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https://github.com/ethereum/solidity
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Merge pull request #4068 from ethereum/gasEstimatorPerformance
Gas estimator performance
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commit
c79351efb0
@ -3,6 +3,7 @@
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Features:
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* Build System: Update internal dependency of jsoncpp to 1.8.4, which introduces more strictness and reduces memory usage.
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* Code Generator: Use native shift instructions on target Constantinople.
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* Gas Estimator: Only explore paths with higher gas costs. This reduces accuracy but greatly improves the speed of gas estimation.
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* Optimizer: Remove unnecessary masking of the result of known short instructions (``ADDRESS``, ``CALLER``, ``ORIGIN`` and ``COINBASE``).
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* Type Checker: Deprecate the ``years`` unit denomination and raise a warning for it (or an error as experimental 0.5.0 feature).
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* Type Checker: Make literals (without explicit type casting) an error for tight packing as experimental 0.5.0 feature.
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@ -43,7 +43,7 @@ GasMeter::GasConsumption PathGasMeter::estimateMax(
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auto path = unique_ptr<GasPath>(new GasPath());
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path->index = _startIndex;
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path->state = _state->copy();
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m_queue.push_back(move(path));
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queue(move(path));
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GasMeter::GasConsumption gas;
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while (!m_queue.empty() && !gas.isInfinite)
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@ -51,12 +51,23 @@ GasMeter::GasConsumption PathGasMeter::estimateMax(
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return gas;
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}
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void PathGasMeter::queue(std::unique_ptr<GasPath>&& _newPath)
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{
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if (
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m_highestGasUsagePerJumpdest.count(_newPath->index) &&
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_newPath->gas < m_highestGasUsagePerJumpdest.at(_newPath->index)
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)
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return;
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m_highestGasUsagePerJumpdest[_newPath->index] = _newPath->gas;
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m_queue[_newPath->index] = move(_newPath);
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}
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GasMeter::GasConsumption PathGasMeter::handleQueueItem()
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{
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assertThrow(!m_queue.empty(), OptimizerException, "");
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unique_ptr<GasPath> path = move(m_queue.back());
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m_queue.pop_back();
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unique_ptr<GasPath> path = move(m_queue.rbegin()->second);
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m_queue.erase(--m_queue.end());
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shared_ptr<KnownState> state = path->state;
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GasMeter meter(state, m_evmVersion, path->largestMemoryAccess);
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@ -117,7 +128,7 @@ GasMeter::GasConsumption PathGasMeter::handleQueueItem()
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newPath->largestMemoryAccess = meter.largestMemoryAccess();
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newPath->state = state->copy();
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newPath->visitedJumpdests = path->visitedJumpdests;
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m_queue.push_back(move(newPath));
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queue(move(newPath));
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}
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if (branchStops)
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@ -58,9 +58,17 @@ public:
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GasMeter::GasConsumption estimateMax(size_t _startIndex, std::shared_ptr<KnownState> const& _state);
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private:
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/// Adds a new path item to the queue, but only if we do not already have
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/// a higher gas usage at that point.
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/// This is not exact as different state might influence higher gas costs at a later
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/// point in time, but it greatly reduces computational overhead.
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void queue(std::unique_ptr<GasPath>&& _newPath);
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GasMeter::GasConsumption handleQueueItem();
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std::vector<std::unique_ptr<GasPath>> m_queue;
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/// Map of jumpdest -> gas path, so not really a queue. We only have one queued up
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/// item per jumpdest, because of the behaviour of `queue` above.
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std::map<size_t, std::unique_ptr<GasPath>> m_queue;
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std::map<size_t, GasMeter::GasConsumption> m_highestGasUsagePerJumpdest;
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std::map<u256, size_t> m_tagPositions;
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AssemblyItems const& m_items;
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solidity::EVMVersion m_evmVersion;
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@ -307,6 +307,46 @@ BOOST_AUTO_TEST_CASE(regular_functions_exclude_fallback)
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testCreationTimeGas(sourceCode);
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testRunTimeGas("x()", vector<bytes>{encodeArgs()});
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}
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BOOST_AUTO_TEST_CASE(complex_control_flow)
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{
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// This crashed the gas estimator previously (or took a very long time).
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// Now we do not follow branches if they start out with lower gas costs than the ones
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// we previously considered. This of course reduces accuracy.
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char const* sourceCode = R"(
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contract log {
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function ln(int128 x) constant returns (int128 result) {
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int128 t = x / 256;
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int128 y = 5545177;
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x = t;
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t = x * 16; if (t <= 1000000) { x = t; y = y - 2772588; }
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t = x * 4; if (t <= 1000000) { x = t; y = y - 1386294; }
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t = x * 2; if (t <= 1000000) { x = t; y = y - 693147; }
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t = x + x / 2; if (t <= 1000000) { x = t; y = y - 405465; }
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t = x + x / 4; if (t <= 1000000) { x = t; y = y - 223144; }
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t = x + x / 8; if (t <= 1000000) { x = t; y = y - 117783; }
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t = x + x / 16; if (t <= 1000000) { x = t; y = y - 60624; }
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t = x + x / 32; if (t <= 1000000) { x = t; y = y - 30771; }
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t = x + x / 64; if (t <= 1000000) { x = t; y = y - 15504; }
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t = x + x / 128; if (t <= 1000000) { x = t; y = y - 7782; }
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t = x + x / 256; if (t <= 1000000) { x = t; y = y - 3898; }
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t = x + x / 512; if (t <= 1000000) { x = t; y = y - 1951; }
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t = x + x / 1024; if (t <= 1000000) { x = t; y = y - 976; }
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t = x + x / 2048; if (t <= 1000000) { x = t; y = y - 488; }
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t = x + x / 4096; if (t <= 1000000) { x = t; y = y - 244; }
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t = x + x / 8192; if (t <= 1000000) { x = t; y = y - 122; }
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t = x + x / 16384; if (t <= 1000000) { x = t; y = y - 61; }
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t = x + x / 32768; if (t <= 1000000) { x = t; y = y - 31; }
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t = x + x / 65536; if (t <= 1000000) { y = y - 15; }
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return y;
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}
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}
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)";
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testCreationTimeGas(sourceCode);
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// max gas is used for small x
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testRunTimeGas("ln(int128)", vector<bytes>{encodeArgs(0), encodeArgs(10), encodeArgs(105), encodeArgs(30000)});
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}
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BOOST_AUTO_TEST_SUITE_END()
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}
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