Enable fine grained yul optimizer fuzzing

test/libyul/YulOptimizerTest.cpp

@@ -74,7 +74,8 @@ TestCase::TestResult YulOptimizerTest::run(ostream& _stream, string const& _line
 	soltestAssert(m_dialect, "Dialect not set.");
 
 	m_object->analysisInfo = m_analysisInfo;
-	YulOptimizerTestCommon tester(m_object, *m_dialect, m_optimizerStep);
+	YulOptimizerTestCommon tester(m_object, *m_dialect);
+	tester.setStep(m_optimizerStep);
 
 	if (!tester.runStep())
 	{

test/libyul/YulOptimizerTestCommon.cpp

@@ -66,6 +66,8 @@
 
 #include <libsolidity/interface/OptimiserSettings.h>
 
+#include <random>
+
 using namespace solidity;
 using namespace solidity::util;
 using namespace solidity::langutil;
@@ -76,15 +78,13 @@ using namespace std;
 
 YulOptimizerTestCommon::YulOptimizerTestCommon(
 	shared_ptr<Object> _obj,
-	Dialect const& _dialect,
+	Dialect const& _dialect
-	string const& _optimizerStep
 )
 {
 	m_object = _obj;
 	m_ast = m_object->code;
 	m_analysisInfo = m_object->analysisInfo;
 	m_dialect = &_dialect;
-	m_optimizerStep = _optimizerStep;
 
 	m_namedSteps = {
 		{"disambiguator", [&]() { disambiguate(); }},
@@ -360,6 +360,11 @@ YulOptimizerTestCommon::YulOptimizerTestCommon(
 	};
 }
 
+void YulOptimizerTestCommon::setStep(string const& _optimizerStep)
+{
+	m_optimizerStep = _optimizerStep;
+}
+
 bool YulOptimizerTestCommon::runStep()
 {
 	yulAssert(m_dialect, "Dialect not set.");
@@ -374,6 +379,31 @@ bool YulOptimizerTestCommon::runStep()
 	return true;
 }
 
+string YulOptimizerTestCommon::randomOptimiserStep(unsigned _seed)
+{
+	std::mt19937 prng(_seed);
+	std::uniform_int_distribution<size_t> dist(1, m_namedSteps.size());
+	size_t idx = dist(prng);
+	size_t count = 1;
+	for (auto &step: m_namedSteps)
+	{
+		if (count == idx)
+		{
+			string optimiserStep = step.first;
+			// Do not fuzz mainFunction or wordSizeTransform
+			// because they do not preserve yul code semantics.
+			if (optimiserStep == "mainFunction" || optimiserStep == "wordSizeTransform")
+				// "Fullsuite" is fuzzed roughly three times more frequently than
+				// other steps because of the filtering in place above.
+				return "fullSuite";
+			else
+				return optimiserStep;
+		}
+		count++;
+	}
+	yulAssert(false, "Optimiser step selection failed.");
+}
+
 shared_ptr<Block> YulOptimizerTestCommon::run()
 {
 	return runStep() ? m_ast : nullptr;

test/libyul/YulOptimizerTestCommon.h

@@ -40,15 +40,22 @@ class YulOptimizerTestCommon
 public:
 	explicit YulOptimizerTestCommon(
 		std::shared_ptr<Object> _obj,
-		Dialect const& _dialect,
+		Dialect const& _dialect
-		std::string const& _optimizerStep
 	);
+	/// Sets optimiser step to be run to @param
+	/// _optimiserStep.
+	void setStep(std::string const& _optimizerStep);
 	/// Runs chosen optimiser step returning pointer
 	/// to yul AST Block post optimisation.
 	std::shared_ptr<Block> run();
 	/// Runs chosen optimiser step returning true if
 	/// successful, false otherwise.
 	bool runStep();
+	/// Returns the string name of a randomly chosen
+	/// optimiser step.
+	/// @param _seed is an unsigned integer that
+	/// seeds the random selection.
+	std::string randomOptimiserStep(unsigned _seed);
 private:
 	void disambiguate();
 	void updateContext();

test/tools/ossfuzz/CMakeLists.txt

@@ -76,7 +76,12 @@ if (OSSFUZZ)
     target_link_libraries(strictasm_assembly_ossfuzz PRIVATE yul)
     set_target_properties(strictasm_assembly_ossfuzz PROPERTIES LINK_FLAGS ${LIB_FUZZING_ENGINE})
 
-    add_executable(yul_proto_ossfuzz yulProtoFuzzer.cpp protoToYul.cpp yulProto.pb.cc)
+    add_executable(yul_proto_ossfuzz
+	    yulProtoFuzzer.cpp
+	    protoToYul.cpp
+	    yulProto.pb.cc
+	    ../../libyul/YulOptimizerTestCommon.cpp
+    )
     target_include_directories(yul_proto_ossfuzz PRIVATE /usr/include/libprotobuf-mutator)
     target_link_libraries(yul_proto_ossfuzz PRIVATE yul
             protobuf-mutator-libfuzzer.a
@@ -86,7 +91,14 @@ if (OSSFUZZ)
     set_target_properties(yul_proto_ossfuzz PROPERTIES LINK_FLAGS ${LIB_FUZZING_ENGINE})
     target_compile_options(yul_proto_ossfuzz PUBLIC ${COMPILE_OPTIONS} -Wno-sign-conversion -Wno-suggest-destructor-override -Wno-inconsistent-missing-destructor-override)
 
-    add_executable(yul_proto_diff_ossfuzz yulProto_diff_ossfuzz.cpp yulFuzzerCommon.cpp protoToYul.cpp yulProto.pb.cc)
+    add_executable(
+	    yul_proto_diff_ossfuzz
+	    yulProto_diff_ossfuzz.cpp
+	    yulFuzzerCommon.cpp
+	    protoToYul.cpp
+	    yulProto.pb.cc
+	    ../../libyul/YulOptimizerTestCommon.cpp
+    )
     target_include_directories(yul_proto_diff_ossfuzz PRIVATE /usr/include/libprotobuf-mutator)
     target_link_libraries(yul_proto_diff_ossfuzz PRIVATE yul
             yulInterpreter
@@ -103,6 +115,7 @@ if (OSSFUZZ)
             protoToYul.cpp
             yulProto.pb.cc
             protomutators/YulProtoMutator.cpp
+            ../../libyul/YulOptimizerTestCommon.cpp
     )
     target_include_directories(yul_proto_diff_custom_mutate_ossfuzz PRIVATE /usr/include/libprotobuf-mutator)
     target_link_libraries(yul_proto_diff_custom_mutate_ossfuzz PRIVATE yul

test/tools/ossfuzz/protoToYul.h

@@ -64,7 +64,6 @@ public:
 	{
 		return m_evmVersion;
 	}
-
 private:
 	void visit(BinaryOp const&);
 

test/tools/ossfuzz/yulProto.proto

@@ -415,6 +415,7 @@ message Program {
     Object obj = 2;
   }
   required Version ver = 3;
+  required uint32 step = 4;
 }
 
 package solidity.yul.test.yul_fuzzer;

test/tools/ossfuzz/yulProtoFuzzer.cpp

@@ -19,16 +19,24 @@
 #include <fstream>
 
 #include <test/tools/ossfuzz/yulProto.pb.h>
-#include <test/tools/fuzzer_common.h>
 #include <test/tools/ossfuzz/protoToYul.h>
-#include <src/libfuzzer/libfuzzer_macro.h>
+
+#include <test/tools/fuzzer_common.h>
+
+#include <test/libyul/YulOptimizerTestCommon.h>
 
 #include <libyul/AssemblyStack.h>
-#include <liblangutil/EVMVersion.h>
 #include <libyul/Exceptions.h>
 
+#include <libyul/backends/evm/EVMDialect.h>
+
+#include <liblangutil/EVMVersion.h>
+
+#include <src/libfuzzer/libfuzzer_macro.h>
+
 using namespace solidity;
 using namespace solidity::yul;
+using namespace solidity::yul::test;
 using namespace solidity::yul::test::yul_fuzzer;
 using namespace solidity::langutil;
 using namespace std;
@@ -69,5 +77,11 @@ DEFINE_PROTO_FUZZER(Program const& _input)
 		yulAssert(false, "Proto fuzzer generated malformed program");
 
 	// Optimize
-	stack.optimize();
+	YulOptimizerTestCommon optimizerTest(
+		stack.parserResult(),
+		EVMDialect::strictAssemblyForEVMObjects(version)
+	);
+	optimizerTest.setStep(optimizerTest.randomOptimiserStep(_input.step()));
+	shared_ptr<solidity::yul::Block> astBlock = optimizerTest.run();
+	yulAssert(astBlock != nullptr, "Optimiser error.");
 }

test/tools/ossfuzz/yulProto_diff_ossfuzz.cpp

@@ -21,6 +21,9 @@
 #include <test/tools/ossfuzz/yulProto.pb.h>
 #include <test/tools/fuzzer_common.h>
 #include <test/tools/ossfuzz/protoToYul.h>
+
+#include <test/libyul/YulOptimizerTestCommon.h>
+
 #include <src/libfuzzer/libfuzzer_macro.h>
 
 #include <libyul/AssemblyStack.h>
@@ -104,10 +107,16 @@ DEFINE_PROTO_FUZZER(Program const& _input)
 	)
 		return;
 
-	stack.optimize();
+	YulOptimizerTestCommon optimizerTest(
+		stack.parserResult(),
+		EVMDialect::strictAssemblyForEVMObjects(version)
+	);
+	optimizerTest.setStep(optimizerTest.randomOptimiserStep(_input.step()));
+	shared_ptr<solidity::yul::Block> astBlock = optimizerTest.run();
+	yulAssert(astBlock != nullptr, "Optimiser error.");
 	termReason = yulFuzzerUtil::interpret(
 		os2,
-		stack.parserResult()->code,
+		astBlock,
 		EVMDialect::strictAssemblyForEVMObjects(version)
 	);
 	if (