solidity/test/libevmasm/Optimiser.cpp

/*
	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/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2014
 * Tests for the Solidity optimizer.
 */

#include <libevmasm/CommonSubexpressionEliminator.h>
#include <libevmasm/PeepholeOptimiser.h>
#include <libevmasm/ControlFlowGraph.h>
#include <libevmasm/BlockDeduplicator.h>
#include <libevmasm/Assembly.h>

#include <boost/test/unit_test.hpp>
#include <boost/lexical_cast.hpp>

#include <string>
#include <tuple>
#include <memory>

using namespace std;
using namespace dev::eth;

namespace dev
{
namespace solidity
{
namespace test
{

namespace
{
	AssemblyItems addDummyLocations(AssemblyItems const& _input)
	{
		// add dummy locations to each item so that we can check that they are not deleted
		AssemblyItems input = _input;
		for (AssemblyItem& item: input)
			item.setLocation(SourceLocation(1, 3, make_shared<string>("")));
		return input;
	}

	eth::KnownState createInitialState(AssemblyItems const& _input)
	{
		eth::KnownState state;
		for (auto const& item: addDummyLocations(_input))
			state.feedItem(item, true);
		return state;
	}

	AssemblyItems CSE(AssemblyItems const& _input, eth::KnownState const& _state = eth::KnownState())
	{
		AssemblyItems input = addDummyLocations(_input);

		eth::CommonSubexpressionEliminator cse(_state);
		BOOST_REQUIRE(cse.feedItems(input.begin(), input.end()) == input.end());
		AssemblyItems output = cse.getOptimizedItems();

		for (AssemblyItem const& item: output)
		{
			BOOST_CHECK(item == Instruction::POP || !item.location().isEmpty());
		}
		return output;
	}

	void checkCSE(
		AssemblyItems const& _input,
		AssemblyItems const& _expectation,
		KnownState const& _state = eth::KnownState()
	)
	{
		AssemblyItems output = CSE(_input, _state);
		BOOST_CHECK_EQUAL_COLLECTIONS(_expectation.begin(), _expectation.end(), output.begin(), output.end());
	}

	AssemblyItems CFG(AssemblyItems const& _input)
	{
		AssemblyItems output = _input;
		// Running it four times should be enough for these tests.
		for (unsigned i = 0; i < 4; ++i)
		{
			ControlFlowGraph cfg(output);
			AssemblyItems optItems;
			for (BasicBlock const& block: cfg.optimisedBlocks())
				copy(output.begin() + block.begin, output.begin() + block.end,
					 back_inserter(optItems));
			output = move(optItems);
		}
		return output;
	}

	void checkCFG(AssemblyItems const& _input, AssemblyItems const& _expectation)
	{
		AssemblyItems output = CFG(_input);
		BOOST_CHECK_EQUAL_COLLECTIONS(_expectation.begin(), _expectation.end(), output.begin(), output.end());
	}
}

BOOST_AUTO_TEST_SUITE(Optimiser)

BOOST_AUTO_TEST_CASE(cse_intermediate_swap)
{
	eth::KnownState state;
	eth::CommonSubexpressionEliminator cse(state);
	AssemblyItems input{
		Instruction::SWAP1, Instruction::POP, Instruction::ADD, u256(0), Instruction::SWAP1,
		Instruction::SLOAD, Instruction::SWAP1, u256(100), Instruction::EXP, Instruction::SWAP1,
		Instruction::DIV, u256(0xff), Instruction::AND
	};
	BOOST_REQUIRE(cse.feedItems(input.begin(), input.end()) == input.end());
	AssemblyItems output = cse.getOptimizedItems();
	BOOST_CHECK(!output.empty());
}

BOOST_AUTO_TEST_CASE(cse_negative_stack_access)
{
	AssemblyItems input{Instruction::DUP2, u256(0)};
	checkCSE(input, input);
}

BOOST_AUTO_TEST_CASE(cse_negative_stack_end)
{
	AssemblyItems input{Instruction::ADD};
	checkCSE(input, input);
}

BOOST_AUTO_TEST_CASE(cse_intermediate_negative_stack)
{
	AssemblyItems input{Instruction::ADD, u256(1), Instruction::DUP1};
	checkCSE(input, input);
}

BOOST_AUTO_TEST_CASE(cse_pop)
{
	checkCSE({Instruction::POP}, {Instruction::POP});
}

BOOST_AUTO_TEST_CASE(cse_unneeded_items)
{
	AssemblyItems input{
		Instruction::ADD,
		Instruction::SWAP1,
		Instruction::POP,
		u256(7),
		u256(8),
	};
	checkCSE(input, input);
}

BOOST_AUTO_TEST_CASE(cse_constant_addition)
{
	AssemblyItems input{u256(7), u256(8), Instruction::ADD};
	checkCSE(input, {u256(7 + 8)});
}

BOOST_AUTO_TEST_CASE(cse_invariants)
{
	AssemblyItems input{
		Instruction::DUP1,
		Instruction::DUP1,
		u256(0),
		Instruction::OR,
		Instruction::OR
	};
	checkCSE(input, {Instruction::DUP1});
}

BOOST_AUTO_TEST_CASE(cse_subself)
{
	checkCSE({Instruction::DUP1, Instruction::SUB}, {Instruction::POP, u256(0)});
}

BOOST_AUTO_TEST_CASE(cse_subother)
{
	checkCSE({Instruction::SUB}, {Instruction::SUB});
}

BOOST_AUTO_TEST_CASE(cse_double_negation)
{
	checkCSE({Instruction::DUP5, Instruction::NOT, Instruction::NOT}, {Instruction::DUP5});
}

BOOST_AUTO_TEST_CASE(cse_double_iszero)
{
	checkCSE({Instruction::GT, Instruction::ISZERO, Instruction::ISZERO}, {Instruction::GT});
	checkCSE({Instruction::GT, Instruction::ISZERO}, {Instruction::GT, Instruction::ISZERO});
	checkCSE(
		{Instruction::ISZERO, Instruction::ISZERO, Instruction::ISZERO},
		{Instruction::ISZERO}
	);
}

BOOST_AUTO_TEST_CASE(cse_associativity)
{
	AssemblyItems input{
		Instruction::DUP1,
		Instruction::DUP1,
		u256(0),
		Instruction::OR,
		Instruction::OR
	};
	checkCSE(input, {Instruction::DUP1});
}

BOOST_AUTO_TEST_CASE(cse_associativity2)
{
	AssemblyItems input{
		u256(0),
		Instruction::DUP2,
		u256(2),
		u256(1),
		Instruction::DUP6,
		Instruction::ADD,
		u256(2),
		Instruction::ADD,
		Instruction::ADD,
		Instruction::ADD,
		Instruction::ADD
	};
	checkCSE(input, {Instruction::DUP2, Instruction::DUP2, Instruction::ADD, u256(5), Instruction::ADD});
}

BOOST_AUTO_TEST_CASE(cse_storage)
{
	AssemblyItems input{
		u256(0),
		Instruction::SLOAD,
		u256(0),
		Instruction::SLOAD,
		Instruction::ADD,
		u256(0),
		Instruction::SSTORE
	};
	checkCSE(input, {
		u256(0),
		Instruction::DUP1,
		Instruction::SLOAD,
		Instruction::DUP1,
		Instruction::ADD,
		Instruction::SWAP1,
		Instruction::SSTORE
	});
}

BOOST_AUTO_TEST_CASE(cse_noninterleaved_storage)
{
	// two stores to the same location should be replaced by only one store, even if we
	// read in the meantime
	AssemblyItems input{
		u256(7),
		Instruction::DUP2,
		Instruction::SSTORE,
		Instruction::DUP1,
		Instruction::SLOAD,
		u256(8),
		Instruction::DUP3,
		Instruction::SSTORE
	};
	checkCSE(input, {
		u256(8),
		Instruction::DUP2,
		Instruction::SSTORE,
		u256(7)
	});
}

BOOST_AUTO_TEST_CASE(cse_interleaved_storage)
{
	// stores and reads to/from two unknown locations, should not optimize away the first store
	AssemblyItems input{
		u256(7),
		Instruction::DUP2,
		Instruction::SSTORE, // store to "DUP1"
		Instruction::DUP2,
		Instruction::SLOAD, // read from "DUP2", might be equal to "DUP1"
		u256(0),
		Instruction::DUP3,
		Instruction::SSTORE // store different value to "DUP1"
	};
	checkCSE(input, input);
}

BOOST_AUTO_TEST_CASE(cse_interleaved_storage_same_value)
{
	// stores and reads to/from two unknown locations, should not optimize away the first store
	// but it should optimize away the second, since we already know the value will be the same
	AssemblyItems input{
		u256(7),
		Instruction::DUP2,
		Instruction::SSTORE, // store to "DUP1"
		Instruction::DUP2,
		Instruction::SLOAD, // read from "DUP2", might be equal to "DUP1"
		u256(6),
		u256(1),
		Instruction::ADD,
		Instruction::DUP3,
		Instruction::SSTORE // store same value to "DUP1"
	};
	checkCSE(input, {
		u256(7),
		Instruction::DUP2,
		Instruction::SSTORE,
		Instruction::DUP2,
		Instruction::SLOAD
	});
}

BOOST_AUTO_TEST_CASE(cse_interleaved_storage_at_known_location)
{
	// stores and reads to/from two known locations, should optimize away the first store,
	// because we know that the location is different
	AssemblyItems input{
		u256(0x70),
		u256(1),
		Instruction::SSTORE, // store to 1
		u256(2),
		Instruction::SLOAD, // read from 2, is different from 1
		u256(0x90),
		u256(1),
		Instruction::SSTORE // store different value at 1
	};
	checkCSE(input, {
		u256(2),
		Instruction::SLOAD,
		u256(0x90),
		u256(1),
		Instruction::SSTORE
	});
}

BOOST_AUTO_TEST_CASE(cse_interleaved_storage_at_known_location_offset)
{
	// stores and reads to/from two locations which are known to be different,
	// should optimize away the first store, because we know that the location is different
	AssemblyItems input{
		u256(0x70),
		Instruction::DUP2,
		u256(1),
		Instruction::ADD,
		Instruction::SSTORE, // store to "DUP1"+1
		Instruction::DUP1,
		u256(2),
		Instruction::ADD,
		Instruction::SLOAD, // read from "DUP1"+2, is different from "DUP1"+1
		u256(0x90),
		Instruction::DUP3,
		u256(1),
		Instruction::ADD,
		Instruction::SSTORE // store different value at "DUP1"+1
	};
	checkCSE(input, {
		u256(2),
		Instruction::DUP2,
		Instruction::ADD,
		Instruction::SLOAD,
		u256(0x90),
		u256(1),
		Instruction::DUP4,
		Instruction::ADD,
		Instruction::SSTORE
	});
}

BOOST_AUTO_TEST_CASE(cse_deep_stack)
{
	AssemblyItems input{
		Instruction::ADD,
		Instruction::SWAP1,
		Instruction::POP,
		Instruction::SWAP8,
		Instruction::POP,
		Instruction::SWAP8,
		Instruction::POP,
		Instruction::SWAP8,
		Instruction::SWAP5,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
	};
	checkCSE(input, {
		Instruction::SWAP4,
		Instruction::SWAP12,
		Instruction::SWAP3,
		Instruction::SWAP11,
		Instruction::POP,
		Instruction::SWAP1,
		Instruction::SWAP3,
		Instruction::ADD,
		Instruction::SWAP8,
		Instruction::POP,
		Instruction::SWAP6,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
		Instruction::POP,
	});
}

BOOST_AUTO_TEST_CASE(cse_jumpi_no_jump)
{
	AssemblyItems input{
		u256(0),
		u256(1),
		Instruction::DUP2,
		AssemblyItem(PushTag, 1),
		Instruction::JUMPI
	};
	checkCSE(input, {
		u256(0),
		u256(1)
	});
}

BOOST_AUTO_TEST_CASE(cse_jumpi_jump)
{
	AssemblyItems input{
		u256(1),
		u256(1),
		Instruction::DUP2,
		AssemblyItem(PushTag, 1),
		Instruction::JUMPI
	};
	checkCSE(input, {
		u256(1),
		Instruction::DUP1,
		AssemblyItem(PushTag, 1),
		Instruction::JUMP
	});
}

BOOST_AUTO_TEST_CASE(cse_empty_keccak256)
{
	AssemblyItems input{
		u256(0),
		Instruction::DUP2,
		Instruction::KECCAK256
	};
	checkCSE(input, {
		u256(dev::keccak256(bytesConstRef()))
	});
}

BOOST_AUTO_TEST_CASE(cse_partial_keccak256)
{
	AssemblyItems input{
		u256(0xabcd) << (256 - 16),
		u256(0),
		Instruction::MSTORE,
		u256(2),
		u256(0),
		Instruction::KECCAK256
	};
	checkCSE(input, {
		u256(0xabcd) << (256 - 16),
		u256(0),
		Instruction::MSTORE,
		u256(dev::keccak256(bytes{0xab, 0xcd}))
	});
}

BOOST_AUTO_TEST_CASE(cse_keccak256_twice_same_location)
{
	// Keccak-256 twice from same dynamic location
	AssemblyItems input{
		Instruction::DUP2,
		Instruction::DUP1,
		Instruction::MSTORE,
		u256(64),
		Instruction::DUP2,
		Instruction::KECCAK256,
		u256(64),
		Instruction::DUP3,
		Instruction::KECCAK256
	};
	checkCSE(input, {
		Instruction::DUP2,
		Instruction::DUP1,
		Instruction::MSTORE,
		u256(64),
		Instruction::DUP2,
		Instruction::KECCAK256,
		Instruction::DUP1
	});
}

BOOST_AUTO_TEST_CASE(cse_keccak256_twice_same_content)
{
	// Keccak-256 twice from different dynamic location but with same content
	AssemblyItems input{
		Instruction::DUP1,
		u256(0x80),
		Instruction::MSTORE, // m[128] = DUP1
		u256(0x20),
		u256(0x80),
		Instruction::KECCAK256, // keccak256(m[128..(128+32)])
		Instruction::DUP2,
		u256(12),
		Instruction::MSTORE, // m[12] = DUP1
		u256(0x20),
		u256(12),
		Instruction::KECCAK256 // keccak256(m[12..(12+32)])
	};
	checkCSE(input, {
		u256(0x80),
		Instruction::DUP2,
		Instruction::DUP2,
		Instruction::MSTORE,
		u256(0x20),
		Instruction::SWAP1,
		Instruction::KECCAK256,
		u256(12),
		Instruction::DUP3,
		Instruction::SWAP1,
		Instruction::MSTORE,
		Instruction::DUP1
	});
}

BOOST_AUTO_TEST_CASE(cse_keccak256_twice_same_content_dynamic_store_in_between)
{
	// Keccak-256 twice from different dynamic location but with same content,
	// dynamic mstore in between, which forces us to re-calculate the hash
	AssemblyItems input{
		u256(0x80),
		Instruction::DUP2,
		Instruction::DUP2,
		Instruction::MSTORE, // m[128] = DUP1
		u256(0x20),
		Instruction::DUP1,
		Instruction::DUP3,
		Instruction::KECCAK256, // keccak256(m[128..(128+32)])
		u256(12),
		Instruction::DUP5,
		Instruction::DUP2,
		Instruction::MSTORE, // m[12] = DUP1
		Instruction::DUP12,
		Instruction::DUP14,
		Instruction::MSTORE, // destroys memory knowledge
		Instruction::SWAP2,
		Instruction::SWAP1,
		Instruction::SWAP2,
		Instruction::KECCAK256 // keccak256(m[12..(12+32)])
	};
	checkCSE(input, input);
}

BOOST_AUTO_TEST_CASE(cse_keccak256_twice_same_content_noninterfering_store_in_between)
{
	// Keccak-256 twice from different dynamic location but with same content,
	// dynamic mstore in between, but does not force us to re-calculate the hash
	AssemblyItems input{
		u256(0x80),
		Instruction::DUP2,
		Instruction::DUP2,
		Instruction::MSTORE, // m[128] = DUP1
		u256(0x20),
		Instruction::DUP1,
		Instruction::DUP3,
		Instruction::KECCAK256, // keccak256(m[128..(128+32)])
		u256(12),
		Instruction::DUP5,
		Instruction::DUP2,
		Instruction::MSTORE, // m[12] = DUP1
		Instruction::DUP12,
		u256(12 + 32),
		Instruction::MSTORE, // does not destoy memory knowledge
		Instruction::DUP13,
		u256(128 - 32),
		Instruction::MSTORE, // does not destoy memory knowledge
		u256(0x20),
		u256(12),
		Instruction::KECCAK256 // keccak256(m[12..(12+32)])
	};
	// if this changes too often, only count the number of SHA3 and MSTORE instructions
	AssemblyItems output = CSE(input);
	BOOST_CHECK_EQUAL(4, count(output.begin(), output.end(), AssemblyItem(Instruction::MSTORE)));
	BOOST_CHECK_EQUAL(1, count(output.begin(), output.end(), AssemblyItem(Instruction::KECCAK256)));
}

BOOST_AUTO_TEST_CASE(cse_with_initially_known_stack)
{
	eth::KnownState state = createInitialState(AssemblyItems{
		u256(0x12),
		u256(0x20),
		Instruction::ADD
	});
	AssemblyItems input{
		u256(0x12 + 0x20)
	};
	checkCSE(input, AssemblyItems{Instruction::DUP1}, state);
}

BOOST_AUTO_TEST_CASE(cse_equality_on_initially_known_stack)
{
	eth::KnownState state = createInitialState(AssemblyItems{Instruction::DUP1});
	AssemblyItems input{
		Instruction::EQ
	};
	AssemblyItems output = CSE(input, state);
	// check that it directly pushes 1 (true)
	BOOST_CHECK(find(output.begin(), output.end(), AssemblyItem(u256(1))) != output.end());
}

BOOST_AUTO_TEST_CASE(cse_access_previous_sequence)
{
	// Tests that the code generator detects whether it tries to access SLOAD instructions
	// from a sequenced expression which is not in its scope.
	eth::KnownState state = createInitialState(AssemblyItems{
		u256(0),
		Instruction::SLOAD,
		u256(1),
		Instruction::ADD,
		u256(0),
		Instruction::SSTORE
	});
	// now stored: val_1 + 1 (value at sequence 1)
	// if in the following instructions, the SLOAD cresolves to "val_1 + 1",
	// this cannot be generated because we cannot load from sequence 1 anymore.
	AssemblyItems input{
		u256(0),
		Instruction::SLOAD,
	};
	BOOST_CHECK_THROW(CSE(input, state), StackTooDeepException);
	// @todo for now, this throws an exception, but it should recover to the following
	// (or an even better version) at some point:
	// 0, SLOAD, 1, ADD, SSTORE, 0 SLOAD
}

BOOST_AUTO_TEST_CASE(cse_optimise_return)
{
	checkCSE(
		AssemblyItems{u256(0), u256(7), Instruction::RETURN},
		AssemblyItems{Instruction::STOP}
	);
}

BOOST_AUTO_TEST_CASE(control_flow_graph_remove_unused)
{
	// remove parts of the code that are unused
	AssemblyItems input{
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		u256(7),
		AssemblyItem(Tag, 1),
	};
	checkCFG(input, {});
}

BOOST_AUTO_TEST_CASE(control_flow_graph_remove_unused_loop)
{
	AssemblyItems input{
		AssemblyItem(PushTag, 3),
		Instruction::JUMP,
		AssemblyItem(Tag, 1),
		u256(7),
		AssemblyItem(PushTag, 2),
		Instruction::JUMP,
		AssemblyItem(Tag, 2),
		u256(8),
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		AssemblyItem(Tag, 3),
		u256(11)
	};
	checkCFG(input, {u256(11)});
}

BOOST_AUTO_TEST_CASE(control_flow_graph_reconnect_single_jump_source)
{
	// move code that has only one unconditional jump source
	AssemblyItems input{
		u256(1),
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		AssemblyItem(Tag, 2),
		u256(2),
		AssemblyItem(PushTag, 3),
		Instruction::JUMP,
		AssemblyItem(Tag, 1),
		u256(3),
		AssemblyItem(PushTag, 2),
		Instruction::JUMP,
		AssemblyItem(Tag, 3),
		u256(4),
	};
	checkCFG(input, {u256(1), u256(3), u256(2), u256(4)});
}

BOOST_AUTO_TEST_CASE(control_flow_graph_do_not_remove_returned_to)
{
	// do not remove parts that are "returned to"
	AssemblyItems input{
		AssemblyItem(PushTag, 1),
		AssemblyItem(PushTag, 2),
		Instruction::JUMP,
		AssemblyItem(Tag, 2),
		Instruction::JUMP,
		AssemblyItem(Tag, 1),
		u256(2)
	};
	checkCFG(input, {u256(2)});
}

BOOST_AUTO_TEST_CASE(block_deduplicator)
{
	AssemblyItems input{
		AssemblyItem(PushTag, 2),
		AssemblyItem(PushTag, 1),
		AssemblyItem(PushTag, 3),
		u256(6),
		Instruction::SWAP3,
		Instruction::JUMP,
		AssemblyItem(Tag, 1),
		u256(6),
		Instruction::SWAP3,
		Instruction::JUMP,
		AssemblyItem(Tag, 2),
		u256(6),
		Instruction::SWAP3,
		Instruction::JUMP,
		AssemblyItem(Tag, 3)
	};
	BlockDeduplicator dedup(input);
	dedup.deduplicate();

	set<u256> pushTags;
	for (AssemblyItem const& item: input)
		if (item.type() == PushTag)
			pushTags.insert(item.data());
	BOOST_CHECK_EQUAL(pushTags.size(), 2);
}

BOOST_AUTO_TEST_CASE(block_deduplicator_loops)
{
	AssemblyItems input{
		u256(0),
		Instruction::SLOAD,
		AssemblyItem(PushTag, 1),
		AssemblyItem(PushTag, 2),
		Instruction::JUMPI,
		Instruction::JUMP,
		AssemblyItem(Tag, 1),
		u256(5),
		u256(6),
		Instruction::SSTORE,
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		AssemblyItem(Tag, 2),
		u256(5),
		u256(6),
		Instruction::SSTORE,
		AssemblyItem(PushTag, 2),
		Instruction::JUMP,
	};
	BlockDeduplicator dedup(input);
	dedup.deduplicate();

	set<u256> pushTags;
	for (AssemblyItem const& item: input)
		if (item.type() == PushTag)
			pushTags.insert(item.data());
	BOOST_CHECK_EQUAL(pushTags.size(), 1);
}

BOOST_AUTO_TEST_CASE(clear_unreachable_code)
{
	AssemblyItems items{
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		u256(0),
		Instruction::SLOAD,
		AssemblyItem(Tag, 2),
		u256(5),
		u256(6),
		Instruction::SSTORE,
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		u256(5),
		u256(6)
	};
	AssemblyItems expectation{
		AssemblyItem(PushTag, 1),
		Instruction::JUMP,
		AssemblyItem(Tag, 2),
		u256(5),
		u256(6),
		Instruction::SSTORE,
		AssemblyItem(PushTag, 1),
		Instruction::JUMP
	};
	PeepholeOptimiser peepOpt(items);
	BOOST_REQUIRE(peepOpt.optimise());
	BOOST_CHECK_EQUAL_COLLECTIONS(
		items.begin(), items.end(),
		expectation.begin(), expectation.end()
	);
}

BOOST_AUTO_TEST_CASE(peephole_double_push)
{
	AssemblyItems items{
		u256(0),
		u256(0),
		u256(5),
		u256(5),
		u256(4),
		u256(5)
	};
	AssemblyItems expectation{
		u256(0),
		Instruction::DUP1,
		u256(5),
		Instruction::DUP1,
		u256(4),
		u256(5)
	};
	PeepholeOptimiser peepOpt(items);
	BOOST_REQUIRE(peepOpt.optimise());
	BOOST_CHECK_EQUAL_COLLECTIONS(
		items.begin(), items.end(),
		expectation.begin(), expectation.end()
	);
}

BOOST_AUTO_TEST_CASE(cse_sub_zero)
{
	checkCSE({
		u256(0),
		Instruction::DUP2,
		Instruction::SUB
	}, {
		Instruction::DUP1
	});

	checkCSE({
		Instruction::DUP1,
		u256(0),
		Instruction::SUB
	}, {
		u256(0),
		Instruction::DUP2,
		Instruction::SWAP1,
		Instruction::SUB
	});
}


BOOST_AUTO_TEST_SUITE_END()

}
}
} // end namespaces