Fix removal of memory stores in inline assembly blocks.

Author: chriseth

Changelog.md

@@ -1,5 +1,9 @@
 ### 0.8.15 (unreleased)
 
+Important Bugfixes:
+ * Yul Optimizer: Keep all memory side-effects of inline assembly blocks.
+
+
 Language Features:
  * Add `E.selector` for a non-anonymous event `E` to access the 32-byte selector topic.
  * Errors and Events allow qualified access from other contracts.

libsolidity/codegen/CompilerContext.cpp

@@ -485,6 +485,7 @@ void CompilerContext::appendInlineAssembly(
 		obj.code = parserResult;
 		obj.analysisInfo = make_shared<yul::AsmAnalysisInfo>(analysisInfo);
 
+		solAssert(!dialect.providesObjectAccess());
 		optimizeYul(obj, dialect, _optimiserSettings, externallyUsedIdentifiers);
 
 		if (_system)

libyul/optimiser/UnusedStoreEliminator.cpp

@@ -31,6 +31,8 @@
 #include <libyul/ControlFlowSideEffectsCollector.h>
 #include <libyul/AST.h>
 
+#include <libyul/backends/evm/EVMDialect.h>
+
 #include <libsolutil/CommonData.h>
 
 #include <libevmasm/Instruction.h>
@@ -76,7 +78,13 @@ void UnusedStoreEliminator::run(OptimiserStepContext& _context, Block& _ast)
 		ignoreMemory
 	};
 	rse(_ast);
-	rse.changeUndecidedTo(State::Unused, Location::Memory);
+	if (
+		auto evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
+		evmDialect && evmDialect->providesObjectAccess()
+	)
+		rse.changeUndecidedTo(State::Unused, Location::Memory);
+	else
+		rse.changeUndecidedTo(State::Used, Location::Memory);
 	rse.changeUndecidedTo(State::Used, Location::Storage);
 	rse.scheduleUnusedForDeletion();
 

test/libsolidity/semanticTests/array/pop/byte_array_pop_long_storage_empty_garbage_ref.sol

@@ -17,5 +17,5 @@ contract c {
 // test() ->
 // gas irOptimized: 142639
 // gas legacy: 164430
-// gas legacyOptimized: 157898
+// gas legacyOptimized: 158513
 // storageEmpty -> 1