Use stack optimizations.

Changelog.md

@@ -4,6 +4,7 @@ Language Features:
 
 
 Compiler Features:
+ * Yul Optimizer: Enable stack allocation optimization by default if yul optimizer is active (disable in yulDetails).
 
 
 Bugfixes:

docs/using-the-compiler.rst

@@ -216,8 +216,12 @@ Input Description
             // It can only be activated through the details here.
             // This feature is still considered experimental.
             "yul": false,
-            // Future tuning options, currently unused.
-            "yulDetails": {}
+            // Tuning options for the Yul optimizer.
+            "yulDetails": {
+              // Improve allocation of stack slots for variables, can free up stack slots early.
+              // Activated by default if the Yul optimizer is activated.
+              "stackAllocation": true
+            }
           }
         },
         "evmVersion": "byzantium", // Version of the EVM to compile for. Affects type checking and code generation. Can be homestead, tangerineWhistle, spuriousDragon, byzantium, constantinople or petersburg

libsolidity/codegen/CompilerContext.cpp

@@ -331,7 +331,7 @@ void CompilerContext::appendInlineAssembly(
 	vector<string> const& _localVariables,
 	set<string> const& _externallyUsedFunctions,
 	bool _system,
-	bool _optimise
+	OptimiserSettings const& _optimiserSettings
 )
 {
 	int startStackHeight = stackHeight();
@@ -422,7 +422,7 @@ void CompilerContext::appendInlineAssembly(
 
 	// Several optimizer steps cannot handle externally supplied stack variables,
 	// so we essentially only optimize the ABI functions.
-	if (_optimise && _localVariables.empty())
+	if (_optimiserSettings.runYulOptimiser && _localVariables.empty())
 	{
 		yul::OptimiserSuite::run(
 			yul::EVMDialect::strictAssemblyForEVM(m_evmVersion),
@@ -445,7 +445,15 @@ void CompilerContext::appendInlineAssembly(
 		reportError("Failed to analyze inline assembly block.");
 
 	solAssert(errorReporter.errors().empty(), "Failed to analyze inline assembly block.");
-	yul::CodeGenerator::assemble(*parserResult, analysisInfo, *m_asm, m_evmVersion, identifierAccess, _system, _optimise);
+	yul::CodeGenerator::assemble(
+		*parserResult,
+		analysisInfo,
+		*m_asm,
+		m_evmVersion,
+		identifierAccess,
+		_system,
+		_optimiserSettings.optimizeStackAllocation
+	);
 
 	// Reset the source location to the one of the node (instead of the CODEGEN source location)
 	updateSourceLocation();

libsolidity/codegen/CompilerContext.h

@@ -217,7 +217,7 @@ public:
 		std::vector<std::string> const& _localVariables = std::vector<std::string>(),
 		std::set<std::string> const& _externallyUsedFunctions = std::set<std::string>(),
 		bool _system = false,
-		bool _optimise = false
+		OptimiserSettings const& _optimiserSettings = OptimiserSettings::none()
 	);
 
 	/// Appends arbitrary data to the end of the bytecode.

libsolidity/codegen/ContractCompiler.cpp

@@ -720,7 +720,9 @@ bool ContractCompiler::visit(InlineAssembly const& _inlineAssembly)
 		*_inlineAssembly.annotation().analysisInfo,
 		*m_context.assemblyPtr(),
 		m_context.evmVersion(),
-		identifierAccess
+		identifierAccess,
+		false,
+		m_optimiserSettings.optimizeStackAllocation
 	);
 	m_context.setStackOffset(startStackHeight);
 	return false;
@@ -983,7 +985,7 @@ void ContractCompiler::appendMissingFunctions()
 			{},
 			abiFunctions.second,
 			true,
-			m_optimiserSettings.runYulOptimiser
+			m_optimiserSettings
 		);
 }
 

libsolidity/interface/CompilerStack.cpp

@@ -993,7 +993,11 @@ string CompilerStack::createMetadata(Contract const& _contract) const
 		details["cse"] = m_optimiserSettings.runCSE;
 		details["constantOptimizer"] = m_optimiserSettings.runConstantOptimiser;
 		details["yul"] = m_optimiserSettings.runYulOptimiser;
-		details["yulDetails"] = Json::objectValue;
+		if (m_optimiserSettings.runYulOptimiser)
+		{
+			details["yulDetails"] = Json::objectValue;
+			details["yulDetails"]["stackAllocation"] = m_optimiserSettings.optimizeStackAllocation;
+		}
 
 		meta["settings"]["optimizer"]["details"] = std::move(details);
 	}

libsolidity/interface/OptimiserSettings.h

@@ -54,15 +54,17 @@ struct OptimiserSettings
 		s.runDeduplicate = true;
 		s.runCSE = true;
 		s.runConstantOptimiser = true;
-		// The only disabled one
+		// The only disabled ones
+		s.optimizeStackAllocation = false;
 		s.runYulOptimiser = false;
 		s.expectedExecutionsPerDeployment = 200;
 		return s;
 	}
-	/// Standard optimisations plus yul optimiser.
+	/// Standard optimisations plus yul and stack optimiser.
 	static OptimiserSettings full()
 	{
 		OptimiserSettings s = enabled();
+		s.optimizeStackAllocation = true;
 		s.runYulOptimiser = true;
 		return s;
 	}
@@ -76,6 +78,7 @@ struct OptimiserSettings
 			runDeduplicate == _other.runDeduplicate &&
 			runCSE == _other.runCSE &&
 			runConstantOptimiser == _other.runConstantOptimiser &&
+			optimizeStackAllocation == _other.optimizeStackAllocation &&
 			runYulOptimiser == _other.runYulOptimiser &&
 			expectedExecutionsPerDeployment == _other.expectedExecutionsPerDeployment;
 	}
@@ -94,6 +97,8 @@ struct OptimiserSettings
 	/// Constant optimizer, which tries to find better representations that satisfy the given
 	/// size/cost-trade-off.
 	bool runConstantOptimiser = false;
+	/// Perform more efficient stack allocation for variables during code generation from Yul to bytecode.
+	bool optimizeStackAllocation = false;
 	/// Yul optimiser with default settings. Will only run on certain parts of the code for now.
 	bool runYulOptimiser = false;
 	/// This specifies an estimate on how often each opcode in this assembly will be executed,

libsolidity/interface/StandardCompiler.cpp

@@ -399,12 +399,17 @@ boost::variant<OptimiserSettings, Json::Value> parseOptimizerSettings(Json::Valu
 			return *error;
 		if (auto error = checkOptimizerDetail(details, "yul", settings.runYulOptimiser))
 			return *error;
+		if (settings.runYulOptimiser)
+			settings.optimizeStackAllocation = true;
 		if (details.isMember("yulDetails"))
 		{
-			if (!_jsonInput["yulDetails"].isObject())
-				return formatFatalError("JSONError", "The \"yulDetails\" optimizer setting has to be a JSON object.");
-			if (!_jsonInput["yulDetails"].getMemberNames().empty())
-				return formatFatalError("JSONError", "The \"yulDetails\" optimizer setting cannot have any settings yet.");
+			if (!settings.runYulOptimiser)
+				return formatFatalError("JSONError", "\"Providing yulDetails requires Yul optimizer to be enabled.");
+
+			if (auto result = checkKeys(details["yulDetails"], {"stackAllocation"}, "settings.optimizer.details.yulDetails"))
+				return *result;
+			if (auto error = checkOptimizerDetail(details["yulDetails"], "stackAllocation", settings.optimizeStackAllocation))
+				return *error;
 		}
 	}
 	return std::move(settings);

libyul/backends/evm/AsmCodeGen.cpp

@@ -180,7 +180,7 @@ void CodeGenerator::assemble(
 	langutil::EVMVersion _evmVersion,
 	ExternalIdentifierAccess const& _identifierAccess,
 	bool _useNamedLabelsForFunctions,
-	bool _optimize
+	bool _optimizeStackAllocation
 )
 {
 	EthAssemblyAdapter assemblyAdapter(_assembly);
@@ -190,7 +190,7 @@ void CodeGenerator::assemble(
 		_analysisInfo,
 		_parsedData,
 		*dialect,
-		_optimize,
+		_optimizeStackAllocation,
 		false,
 		_identifierAccess,
 		_useNamedLabelsForFunctions

libyul/backends/evm/AsmCodeGen.h

@@ -82,7 +82,7 @@ public:
 		langutil::EVMVersion _evmVersion,
 		ExternalIdentifierAccess const& _identifierAccess = ExternalIdentifierAccess(),
 		bool _useNamedLabelsForFunctions = false,
-		bool _optimize = false
+		bool _optimizeStackAllocation = false
 	);
 };
 

solc/CommandLineInterface.cpp

@@ -907,6 +907,7 @@ bool CommandLineInterface::processInput()
 		OptimiserSettings settings = m_args.count(g_argOptimize) ? OptimiserSettings::enabled() : OptimiserSettings::minimal();
 		settings.expectedExecutionsPerDeployment = m_args[g_argOptimizeRuns].as<unsigned>();
 		settings.runYulOptimiser = m_args.count(g_strOptimizeYul);
+		settings.optimizeStackAllocation = settings.runYulOptimiser;
 		m_compiler->setOptimiserSettings(settings);
 
 		bool successful = m_compiler->compile();

test/cmdlineTests/standard_optimizer_yulDetails_no_object/input.json

@@ -10,7 +10,7 @@
 	"settings":
 	{
 		"optimizer": {
-			"details": { "yulDetails": 7 }
+			"details": { "yul": true, "yulDetails": 7 }
 		}
 	}
 }

test/cmdlineTests/standard_optimizer_yulDetails_no_object/output.json

@@ -1 +1 @@
-{"errors":[{"component":"general","formattedMessage":"The \"yulDetails\" optimizer setting has to be a JSON object.","message":"The \"yulDetails\" optimizer setting has to be a JSON object.","severity":"error","type":"JSONError"}]}
+{"errors":[{"component":"general","formattedMessage":"\"settings.optimizer.details.yulDetails\" must be an object","message":"\"settings.optimizer.details.yulDetails\" must be an object","severity":"error","type":"JSONError"}]}

test/cmdlineTests/standard_optimizer_yulDetails_without_yul/input.json

@@ -0,0 +1,16 @@
+{
+	"language": "Solidity",
+	"sources":
+	{
+		"A":
+		{
+			"content": "pragma solidity >=0.0; contract C { function f() public pure {} }"
+		}
+	},
+	"settings":
+	{
+		"optimizer": {
+			"details": { "yulDetails": 7 }
+		}
+	}
+}

test/cmdlineTests/standard_optimizer_yulDetails_without_yul/output.json

@@ -0,0 +1 @@
+{"errors":[{"component":"general","formattedMessage":"\"Providing yulDetails requires Yul optimizer to be enabled.","message":"\"Providing yulDetails requires Yul optimizer to be enabled.","severity":"error","type":"JSONError"}]}

test/libsolidity/StandardCompiler.cpp

@@ -1010,7 +1010,10 @@ BOOST_AUTO_TEST_CASE(optimizer_settings_details_different)
 	BOOST_CHECK(optimizer["details"]["jumpdestRemover"].asBool() == true);
 	BOOST_CHECK(optimizer["details"]["orderLiterals"].asBool() == false);
 	BOOST_CHECK(optimizer["details"]["peephole"].asBool() == true);
+	BOOST_CHECK(optimizer["details"]["yul"].asBool() == true);
 	BOOST_CHECK(optimizer["details"]["yulDetails"].isObject());
+	BOOST_CHECK(optimizer["details"]["yulDetails"].getMemberNames() == vector<string>{"stackAllocation"});
+	BOOST_CHECK(optimizer["details"]["yulDetails"]["stackAllocation"].asBool() == true);
 	BOOST_CHECK_EQUAL(optimizer["details"].getMemberNames().size(), 8);
 	BOOST_CHECK(optimizer["runs"].asUInt() == 600);
 }