Skip resolving Keccak if AST contains msize.

Also a refactoring changing `m_optimizeMLoad` to `m_containsMSize`.

libyul/optimiser/LoadResolver.cpp

@@ -48,7 +48,7 @@ void LoadResolver::run(OptimiserStepContext& _context, Block& _ast)
 	LoadResolver{
 		_context.dialect,
 		SideEffectsPropagator::sideEffects(_context.dialect, CallGraphGenerator::callGraph(_ast)),
-		!containsMSize,
+		containsMSize,
 		_context.expectedExecutionsPerDeployment
 	}(_ast);
 }
@@ -66,7 +66,7 @@ void LoadResolver::visit(Expression& _e)
 				break;
 			}
 
-		if (funCall->functionName.name == m_dialect.hashFunction({}))
+		if (!m_containsMSize && funCall->functionName.name == m_dialect.hashFunction({}))
 			tryEvaluateKeccak(_e, funCall->arguments);
 	}
 }
@@ -87,7 +87,7 @@ void LoadResolver::tryResolve(
 			if (inScope(*value))
 				_e = Identifier{locationOf(_e), *value};
 	}
-	else if (m_optimizeMLoad && _location == StoreLoadLocation::Memory)
+	else if (!m_containsMSize && _location == StoreLoadLocation::Memory)
 		if (auto value = util::valueOrNullptr(m_memory, key))
 			if (inScope(*value))
 				_e = Identifier{locationOf(_e), *value};

libyul/optimiser/LoadResolver.h

@@ -50,11 +50,11 @@ private:
 	LoadResolver(
 		Dialect const& _dialect,
 		std::map<YulString, SideEffects> _functionSideEffects,
-		bool _optimizeMLoad,
+		bool _containsMSize,
 		std::optional<size_t> _expectedExecutionsPerDeployment
 	):
 		DataFlowAnalyzer(_dialect, std::move(_functionSideEffects)),
-		m_optimizeMLoad(_optimizeMLoad),
+		m_containsMSize(_containsMSize),
 		m_expectedExecutionsPerDeployment(std::move(_expectedExecutionsPerDeployment))
 	{}
 
@@ -75,7 +75,8 @@ protected:
 		std::vector<Expression> const& _arguments
 	);
 
-	bool m_optimizeMLoad = false;
+	/// If the AST contains `msize`, then we skip resolving `mload` and `keccak256`.
+	bool m_containsMSize = false;
 	/// The --optimize-runs parameter. Value `nullopt` represents creation code.
 	std::optional<size_t> m_expectedExecutionsPerDeployment;
 };

test/libyul/yulOptimizerTests/loadResolver/keccak_with_msize.yul

@@ -0,0 +1,19 @@
+{
+    sstore(0, msize())
+    mstore(0, 10)
+    // Keccak-256 should not be evaluated because of the msize.
+    // Even though, though the code is likely equivalent,
+    // we skip steps if `msize` is present
+    let val := keccak256(0, 32)
+    sstore(1, val)
+}
+// ----
+// step: loadResolver
+//
+// {
+//     let _1 := msize()
+//     let _2 := 0
+//     sstore(_2, _1)
+//     mstore(_2, 10)
+//     sstore(1, keccak256(_2, 32))
+// }