From 02ea0e547f3faa687f9c986ca9a0201b995846c0 Mon Sep 17 00:00:00 2001 From: Alex Beregszaszi Date: Wed, 4 Apr 2018 15:28:15 +0200 Subject: Replace comparison operators with opposites if preceded by SWAP1 --- Changelog.md | 1 + libevmasm/PeepholeOptimiser.cpp | 28 ++++++++++++++++++++++++++- test/libevmasm/Optimiser.cpp | 43 ++++++++++++++++++++++++++++++++++++----- 3 files changed, 66 insertions(+), 6 deletions(-) diff --git a/Changelog.md b/Changelog.md index 9618dfa7..1d854291 100644 --- a/Changelog.md +++ b/Changelog.md @@ -6,6 +6,7 @@ Features: * General: Support accessing dynamic return data in post-byzantium EVMs. * Interfaces: Allow overriding external functions in interfaces with public in an implementing contract. * Optimizer: Remove useless ``SWAP1`` instruction preceding a commutative instruction (such as ``ADD``, ``MUL``, etc). + * Optimizer: Replace comparison operators (``LT``, ``GT``, etc) with opposites if preceded by ``SWAP1``, e.g. ``SWAP1 LT`` is replaced with ``GT``. * Optimizer: Optimize across ``mload`` if ``msize()`` is not used. * Syntax Checker: Issue warning for empty structs (or error as experimental 0.5.0 feature). * General: Introduce new constructor syntax using the ``constructor`` keyword as experimental 0.5.0 feature. diff --git a/libevmasm/PeepholeOptimiser.cpp b/libevmasm/PeepholeOptimiser.cpp index 30646545..8a39de24 100644 --- a/libevmasm/PeepholeOptimiser.cpp +++ b/libevmasm/PeepholeOptimiser.cpp @@ -173,6 +173,32 @@ struct CommutativeSwap: SimplePeepholeOptimizerMethod } }; +struct SwapComparison: SimplePeepholeOptimizerMethod +{ + static bool applySimple(AssemblyItem const& _swap, AssemblyItem const& _op, std::back_insert_iterator _out) + { + map swappableOps{ + { Instruction::LT, Instruction::GT }, + { Instruction::GT, Instruction::LT }, + { Instruction::SLT, Instruction::SGT }, + { Instruction::SGT, Instruction::SLT } + }; + + if ( + _swap.type() == Operation && + _swap.instruction() == Instruction::SWAP1 && + _op.type() == Operation && + swappableOps.count(_op.instruction()) + ) + { + *_out = swappableOps.at(_op.instruction()); + return true; + } + else + return false; + } +}; + struct JumpToNext: SimplePeepholeOptimizerMethod { static size_t applySimple( @@ -279,7 +305,7 @@ bool PeepholeOptimiser::optimise() { OptimiserState state {m_items, 0, std::back_inserter(m_optimisedItems)}; while (state.i < m_items.size()) - applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity()); + applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), SwapComparison(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity()); if (m_optimisedItems.size() < m_items.size() || ( m_optimisedItems.size() == m_items.size() && ( eth::bytesRequired(m_optimisedItems, 3) < eth::bytesRequired(m_items, 3) || diff --git a/test/libevmasm/Optimiser.cpp b/test/libevmasm/Optimiser.cpp index b622b4fb..089be45d 100644 --- a/test/libevmasm/Optimiser.cpp +++ b/test/libevmasm/Optimiser.cpp @@ -888,7 +888,7 @@ BOOST_AUTO_TEST_CASE(peephole_commutative_swap1) PeepholeOptimiser peepOpt(items); BOOST_REQUIRE(peepOpt.optimise()); BOOST_CHECK_EQUAL_COLLECTIONS( - items.begin(), items.end(), + items.begin(), items.end(), expectation.begin(), expectation.end() ); } @@ -903,9 +903,7 @@ BOOST_AUTO_TEST_CASE(peephole_noncommutative_swap1) Instruction::SDIV, Instruction::MOD, Instruction::SMOD, - Instruction::EXP, - Instruction::LT, - Instruction::GT + Instruction::EXP }; for (Instruction const op: ops) { @@ -928,7 +926,42 @@ BOOST_AUTO_TEST_CASE(peephole_noncommutative_swap1) PeepholeOptimiser peepOpt(items); BOOST_REQUIRE(!peepOpt.optimise()); BOOST_CHECK_EQUAL_COLLECTIONS( - items.begin(), items.end(), + items.begin(), items.end(), + expectation.begin(), expectation.end() + ); + } +} + +BOOST_AUTO_TEST_CASE(peephole_swap_comparison) +{ + map swappableOps{ + { Instruction::LT, Instruction::GT }, + { Instruction::GT, Instruction::LT }, + { Instruction::SLT, Instruction::SGT }, + { Instruction::SGT, Instruction::SLT } + }; + + for (auto const& op: swappableOps) + { + AssemblyItems items{ + u256(1), + u256(2), + Instruction::SWAP1, + op.first, + u256(4), + u256(5) + }; + AssemblyItems expectation{ + u256(1), + u256(2), + op.second, + u256(4), + u256(5) + }; + PeepholeOptimiser peepOpt(items); + BOOST_REQUIRE(peepOpt.optimise()); + BOOST_CHECK_EQUAL_COLLECTIONS( + items.begin(), items.end(), expectation.begin(), expectation.end() ); } -- cgit v1.2.3 From 8dc9113e370a2edd42213c2c0cca811a3dbd8dd4 Mon Sep 17 00:00:00 2001 From: Alex Beregszaszi Date: Thu, 5 Apr 2018 10:41:43 +0200 Subject: Add end-to-end test for SwapComparison and CommutativeSwap peephole optimisers --- test/libsolidity/SolidityEndToEndTest.cpp | 44 +++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp index b58ebee4..4b4fc2af 100644 --- a/test/libsolidity/SolidityEndToEndTest.cpp +++ b/test/libsolidity/SolidityEndToEndTest.cpp @@ -11032,6 +11032,50 @@ BOOST_AUTO_TEST_CASE(staticcall_for_view_and_pure) } } +BOOST_AUTO_TEST_CASE(swap_peephole_optimisation) +{ + char const* sourceCode = R"( + contract C { + function lt(uint a, uint b) returns (bool c) { + assembly { + a + b + swap1 + lt + =: c + } + } + function add(uint a, uint b) returns (uint c) { + assembly { + a + b + swap1 + add + =: c + } + } + function div(uint a, uint b) returns (uint c) { + assembly { + a + b + swap1 + div + =: c + } + } + } + )"; + compileAndRun(sourceCode); + BOOST_CHECK(callContractFunction("lt(uint256,uint256)", u256(1), u256(2)) == encodeArgs(u256(1))); + BOOST_CHECK(callContractFunction("lt(uint256,uint256)", u256(2), u256(1)) == encodeArgs(u256(0))); + BOOST_CHECK(callContractFunction("add(uint256,uint256)", u256(1), u256(2)) == encodeArgs(u256(3))); + BOOST_CHECK(callContractFunction("add(uint256,uint256)", u256(100), u256(200)) == encodeArgs(u256(300))); + BOOST_CHECK(callContractFunction("div(uint256,uint256)", u256(2), u256(1)) == encodeArgs(u256(2))); + BOOST_CHECK(callContractFunction("div(uint256,uint256)", u256(200), u256(10)) == encodeArgs(u256(20))); + BOOST_CHECK(callContractFunction("div(uint256,uint256)", u256(1), u256(0)) == encodeArgs(u256(0))); + BOOST_CHECK(callContractFunction("div(uint256,uint256)", u256(0), u256(1)) == encodeArgs(u256(0))); +} + BOOST_AUTO_TEST_SUITE_END() } -- cgit v1.2.3