Conditional unsimplifier

2023-10-03 13:03:40 +00:00 · 2019-11-01 14:01:56 +01:00
parent 21b9606ed3
commit 61a2d44f38
6 changed files with 205 additions and 77 deletions
@@ -0,0 +1,98 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include <libyul/optimiser/ConditionalUnsimplifier.h>
+#include <libyul/optimiser/Semantics.h>
+#include <libyul/AsmData.h>
+#include <libyul/Utilities.h>
+#include <libyul/optimiser/NameCollector.h>
+#include <libdevcore/CommonData.h>
+#include <libdevcore/Visitor.h>
+
+using namespace std;
+using namespace dev;
+using namespace yul;
+
+void ConditionalUnsimplifier::operator()(Switch& _switch)
+{
+	visit(*_switch.expression);
+	if (_switch.expression->type() != typeid(Identifier))
+	{
+		ASTModifier::operator()(_switch);
+		return;
+	}
+	YulString expr = boost::get<Identifier>(*_switch.expression).name;
+	for (auto& _case: _switch.cases)
+	{
+		if (_case.value)
+		{
+			(*this)(*_case.value);
+			if (
+				!_case.body.statements.empty() &&
+				_case.body.statements.front().type() == typeid(Assignment)
+			)
+			{
+				Assignment const& assignment = boost::get<Assignment>(_case.body.statements.front());
+				if (
+					assignment.variableNames.size() == 1 &&
+					assignment.variableNames.front().name == expr &&
+					assignment.value->type() == typeid(Literal) &&
+					valueOfLiteral(boost::get<Literal>(*assignment.value)) == valueOfLiteral(*_case.value)
+				)
+					_case.body.statements.erase(_case.body.statements.begin());
+			}
+		}
+		(*this)(_case.body);
+	}
+}
+
+void ConditionalUnsimplifier::operator()(Block& _block)
+{
+	iterateReplacingWindow<2>(
+		_block.statements,
+		[&](Statement& _stmt1, Statement& _stmt2) -> std::optional<vector<Statement>>
+		{
+			visit(_stmt1);
+			if (_stmt1.type() == typeid(If))
+			{
+				If& _if = boost::get<If>(_stmt1);
+				if (
+					_if.condition->type() == typeid(Identifier) &&
+					!_if.body.statements.empty()
+				)
+				{
+					YulString condition = boost::get<Identifier>(*_if.condition).name;
+					if (
+						_stmt2.type() == typeid(Assignment) &&
+						TerminationFinder(m_dialect).controlFlowKind(_if.body.statements.back()) !=
+							TerminationFinder::ControlFlow::FlowOut
+					)
+					{
+						Assignment const& assignment = boost::get<Assignment>(_stmt2);
+						if (
+							assignment.variableNames.size() == 1 &&
+							assignment.variableNames.front().name == condition &&
+							assignment.value->type() == typeid(Literal) &&
+							valueOfLiteral(boost::get<Literal>(*assignment.value)) == 0
+						)
+							return {make_vector<Statement>(std::move(_stmt1))};
+					}
+				}
+			}
+			return {};
+		}
+	);
+}