Liveness: Add block exit values to live set for op-wise sets

Author: clonker

libyul/backends/evm/SSACFGLiveness.cpp

@@ -37,6 +37,29 @@ constexpr auto literalsFilter(SSACFG const& _cfg)
 }
 }
 
+std::set<SSACFG::ValueId> SSACFGLiveness::blockExitValues(SSACFG::BlockId const& _blockId) const
+{
+	std::set<SSACFG::ValueId> result;
+	util::GenericVisitor exitVisitor {
+		[](SSACFG::BasicBlock::MainExit const&) {},
+		[&](SSACFG::BasicBlock::FunctionReturn const& _functionReturn) {
+			result += _functionReturn.returnValues | ranges::views::filter(literalsFilter(m_cfg));
+		},
+		[&](SSACFG::BasicBlock::JumpTable const& _jt) {
+			if (literalsFilter(m_cfg)(_jt.value))
+				result.emplace(_jt.value);
+		},
+		[](SSACFG::BasicBlock::Jump const&) {},
+		[&](SSACFG::BasicBlock::ConditionalJump const& _conditionalJump) {
+			if (literalsFilter(m_cfg)(_conditionalJump.condition))
+				result.emplace(_conditionalJump.condition);
+		},
+		[](SSACFG::BasicBlock::Terminated const&) {}
+	};
+	std::visit(exitVisitor, m_cfg.block(_blockId).exit);
+	return result;
+}
+
 SSACFGLiveness::SSACFGLiveness(SSACFG const& _cfg):
 	m_cfg(_cfg),
 	m_topologicalSort(_cfg),
@@ -70,12 +93,7 @@ void SSACFGLiveness::runDagDfs()
 				{
 					auto const& info = m_cfg.valueInfo(phi);
 					yulAssert(std::holds_alternative<SSACFG::PhiValue>(info), "value info of phi wasn't PhiValue");
-					auto const& entries = m_cfg.block(std::get<SSACFG::PhiValue>(info).block).entries;
-					// this is getting the argument index of the phi function corresponding to the path going
-					// through "blockId", ie, the currently handled block
-					auto const it = entries.find(blockId);
-					yulAssert(it != entries.end());
-					auto const argIndex = static_cast<size_t>(std::distance(entries.begin(), it));
+					auto const argIndex = m_cfg.phiArgumentIndex(blockId, _successor);
 					yulAssert(argIndex < std::get<SSACFG::PhiValue>(info).arguments.size());
 					auto const arg = std::get<SSACFG::PhiValue>(info).arguments.at(argIndex);
 					if (!std::holds_alternative<SSACFG::LiteralValue>(m_cfg.valueInfo(arg)))
@@ -103,23 +121,7 @@ void SSACFGLiveness::runDagDfs()
 		// for each program point p in B, backwards, do:
 		{
 			// add value ids to the live set that are used in exit blocks
-			util::GenericVisitor exitVisitor {
-				[](SSACFG::BasicBlock::MainExit const&) {},
-				[&](SSACFG::BasicBlock::FunctionReturn const& _functionReturn) {
-					live += _functionReturn.returnValues | ranges::views::filter(literalsFilter(m_cfg));
-				},
-				[&](SSACFG::BasicBlock::JumpTable const& _jt) {
-					if (literalsFilter(m_cfg)(_jt.value))
-						live.emplace(_jt.value);
-				},
-				[](SSACFG::BasicBlock::Jump const&) {},
-				[&](SSACFG::BasicBlock::ConditionalJump const& _conditionalJump) {
-					if (literalsFilter(m_cfg)(_conditionalJump.condition))
-						live.emplace(_conditionalJump.condition);
-				},
-				[](SSACFG::BasicBlock::Terminated const&) {}
-			};
-			std::visit(exitVisitor, block.exit);
+			live += blockExitValues(blockId);
 
 			for (auto const& op: block.operations | ranges::views::reverse)
 			{
@@ -163,12 +165,13 @@ void SSACFGLiveness::fillOperationsLiveOut()
 {
 	for (size_t blockIdValue = 0; blockIdValue < m_cfg.numBlocks(); ++blockIdValue)
 	{
-		auto const& operations = m_cfg.block(SSACFG::BlockId{blockIdValue}).operations;
+		SSACFG::BlockId const blockId{blockIdValue};
+		auto const& operations = m_cfg.block(blockId).operations;
 		auto& liveOuts = m_operationLiveOuts[blockIdValue];
 		liveOuts.resize(operations.size());
 		if (!operations.empty())
 		{
-			auto live = m_liveOuts[blockIdValue];
+			auto live = m_liveOuts[blockIdValue] + blockExitValues(blockId);
 			auto rit = liveOuts.rbegin();
 			for (auto const& op: operations | ranges::views::reverse)
 			{

libyul/backends/evm/SSACFGLiveness.h

@@ -47,6 +47,7 @@ class SSACFGLiveness
 	void runDagDfs();
 	void runLoopTreeDfs(size_t _loopHeader);
 	void fillOperationsLiveOut();
+	std::set<SSACFG::ValueId> blockExitValues(SSACFG::BlockId const& _blockId) const;
 
 	SSACFG const& m_cfg;
 	ForwardSSACFGTopologicalSort m_topologicalSort;

libyul/backends/evm/SSAControlFlowGraph.h

@@ -76,7 +76,7 @@ class SSACFG
 		langutil::DebugData::ConstPtr debugData;
 		std::reference_wrapper<Scope::Function const> function;
 		std::reference_wrapper<FunctionCall const> call;
-		bool const canContinue = true;
+		bool canContinue;
 	};
 
 	struct Operation {
@@ -162,6 +162,10 @@ class SSACFG
 	};
 	struct UnreachableValue {};
 	using ValueInfo = std::variant<UnreachableValue, VariableValue, LiteralValue, PhiValue>;
+	bool isLiteralValue(ValueId const _var) const
+	{
+		return std::holds_alternative<LiteralValue>(valueInfo(_var));
+	}
 	ValueInfo& valueInfo(ValueId const _var)
 	{
 		return m_valueInfos.at(_var.value);
@@ -208,6 +212,14 @@ class SSACFG
 		return it->second;
 	}
 
+	size_t phiArgumentIndex(BlockId const _source, BlockId const _target) const
+	{
+		auto const& targetBlock = block(_target);
+		auto idx = util::findOffset(targetBlock.entries, _source);
+		yulAssert(idx, fmt::format("Target block {} not found as entry in one of the exits of the current block {}.", _target.value, _source.value));
+		return *idx;
+	}
+
 	std::string toDot(
 		bool _includeDiGraphDefinition=true,
 		std::optional<size_t> _functionIndex=std::nullopt,