From 5449ad3c5212a8ffacb57e8d66712e66bd798242 Mon Sep 17 00:00:00 2001
From: Daniel Kirchner <daniel@ekpyron.org>
Date: Mon, 9 Aug 2021 18:59:29 +0200
Subject: [PATCH] A first stack shuffling unit test.

---
 test/CMakeLists.txt                |  1 +
 test/libyul/StackShufflingTest.cpp | 83 ++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 test/libyul/StackShufflingTest.cpp

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index f35660741..2c3615904 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -145,6 +145,7 @@ set(libyul_sources
     libyul/Parser.cpp
     libyul/StackLayoutGeneratorTest.cpp
     libyul/StackLayoutGeneratorTest.h
+    libyul/StackShufflingTest.cpp
     libyul/SyntaxTest.h
     libyul/SyntaxTest.cpp
     libyul/YulInterpreterTest.cpp
diff --git a/test/libyul/StackShufflingTest.cpp b/test/libyul/StackShufflingTest.cpp
new file mode 100644
index 000000000..f33134318
--- /dev/null
+++ b/test/libyul/StackShufflingTest.cpp
@@ -0,0 +1,83 @@
+/*
+    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/>.
+*/
+/**
+ * Unit tests for stack shuffling.
+ */
+#include <test/Common.h>
+
+#include <libyul/backends/evm/StackHelpers.h>
+#include <libyul/backends/evm/OptimizedEVMCodeTransform.h>
+
+#include <boost/test/unit_test.hpp>
+
+using namespace std;
+
+namespace solidity::yul::test
+{
+
+BOOST_AUTO_TEST_SUITE(StackHelpers)
+
+BOOST_AUTO_TEST_CASE(avoid_deep_dup)
+{
+	vector<Scope::Variable> variableContainer;
+	for (size_t i = 0; i < 15; ++i)
+		variableContainer.emplace_back(Scope::Variable{YulString{}, YulString("v" + to_string(i))});
+	Stack from = {{
+		VariableSlot{variableContainer[0]},
+		VariableSlot{variableContainer[1]},
+		VariableSlot{variableContainer[2]},
+		VariableSlot{variableContainer[3]},
+		VariableSlot{variableContainer[4]},
+		VariableSlot{variableContainer[5]},
+		VariableSlot{variableContainer[6]},
+		VariableSlot{variableContainer[7]},
+		VariableSlot{variableContainer[8]},
+		VariableSlot{variableContainer[9]},
+		VariableSlot{variableContainer[10]},
+		VariableSlot{variableContainer[11]},
+		VariableSlot{variableContainer[12]},
+		VariableSlot{variableContainer[12]},
+		VariableSlot{variableContainer[13]},
+		VariableSlot{variableContainer[14]}
+	}};
+	Stack to = {{
+		VariableSlot{variableContainer[0]},
+		VariableSlot{variableContainer[1]},
+		VariableSlot{variableContainer[2]},
+		VariableSlot{variableContainer[3]},
+		VariableSlot{variableContainer[4]},
+		VariableSlot{variableContainer[5]},
+		VariableSlot{variableContainer[6]},
+		VariableSlot{variableContainer[7]},
+		VariableSlot{variableContainer[8]},
+		VariableSlot{variableContainer[9]},
+		VariableSlot{variableContainer[10]},
+		VariableSlot{variableContainer[11]},
+		VariableSlot{variableContainer[12]},
+		VariableSlot{variableContainer[12]},
+		VariableSlot{variableContainer[13]},
+		VariableSlot{variableContainer[14]},
+		VariableSlot{variableContainer[14]}, // While "optimal", bringing this slot up first will make the next unreachable.
+		VariableSlot{variableContainer[0]}
+	}};
+	auto unreachable = OptimizedEVMCodeTransform::tryCreateStackLayout(from, to, {});
+	BOOST_CHECK(unreachable.empty());
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+
+} // end namespaces