path: root/test/libsolidity/SolidityOptimizer.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 <test/libsolidity/SolidityExecutionFramework.h>

#include <libevmasm/Instruction.h>

#include <boost/test/unit_test.hpp>

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

using namespace std;
using namespace dev::eth;
using namespace dev::test;

namespace dev
{
namespace solidity
{
namespace test
{

class OptimizerTestFramework: public SolidityExecutionFramework
{
public:
    OptimizerTestFramework() { }

    bytes const& compileAndRunWithOptimizer(
        std::string const& _sourceCode,
        u256 const& _value = 0,
        std::string const& _contractName = "",
        bool const _optimize = true,
        unsigned const _optimizeRuns = 200
    )
    {
        bool const c_optimize = m_optimize;
        unsigned const c_optimizeRuns = m_optimizeRuns;
        m_optimize = _optimize;
        m_optimizeRuns = _optimizeRuns;
        bytes const& ret = compileAndRun(_sourceCode, _value, _contractName);
        m_optimize = c_optimize;
        m_optimizeRuns = c_optimizeRuns;
        return ret;
    }

    /// Compiles the source code with and without optimizing.
    void compileBothVersions(
        std::string const& _sourceCode,
        u256 const& _value = 0,
        std::string const& _contractName = "",
        unsigned const _optimizeRuns = 200
    )
    {
        m_nonOptimizedBytecode = compileAndRunWithOptimizer("pragma solidity >=0.0;\n" + _sourceCode, _value, _contractName, false, _optimizeRuns);
        m_nonOptimizedContract = m_contractAddress;
        m_optimizedBytecode = compileAndRunWithOptimizer("pragma solidity >=0.0;\n" + _sourceCode, _value, _contractName, true, _optimizeRuns);
        size_t nonOptimizedSize = numInstructions(m_nonOptimizedBytecode);
        size_t optimizedSize = numInstructions(m_optimizedBytecode);
        BOOST_CHECK_MESSAGE(
            _optimizeRuns < 50 || optimizedSize < nonOptimizedSize,
            string("Optimizer did not reduce bytecode size. Non-optimized size: ") +
            to_string(nonOptimizedSize) + " - optimized size: " +
            to_string(optimizedSize)
        );
        m_optimizedContract = m_contractAddress;
    }

    template <class... Args>
    void compareVersions(std::string _sig, Args const&... _arguments)
    {
        m_contractAddress = m_nonOptimizedContract;
        bytes nonOptimizedOutput = callContractFunction(_sig, _arguments...);
        m_gasUsedNonOptimized = m_gasUsed;
        m_contractAddress = m_optimizedContract;
        bytes optimizedOutput = callContractFunction(_sig, _arguments...);
        m_gasUsedOptimized = m_gasUsed;
        BOOST_CHECK_MESSAGE(!optimizedOutput.empty(), "No optimized output for " + _sig);
        BOOST_CHECK_MESSAGE(!nonOptimizedOutput.empty(), "No un-optimized output for " + _sig);
        BOOST_CHECK_MESSAGE(nonOptimizedOutput == optimizedOutput, "Computed values do not match."
                            "\nNon-Optimized: " + toHex(nonOptimizedOutput) +
                            "\nOptimized:     " + toHex(optimizedOutput));
    }

    /// @returns the number of instructions in the given bytecode, not taking the metadata hash
    /// into account.
    size_t numInstructions(bytes const& _bytecode, boost::optional<Instruction> _which = boost::optional<Instruction>{})
    {
        BOOST_REQUIRE(_bytecode.size() > 5);
        size_t metadataSize = (_bytecode[_bytecode.size() - 2] << 8) + _bytecode[_bytecode.size() - 1];
        BOOST_REQUIRE_MESSAGE(metadataSize == 0x29, "Invalid metadata size");
        BOOST_REQUIRE(_bytecode.size() >= metadataSize + 2);
        bytes realCode = bytes(_bytecode.begin(), _bytecode.end() - metadataSize - 2);
        size_t instructions = 0;
        solidity::eachInstruction(realCode, [&](Instruction _instr, u256 const&) {
            if (!_which || *_which == _instr)
                instructions++;
        });
        return instructions;
    }

protected:
    u256 m_gasUsedOptimized;
    u256 m_gasUsedNonOptimized;
    bytes m_nonOptimizedBytecode;
    bytes m_optimizedBytecode;
    Address m_optimizedContract;
    Address m_nonOptimizedContract;
};

BOOST_FIXTURE_TEST_SUITE(SolidityOptimizer, OptimizerTestFramework)

BOOST_AUTO_TEST_CASE(smoke_test)
{
    char const* sourceCode = R"(
        contract test {
            function f(uint a) public returns (uint b) {
                return a;
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256)", u256(7));
}

BOOST_AUTO_TEST_CASE(identities)
{
    char const* sourceCode = R"(
        contract test {
            function f(int a) public returns (int b) {
                return int(0) | (int(1) * (int(0) ^ (0 + a)));
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(int256)", u256(0x12334664));
}

BOOST_AUTO_TEST_CASE(unused_expressions)
{
    char const* sourceCode = R"(
        contract test {
            uint data;
            function f() public returns (uint a, uint b) {
                10 + 20;
                data;
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f()");
}

BOOST_AUTO_TEST_CASE(constant_folding_both_sides)
{
    // if constants involving the same associative and commutative operator are applied from both
    // sides, the operator should be applied only once, because the expression compiler pushes
    // literals as late as possible
    char const* sourceCode = R"(
        contract test {
            function f(uint x) public returns (uint y) {
                return 98 ^ (7 * ((1 | (x | 1000)) * 40) ^ 102);
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256)", 7);
}

BOOST_AUTO_TEST_CASE(storage_access)
{
    char const* sourceCode = R"(
        contract test {
            uint8[40] data;
            function f(uint x) public returns (uint y) {
                data[2] = data[7] = uint8(x);
                data[4] = data[2] * 10 + data[3];
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256)", 7);
}

BOOST_AUTO_TEST_CASE(array_copy)
{
    char const* sourceCode = R"(
        contract test {
            bytes2[] data1;
            bytes5[] data2;
            function f(uint x) public returns (uint l, uint y) {
                data1.length = msg.data.length;
                for (uint i = 0; i < msg.data.length; ++i)
                    data1[i] = msg.data[i];
                data2 = data1;
                l = data2.length;
                y = uint(uint40(data2[x]));
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256)", 0);
    compareVersions("f(uint256)", 10);
    compareVersions("f(uint256)", 35);
}

BOOST_AUTO_TEST_CASE(function_calls)
{
    char const* sourceCode = R"(
        contract test {
            function f1(uint x) public returns (uint) { return x*x; }
            function f(uint x) public returns (uint) { return f1(7+x) - this.f1(x**9); }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256)", 0);
    compareVersions("f(uint256)", 10);
    compareVersions("f(uint256)", 36);
}

BOOST_AUTO_TEST_CASE(storage_write_in_loops)
{
    char const* sourceCode = R"(
        contract test {
            uint d;
            function f(uint a) public returns (uint r) {
                uint x = d;
                for (uint i = 1; i < a * a; i++) {
                    r = d;
                    d = i;
                }

            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256)", 0);
    compareVersions("f(uint256)", 10);
    compareVersions("f(uint256)", 36);
}

// Test disabled with https://github.com/ethereum/solidity/pull/762
// Information in joining branches is not retained anymore.
BOOST_AUTO_TEST_CASE(retain_information_in_branches)
{
    // This tests that the optimizer knows that we already have "z == keccak256(abi.encodePacked(y))" inside both branches.
    char const* sourceCode = R"(
        contract c {
            bytes32 d;
            uint a;
            function f(uint x, bytes32 y) public returns (uint r_a, bytes32 r_d) {
                bytes32 z = keccak256(abi.encodePacked(y));
                if (x > 8) {
                    z = keccak256(abi.encodePacked(y));
                    a = x;
                } else {
                    z = keccak256(abi.encodePacked(y));
                    a = x;
                }
                r_a = a;
                r_d = d;
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256,bytes32)", 0, "abc");
    compareVersions("f(uint256,bytes32)", 8, "def");
    compareVersions("f(uint256,bytes32)", 10, "ghi");

    bytes optimizedBytecode = compileAndRunWithOptimizer(sourceCode, 0, "c", true);
    size_t numSHA3s = 0;
    eachInstruction(optimizedBytecode, [&](Instruction _instr, u256 const&) {
        if (_instr == Instruction::KECCAK256)
            numSHA3s++;
    });
// TEST DISABLED - OPTIMIZER IS NOT EFFECTIVE ON THIS ONE ANYMORE
//  BOOST_CHECK_EQUAL(1, numSHA3s);
}

BOOST_AUTO_TEST_CASE(store_tags_as_unions)
{
    // This calls the same function from two sources and both calls have a certain Keccak-256 on
    // the stack at the same position.
    // Without storing tags as unions, the return from the shared function would not know where to
    // jump and thus all jumpdests are forced to clear their state and we do not know about the
    // sha3 anymore.
    // Note that, for now, this only works if the functions have the same number of return
    // parameters since otherwise, the return jump addresses are at different stack positions
    // which triggers the "unknown jump target" situation.
    char const* sourceCode = R"(
        contract test {
            bytes32 data;
            function f(uint x, bytes32 y) external returns (uint r_a, bytes32 r_d) {
                r_d = keccak256(abi.encodePacked(y));
                shared(y);
                r_d = keccak256(abi.encodePacked(y));
                r_a = 5;
            }
            function g(uint x, bytes32 y) external returns (uint r_a, bytes32 r_d) {
                r_d = keccak256(abi.encodePacked(y));
                shared(y);
                r_d = bytes32(uint(keccak256(abi.encodePacked(y))) + 2);
                r_a = 7;
            }
            function shared(bytes32 y) internal {
                data = keccak256(abi.encodePacked(y));
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(uint256,bytes32)", 7, "abc");

    bytes optimizedBytecode = compileAndRunWithOptimizer(sourceCode, 0, "test", true);
    size_t numSHA3s = 0;
    eachInstruction(optimizedBytecode, [&](Instruction _instr, u256 const&) {
        if (_instr == Instruction::KECCAK256)
            numSHA3s++;
    });
// TEST DISABLED UNTIL 93693404 IS IMPLEMENTED
//  BOOST_CHECK_EQUAL(2, numSHA3s);
}

BOOST_AUTO_TEST_CASE(incorrect_storage_access_bug)
{
    // This bug appeared because a Keccak-256 operation with too low sequence number was used,
    // resulting in memory not being rewritten before the Keccak-256. The fix was to
    // take the max of the min sequence numbers when merging the states.
    char const* sourceCode = R"(
        contract C
        {
            mapping(uint => uint) data;
            function f() public returns (uint)
            {
                if(data[now] == 0)
                    data[uint(-7)] = 5;
                return data[now];
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f()");
}

BOOST_AUTO_TEST_CASE(sequence_number_for_calls)
{
    // This is a test for a bug that was present because we did not increment the sequence
    // number for CALLs - CALLs can read and write from memory (and DELEGATECALLs can do the same
    // to storage), so the sequence number should be incremented.
    char const* sourceCode = R"(
        contract test {
            function f(string memory a, string memory b) public returns (bool) { return sha256(bytes(a)) == sha256(bytes(b)); }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f(string,string)", 0x40, 0x80, 3, "abc", 3, "def");
}

BOOST_AUTO_TEST_CASE(computing_constants)
{
    char const* sourceCode = R"(
        contract C {
            uint m_a;
            uint m_b;
            uint m_c;
            uint m_d;
            constructor() public {
                set();
            }
            function set() public returns (uint) {
                m_a = 0x77abc0000000000000000000000000000000000000000000000000000000001;
                m_b = 0x817416927846239487123469187231298734162934871263941234127518276;
                g();
                return 1;
            }
            function g() public {
                m_b = 0x817416927846239487123469187231298734162934871263941234127518276;
                m_c = 0x817416927846239487123469187231298734162934871263941234127518276;
                h();
            }
            function h() public {
                m_d = 0xff05694900000000000000000000000000000000000000000000000000000000;
            }
            function get() public returns (uint ra, uint rb, uint rc, uint rd) {
                ra = m_a;
                rb = m_b;
                rc = m_c;
                rd = m_d;
            }
        }
    )";
    compileBothVersions(sourceCode, 0, "C", 1);
    compareVersions("get()");
    compareVersions("set()");
    compareVersions("get()");

    bytes optimizedBytecode = compileAndRunWithOptimizer(sourceCode, 0, "C", true, 1);
    bytes complicatedConstant = toBigEndian(u256("0x817416927846239487123469187231298734162934871263941234127518276"));
    unsigned occurrences = 0;
    for (auto iter = optimizedBytecode.cbegin(); iter < optimizedBytecode.cend(); ++occurrences)
    {
        iter = search(iter, optimizedBytecode.cend(), complicatedConstant.cbegin(), complicatedConstant.cend());
        if (iter < optimizedBytecode.cend())
            ++iter;
    }
    BOOST_CHECK_EQUAL(2, occurrences);

    bytes constantWithZeros = toBigEndian(u256("0x77abc0000000000000000000000000000000000000000000000000000000001"));
    BOOST_CHECK(search(
        optimizedBytecode.cbegin(),
        optimizedBytecode.cend(),
        constantWithZeros.cbegin(),
        constantWithZeros.cend()
    ) == optimizedBytecode.cend());
}


BOOST_AUTO_TEST_CASE(constant_optimization_early_exit)
{
    // This tests that the constant optimizer does not try to find the best representation
    // indefinitely but instead stops after some number of iterations.
    char const* sourceCode = R"(
    contract HexEncoding {
        function hexEncodeTest(address addr) public returns (bytes32 ret) {
            uint x = uint(addr) / 2**32;

            // Nibble interleave
            x = x & 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff;
            x = (x | (x * 2**64)) & 0x0000000000000000ffffffffffffffff0000000000000000ffffffffffffffff;
            x = (x | (x * 2**32)) & 0x00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff;
            x = (x | (x * 2**16)) & 0x0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff;
            x = (x | (x * 2** 8)) & 0x00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff;
            x = (x | (x * 2** 4)) & 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f;

            // Hex encode
            uint h = (x & 0x0808080808080808080808080808080808080808080808080808080808080808) / 8;
            uint i = (x & 0x0404040404040404040404040404040404040404040404040404040404040404) / 4;
            uint j = (x & 0x0202020202020202020202020202020202020202020202020202020202020202) / 2;
            x = x + (h & (i | j)) * 0x27 + 0x3030303030303030303030303030303030303030303030303030303030303030;

            // Store and load next batch
            assembly {
                mstore(0, x)
            }
            x = uint(addr) * 2**96;

            // Nibble interleave
            x = x & 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff;
            x = (x | (x * 2**64)) & 0x0000000000000000ffffffffffffffff0000000000000000ffffffffffffffff;
            x = (x | (x * 2**32)) & 0x00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff;
            x = (x | (x * 2**16)) & 0x0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff;
            x = (x | (x * 2** 8)) & 0x00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff;
            x = (x | (x * 2** 4)) & 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f;

            // Hex encode
            h = (x & 0x0808080808080808080808080808080808080808080808080808080808080808) / 8;
            i = (x & 0x0404040404040404040404040404040404040404040404040404040404040404) / 4;
            j = (x & 0x0202020202020202020202020202020202020202020202020202020202020202) / 2;
            x = x + (h & (i | j)) * 0x27 + 0x3030303030303030303030303030303030303030303030303030303030303030;

            // Store and hash
            assembly {
                mstore(32, x)
                ret := keccak256(0, 40)
            }
        }
    }
    )";
    auto start = std::chrono::steady_clock::now();
    compileBothVersions(sourceCode);
    double duration = std::chrono::duration<double>(std::chrono::steady_clock::now() - start).count();
    BOOST_CHECK_MESSAGE(duration < 20, "Compilation of constants took longer than 20 seconds.");
    compareVersions("hexEncodeTest(address)", u256(0x123456789));
}

BOOST_AUTO_TEST_CASE(inconsistency)
{
    // This is a test of a bug in the optimizer.
    char const* sourceCode = R"(
        contract Inconsistency {
            struct Value {
                uint badnum;
                uint number;
            }

            struct Container {
                uint[] valueIndices;
                Value[] values;
            }

            Container[] containers;
            uint[] valueIndices;
            uint INDEX_ZERO = 0;
            uint  debug;

            // Called with params: containerIndex=0, valueIndex=0
            function levelIII(uint containerIndex, uint valueIndex) private {
                Container storage container = containers[containerIndex];
                Value storage value = container.values[valueIndex];
                debug = container.valueIndices[value.number];
            }
            function levelII() private {
                for (uint i = 0; i < valueIndices.length; i++) {
                    levelIII(INDEX_ZERO, valueIndices[i]);
                }
            }

            function trigger() public returns (uint) {
                containers.length++;
                Container storage container = containers[0];

                container.values.push(Value({
                    badnum: 9000,
                    number: 0
                }));

                container.valueIndices.length++;
                valueIndices.length++;

                levelII();
                return debug;
            }

            function DoNotCallButDoNotDelete() public {
                levelII();
                levelIII(1, 2);
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("trigger()");
}

BOOST_AUTO_TEST_CASE(dead_code_elimination_across_assemblies)
{
    // This tests that a runtime-function that is stored in storage in the constructor
    // is not removed as part of dead code elimination.
    char const* sourceCode = R"(
        contract DCE {
            function () internal returns (uint) stored;
            constructor() public {
                stored = f;
            }
            function f() internal returns (uint) { return 7; }
            function test() public returns (uint) { return stored(); }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("test()");
}

BOOST_AUTO_TEST_CASE(invalid_state_at_control_flow_join)
{
    char const* sourceCode = R"(
        contract Test {
            uint256 public totalSupply = 100;
            function f() public returns (uint r) {
                if (false)
                    r = totalSupply;
                totalSupply -= 10;
            }
            function test() public returns (uint) {
                f();
                return this.totalSupply();
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("test()");
}

BOOST_AUTO_TEST_CASE(init_empty_dynamic_arrays)
{
    // This is not so much an optimizer test, but rather a test
    // that allocating empty arrays is implemented efficiently.
    // In particular, initializing a dynamic memory array does
    // not use any memory.
    char const* sourceCode = R"(
        contract Test {
            function f() public pure returns (uint r) {
                uint[][] memory x = new uint[][](20000);
                return x.length;
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f()");
    BOOST_CHECK_LE(m_gasUsedNonOptimized, 1900000);
    BOOST_CHECK_LE(1600000, m_gasUsedNonOptimized);
}

BOOST_AUTO_TEST_CASE(optimise_multi_stores)
{
    char const* sourceCode = R"(
        contract Test {
            struct S { uint16 a; uint16 b; uint16[3] c; uint[] dyn; }
            uint padding;
            S[] s;
            function f() public returns (uint16, uint16, uint16[3] memory, uint) {
                uint16[3] memory c;
                c[0] = 7;
                c[1] = 8;
                c[2] = 9;
                s.push(S(1, 2, c, new uint[](4)));
                return (s[0].a, s[0].b, s[0].c, s[0].dyn[2]);
            }
        }
    )";
    compileBothVersions(sourceCode);
    compareVersions("f()");
    BOOST_CHECK_EQUAL(numInstructions(m_nonOptimizedBytecode, Instruction::SSTORE), 9);
    BOOST_CHECK_EQUAL(numInstructions(m_optimizedBytecode, Instruction::SSTORE), 8);
}

BOOST_AUTO_TEST_SUITE_END()

}
}
} // end namespaces