString, std::map<YulString, uint64_t>> const& _memorySlots
+		std::map<YulString, std::map<YulString, uint64_t>> const& _memorySlots,
+		uint64_t _numRequiredSlots
 	);
 
 	/// @returns a YulString containing the memory offset to be assigned to @a _variable as number literal.
 	YulString memoryOffset(YulString _variable);
 	u256 m_reservedMemory;
 	std::map<YulString, std::map<YulString, uint64_t>> const& m_memorySlots;
+	uint64_t m_numRequiredSlots = 0;
 	NameDispenser& m_nameDispenser;
 	std::map<YulString, uint64_t> const* m_currentFunctionMemorySlots = nullptr;
 };