From 965f005a989e0b7fb5a46f364bfb96dad2e18aae Mon Sep 17 00:00:00 2001 From: chriseth Date: Tue, 24 Mar 2015 14:53:15 +0100 Subject: [PATCH] Storage access optimisation. --- libevmcore/CommonSubexpressionEliminator.cpp | 205 ++++++++++++++----- libevmcore/CommonSubexpressionEliminator.h | 67 +++++- libevmcore/ExpressionClasses.cpp | 70 +++++-- libevmcore/ExpressionClasses.h | 10 +- test/SolidityOptimizer.cpp | 180 ++++++++++++++++ 5 files changed, 453 insertions(+), 79 deletions(-) diff --git a/libevmcore/CommonSubexpressionEliminator.cpp b/libevmcore/CommonSubexpressionEliminator.cpp index 7fed03b4e..43d01fc85 100644 --- a/libevmcore/CommonSubexpressionEliminator.cpp +++ b/libevmcore/CommonSubexpressionEliminator.cpp @@ -45,19 +45,24 @@ vector CommonSubexpressionEliminator::getOptimizedItems() // Debug info: //stream(cout, initialStackContents, targetStackContents); - return CSECodeGenerator(m_expressionClasses).generateCode(initialStackContents, targetStackContents); + return CSECodeGenerator(m_expressionClasses, m_storageWrites).generateCode( + initialStackContents, + targetStackContents + ); } ostream& CommonSubexpressionEliminator::stream( ostream& _out, - map _currentStack, + map _initialStack, map _targetStack ) const { auto streamExpressionClass = [this](ostream& _out, ExpressionClasses::Id _id) { auto const& expr = m_expressionClasses.representative(_id); - _out << " " << _id << ": " << *expr.item; + _out << " " << dec << _id << ": " << *expr.item; + if (expr.sequenceNumber) + _out << "@" << dec << expr.sequenceNumber; _out << "("; for (ExpressionClasses::Id arg: expr.arguments) _out << dec << arg << ","; @@ -66,18 +71,12 @@ ostream& CommonSubexpressionEliminator::stream( _out << "Optimizer analysis:" << endl; _out << "Final stack height: " << dec << m_stackHeight << endl; - _out << "Stack elements: " << endl; - for (auto const& it: m_stackElements) - { - _out << " " << dec << it.first << " = "; - streamExpressionClass(_out, it.second); - } _out << "Equivalence classes: " << endl; for (ExpressionClasses::Id eqClass = 0; eqClass < m_expressionClasses.size(); ++eqClass) streamExpressionClass(_out, eqClass); - _out << "Current stack: " << endl; - for (auto const& it: _currentStack) + _out << "Initial stack: " << endl; + for (auto const& it: _initialStack) { _out << " " << dec << it.first << ": "; streamExpressionClass(_out, it.second); @@ -96,9 +95,8 @@ void CommonSubexpressionEliminator::feedItem(AssemblyItem const& _item) { if (_item.type() != Operation) { - if (_item.deposit() != 1) - BOOST_THROW_EXCEPTION(InvalidDeposit()); - setStackElement(++m_stackHeight, m_expressionClasses.find(_item, {})); + assertThrow(_item.deposit() == 1, InvalidDeposit, ""); + setStackElement(++m_stackHeight, m_expressionClasses.find(_item, {}, false)); } else { @@ -119,7 +117,12 @@ void CommonSubexpressionEliminator::feedItem(AssemblyItem const& _item) vector arguments(info.args); for (int i = 0; i < info.args; ++i) arguments[i] = stackElement(m_stackHeight - i); - setStackElement(m_stackHeight + _item.deposit(), m_expressionClasses.find(_item, arguments)); + if (_item.instruction() == Instruction::SSTORE) + storeInStorage(arguments[0], arguments[1]); + else if (_item.instruction() == Instruction::SLOAD) + setStackElement(m_stackHeight + _item.deposit(), loadFromStorage(arguments[0])); + else + setStackElement(m_stackHeight + _item.deposit(), m_expressionClasses.find(_item, arguments, false)); } m_stackHeight += _item.deposit(); } @@ -132,8 +135,7 @@ void CommonSubexpressionEliminator::setStackElement(int _stackHeight, Expression void CommonSubexpressionEliminator::swapStackElements(int _stackHeightA, int _stackHeightB) { - if (_stackHeightA == _stackHeightB) - BOOST_THROW_EXCEPTION(OptimizerException() << errinfo_comment("Swap on same stack elements.")); + assertThrow(_stackHeightA != _stackHeightB, OptimizerException, "Swap on same stack elements."); // ensure they are created stackElement(_stackHeightA); stackElement(_stackHeightB); @@ -157,6 +159,33 @@ ExpressionClasses::Id CommonSubexpressionEliminator::initialStackElement(int _st return m_expressionClasses.find(AssemblyItem(dupInstruction(1 - _stackHeight))); } +void CommonSubexpressionEliminator::storeInStorage(ExpressionClasses::Id _slot, ExpressionClasses::Id _value) +{ + if (m_storageContent.count(_slot) && m_storageContent[_slot] == _value) + // do not execute the storage if we know that the value is already there + return; + m_sequenceNumber ++; + decltype(m_storageContent) storageContents; + // copy over values at points where we know that they are different from _slot + for (auto const& storageItem: m_storageContent) + if (m_expressionClasses.knownToBeDifferent(storageItem.first, _slot)) + storageContents.insert(storageItem); + m_storageContent = move(storageContents); + ExpressionClasses::Id id = m_expressionClasses.find(Instruction::SSTORE, {_slot, _value}, true, m_sequenceNumber); + m_storageWrites.insert(StorageWriteOperation(_slot, m_sequenceNumber, id)); + m_storageContent[_slot] = _value; + // increment a second time so that we get unique sequence numbers for writes + m_sequenceNumber ++; +} + +ExpressionClasses::Id CommonSubexpressionEliminator::loadFromStorage(ExpressionClasses::Id _slot) +{ + if (m_storageContent.count(_slot)) + return m_storageContent.at(_slot); + else + return m_storageContent[_slot] = m_expressionClasses.find(Instruction::SLOAD, {_slot}, true, m_sequenceNumber); +} + bool SemanticInformation::breaksBasicBlock(AssemblyItem const& _item) { switch (_item.type()) @@ -180,6 +209,8 @@ bool SemanticInformation::breaksBasicBlock(AssemblyItem const& _item) if (_item.instruction() == Instruction::GAS || _item.instruction() == Instruction::PC) return true; // GAS and PC assume a specific order of opcodes InstructionInfo info = instructionInfo(_item.instruction()); + if (_item.instruction() == Instruction::SSTORE) + return false; // the second requirement will be lifted once it is implemented return info.sideEffects || info.args > 2; } @@ -230,26 +261,49 @@ AssemblyItems CSECodeGenerator::generateCode( // @todo: provide information about the positions of copies of class elements - // generate the dependency graph + // generate the dependency graph starting from final storage writes and target stack contents + for (auto it = m_storageWrites.begin(); it != m_storageWrites.end();) + { + auto next = it; + ++next; + if (next == m_storageWrites.end() || next->slot != it->slot) + // last write to that storage slot + addDependencies(it->expression); + it = next; + } for (auto const& targetItem: _targetStackContents) { m_finalClasses.insert(targetItem.second); addDependencies(targetItem.second); } - // generate the actual elements + // Perform all operations on storage in order, if they are needed. + //@todo use better data structures to optimize these loops + unsigned maxSequenceNumber = 1; + for (StorageWriteOperation const& op: m_storageWrites) + maxSequenceNumber = max(maxSequenceNumber, op.sequenceNumber + 1); + for (unsigned sequenceNumber = 1; sequenceNumber <= maxSequenceNumber; ++sequenceNumber) + for (auto const& depPair: m_neededBy) + for (ExpressionClasses::Id const& id: {depPair.first, depPair.second}) + if ( + m_expressionClasses.representative(id).sequenceNumber == sequenceNumber && + !m_classPositions.count(id) + ) + generateClassElement(id, true); + + // generate the target stack elements for (auto const& targetItem: _targetStackContents) { - removeStackTopIfPossible(); int position = generateClassElement(targetItem.second); + assertThrow(position != c_invalidPosition, OptimizerException, ""); if (position == targetItem.first) continue; if (position < targetItem.first) // it is already at its target, we need another copy appendDup(position); else - appendSwapOrRemove(position); - appendSwapOrRemove(targetItem.first); + appendOrRemoveSwap(position); + appendOrRemoveSwap(targetItem.first); } // remove surplus elements @@ -270,23 +324,48 @@ AssemblyItems CSECodeGenerator::generateCode( // neither initial no target stack, no change in height finalHeight = 0; assertThrow(finalHeight == m_stackHeight, OptimizerException, "Incorrect final stack height."); - return m_generatedItems; } void CSECodeGenerator::addDependencies(ExpressionClasses::Id _c) { if (m_neededBy.count(_c)) - return; - for (ExpressionClasses::Id argument: m_expressionClasses.representative(_c).arguments) + return; // we already computed the dependencies for _c + ExpressionClasses::Expression const& expr = m_expressionClasses.representative(_c); + for (ExpressionClasses::Id argument: expr.arguments) { addDependencies(argument); m_neededBy.insert(make_pair(argument, _c)); } + if (expr.item->type() == Operation && expr.item->instruction() == Instruction::SLOAD) + { + // this loads an unknown value from storage and thus, in addition to its arguments, depends + // on all SSTORE operations to addresses where we do not know that they are different that + // occur before this SLOAD + ExpressionClasses::Id slotToLoadFrom = expr.arguments.at(0); + for (auto it = m_storageWrites.begin(); it != m_storageWrites.end();) + { + auto next = it; + ++next; + // note that SSTORE and SLOAD never have the same sequence number + if (it->sequenceNumber < expr.sequenceNumber && + !m_expressionClasses.knownToBeDifferent(it->slot, slotToLoadFrom) && + (next == m_storageWrites.end() || next->sequenceNumber > expr.sequenceNumber) + ) + { + addDependencies(it->expression); + m_neededBy.insert(make_pair(it->expression, _c)); + } + it = next; + } + } } -int CSECodeGenerator::generateClassElement(ExpressionClasses::Id _c) +int CSECodeGenerator::generateClassElement(ExpressionClasses::Id _c, bool _allowSequenced) { + // do some cleanup + removeStackTopIfPossible(); + if (m_classPositions.count(_c)) { assertThrow( @@ -296,7 +375,13 @@ int CSECodeGenerator::generateClassElement(ExpressionClasses::Id _c) ); return m_classPositions[_c]; } - ExpressionClasses::Ids const& arguments = m_expressionClasses.representative(_c).arguments; + ExpressionClasses::Expression const& expr = m_expressionClasses.representative(_c); + assertThrow( + _allowSequenced || expr.sequenceNumber == 0, + OptimizerException, + "Sequence constrained operation requested out of sequence." + ); + ExpressionClasses::Ids const& arguments = expr.arguments; for (ExpressionClasses::Id arg: boost::adaptors::reverse(arguments)) generateClassElement(arg); @@ -307,42 +392,42 @@ int CSECodeGenerator::generateClassElement(ExpressionClasses::Id _c) if (arguments.size() == 1) { if (canBeRemoved(arguments[0], _c)) - appendSwapOrRemove(generateClassElement(arguments[0])); + appendOrRemoveSwap(classElementPosition(arguments[0])); else - appendDup(generateClassElement(arguments[0])); + appendDup(classElementPosition(arguments[0])); } else if (arguments.size() == 2) { if (canBeRemoved(arguments[1], _c)) { - appendSwapOrRemove(generateClassElement(arguments[1])); + appendOrRemoveSwap(classElementPosition(arguments[1])); if (arguments[0] == arguments[1]) appendDup(m_stackHeight); else if (canBeRemoved(arguments[0], _c)) { - appendSwapOrRemove(m_stackHeight - 1); - appendSwapOrRemove(generateClassElement(arguments[0])); + appendOrRemoveSwap(m_stackHeight - 1); + appendOrRemoveSwap(classElementPosition(arguments[0])); } else - appendDup(generateClassElement(arguments[0])); + appendDup(classElementPosition(arguments[0])); } else { if (arguments[0] == arguments[1]) { - appendDup(generateClassElement(arguments[0])); + appendDup(classElementPosition(arguments[0])); appendDup(m_stackHeight); } else if (canBeRemoved(arguments[0], _c)) { - appendSwapOrRemove(generateClassElement(arguments[0])); - appendDup(generateClassElement(arguments[1])); - appendSwapOrRemove(m_stackHeight - 1); + appendOrRemoveSwap(classElementPosition(arguments[0])); + appendDup(classElementPosition(arguments[1])); + appendOrRemoveSwap(m_stackHeight - 1); } else { - appendDup(generateClassElement(arguments[1])); - appendDup(generateClassElement(arguments[0])); + appendDup(classElementPosition(arguments[1])); + appendDup(classElementPosition(arguments[0])); } } } @@ -355,20 +440,41 @@ int CSECodeGenerator::generateClassElement(ExpressionClasses::Id _c) for (size_t i = 0; i < arguments.size(); ++i) assertThrow(m_stack[m_stackHeight - i] == arguments[i], OptimizerException, "Expected arguments not present." ); - AssemblyItem const& item = *m_expressionClasses.representative(_c).item; - while (SemanticInformation::isCommutativeOperation(item) && + while (SemanticInformation::isCommutativeOperation(*expr.item) && !m_generatedItems.empty() && m_generatedItems.back() == AssemblyItem(Instruction::SWAP1)) // this will not append a swap but remove the one that is already there - appendSwapOrRemove(m_stackHeight - 1); + appendOrRemoveSwap(m_stackHeight - 1); for (auto arg: arguments) if (canBeRemoved(arg, _c)) m_classPositions[arg] = c_invalidPosition; for (size_t i = 0; i < arguments.size(); ++i) m_stack.erase(m_stackHeight - i); - appendItem(*m_expressionClasses.representative(_c).item); - m_stack[m_stackHeight] = _c; - return m_classPositions[_c] = m_stackHeight; + appendItem(*expr.item); + if (expr.item->type() != Operation || instructionInfo(expr.item->instruction()).ret == 1) + { + m_stack[m_stackHeight] = _c; + return m_classPositions[_c] = m_stackHeight; + } + else + { + assertThrow( + instructionInfo(expr.item->instruction()).ret == 0, + OptimizerException, + "Invalid number of return values." + ); + return m_classPositions[_c] = c_invalidPosition; + } +} + +int CSECodeGenerator::classElementPosition(ExpressionClasses::Id _id) const +{ + assertThrow( + m_classPositions.count(_id) && m_classPositions.at(_id) != c_invalidPosition, + OptimizerException, + "Element requested but is not present." + ); + return m_classPositions.at(_id); } bool CSECodeGenerator::canBeRemoved(ExpressionClasses::Id _element, ExpressionClasses::Id _result) @@ -401,22 +507,23 @@ bool CSECodeGenerator::removeStackTopIfPossible() void CSECodeGenerator::appendDup(int _fromPosition) { + assertThrow(_fromPosition != c_invalidPosition, OptimizerException, ""); int nr = 1 + m_stackHeight - _fromPosition; assertThrow(nr <= 16, StackTooDeepException, "Stack too deep."); assertThrow(1 <= nr, OptimizerException, "Invalid stack access."); - m_generatedItems.push_back(AssemblyItem(dupInstruction(nr))); - m_stackHeight++; + appendItem(AssemblyItem(dupInstruction(nr))); m_stack[m_stackHeight] = m_stack[_fromPosition]; } -void CSECodeGenerator::appendSwapOrRemove(int _fromPosition) +void CSECodeGenerator::appendOrRemoveSwap(int _fromPosition) { + assertThrow(_fromPosition != c_invalidPosition, OptimizerException, ""); if (_fromPosition == m_stackHeight) return; int nr = m_stackHeight - _fromPosition; assertThrow(nr <= 16, StackTooDeepException, "Stack too deep."); assertThrow(1 <= nr, OptimizerException, "Invalid stack access."); - m_generatedItems.push_back(AssemblyItem(swapInstruction(nr))); + appendItem(AssemblyItem(swapInstruction(nr))); // The value of a class can be present in multiple locations on the stack. We only update the // "canonical" one that is tracked by m_classPositions if (m_classPositions[m_stack[m_stackHeight]] == m_stackHeight) diff --git a/libevmcore/CommonSubexpressionEliminator.h b/libevmcore/CommonSubexpressionEliminator.h index 331a7642d..c3e291afb 100644 --- a/libevmcore/CommonSubexpressionEliminator.h +++ b/libevmcore/CommonSubexpressionEliminator.h @@ -25,6 +25,8 @@ #include #include +#include +#include #include #include #include @@ -44,9 +46,9 @@ using AssemblyItems = std::vector; * known to be equal only once. * * The general workings are that for each assembly item that is fed into the eliminator, an - * equivalence class is derived from the operation and the equivalence class of its arguments and - * it is assigned to the next sequence number of a stack item. DUPi, SWAPi and some arithmetic - * instructions are used to infer equivalences while these classes are determined. + * equivalence class is derived from the operation and the equivalence class of its arguments. + * DUPi, SWAPi and some arithmetic instructions are used to infer equivalences while these + * classes are determined. * * When the list of optimized items is requested, they are generated in a bottom-up fashion, * adding code for equivalence classes that were not yet computed. @@ -54,6 +56,23 @@ using AssemblyItems = std::vector; class CommonSubexpressionEliminator { public: + struct StorageWriteOperation + { + StorageWriteOperation( + ExpressionClasses::Id _slot, + unsigned _sequenceNumber, + ExpressionClasses::Id _expression + ): slot(_slot), sequenceNumber(_sequenceNumber), expression(_expression) {} + bool operator<(StorageWriteOperation const& _other) const + { + return std::tie(slot, sequenceNumber, expression) < + std::tie(_other.slot, _other.sequenceNumber, _other.expression); + } + ExpressionClasses::Id slot; + unsigned sequenceNumber; + ExpressionClasses::Id expression; + }; + /// Feeds AssemblyItems into the eliminator and @returns the iterator pointing at the first /// item that must be fed into a new instance of the eliminator. template @@ -65,7 +84,7 @@ public: /// Streams debugging information to @a _out. std::ostream& stream( std::ostream& _out, - std::map _currentStack = std::map(), + std::map _initialStack = std::map(), std::map _targetStack = std::map() ) const; @@ -85,10 +104,23 @@ private: /// (must not be positive). ExpressionClasses::Id initialStackElement(int _stackHeight); + /// Increments the sequence number, deletes all storage information that might be overwritten + /// and stores the new value at the given slot. + void storeInStorage(ExpressionClasses::Id _slot, ExpressionClasses::Id _value); + /// Retrieves the current value at the given slot in storage or creates a new special sload class. + ExpressionClasses::Id loadFromStorage(ExpressionClasses::Id _slot); + /// Current stack height, can be negative. int m_stackHeight = 0; /// Current stack layout, mapping stack height -> equivalence class std::map m_stackElements; + /// Current sequence number, this is incremented with each modification to storage. + unsigned m_sequenceNumber = 1; + /// Knowledge about storage content. + std::map m_storageContent; + /// Keeps information about which storage slots were written to at which sequence number with + /// what SSTORE instruction. + std::set m_storageWrites; /// Structure containing the classes of equivalent expressions. ExpressionClasses m_expressionClasses; }; @@ -114,14 +146,19 @@ struct SemanticInformation class CSECodeGenerator { public: - CSECodeGenerator(ExpressionClasses const& _expressionClasses): - m_expressionClasses(_expressionClasses) + using StorageWriteOperation = CommonSubexpressionEliminator::StorageWriteOperation; + + CSECodeGenerator( + ExpressionClasses& _expressionClasses, + std::set const& _storageWrites + ): + m_expressionClasses(_expressionClasses), + m_storageWrites(_storageWrites) {} /// @returns the assembly items generated from the given requirements /// @param _initialStack current contents of the stack (up to stack height of zero) /// @param _targetStackContents final contents of the stack, by stack height relative to initial - /// @param _equivalenceClasses equivalence classes as expressions of how to compute them /// @note should only be called once on each object. AssemblyItems generateCode( std::map const& _initialStack, @@ -133,8 +170,13 @@ private: void addDependencies(ExpressionClasses::Id _c); /// Produce code that generates the given element if it is not yet present. - /// @returns the stack position of the element. - int generateClassElement(ExpressionClasses::Id _c); + /// @returns the stack position of the element or c_invalidPosition if it does not actually + /// generate a value on the stack. + /// @param _allowSequenced indicates that sequence-constrained operations are allowed + int generateClassElement(ExpressionClasses::Id _c, bool _allowSequenced = false); + /// @returns the position of the representative of the given id on the stack. + /// @note throws an exception if it is not on the stack. + int classElementPosition(ExpressionClasses::Id _id) const; /// @returns true if @a _element can be removed - in general or, if given, while computing @a _result. bool canBeRemoved(ExpressionClasses::Id _element, ExpressionClasses::Id _result = ExpressionClasses::Id(-1)); @@ -146,7 +188,7 @@ private: void appendDup(int _fromPosition); /// Appends a swap instruction to m_generatedItems to retrieve the element at the given stack position. /// @note this might also remove the last item if it exactly the same swap instruction. - void appendSwapOrRemove(int _fromPosition); + void appendOrRemoveSwap(int _fromPosition); /// Appends the given assembly item. void appendItem(AssemblyItem const& _item); @@ -163,7 +205,10 @@ private: std::map m_classPositions; /// The actual eqivalence class items and how to compute them. - ExpressionClasses const& m_expressionClasses; + ExpressionClasses& m_expressionClasses; + /// Keeps information about which storage slots were written to at which sequence number with + /// what SSTORE instruction. + std::set const& m_storageWrites; /// The set of equivalence classes that should be present on the stack at the end. std::set m_finalClasses; }; diff --git a/libevmcore/ExpressionClasses.cpp b/libevmcore/ExpressionClasses.cpp index b43b54113..298d11dbd 100644 --- a/libevmcore/ExpressionClasses.cpp +++ b/libevmcore/ExpressionClasses.cpp @@ -39,16 +39,22 @@ bool ExpressionClasses::Expression::operator<(ExpressionClasses::Expression cons { auto type = item->type(); auto otherType = _other.item->type(); - return std::tie(type, item->data(), arguments) < - std::tie(otherType, _other.item->data(), _other.arguments); + return std::tie(type, item->data(), arguments, sequenceNumber) < + std::tie(otherType, _other.item->data(), _other.arguments, _other.sequenceNumber); } -ExpressionClasses::Id ExpressionClasses::find(AssemblyItem const& _item, Ids const& _arguments) +ExpressionClasses::Id ExpressionClasses::find( + AssemblyItem const& _item, + Ids const& _arguments, + bool _copyItem, + unsigned _sequenceNumber +) { Expression exp; exp.id = Id(-1); exp.item = &_item; exp.arguments = _arguments; + exp.sequenceNumber = _sequenceNumber; if (SemanticInformation::isCommutativeOperation(_item)) sort(exp.arguments.begin(), exp.arguments.end()); @@ -58,9 +64,8 @@ ExpressionClasses::Id ExpressionClasses::find(AssemblyItem const& _item, Ids con if (!(e < exp || exp < e)) return e.id; - if (SemanticInformation::isDupInstruction(_item)) + if (_copyItem) { - // Special item that refers to values pre-existing on the stack m_spareAssemblyItem.push_back(make_shared(_item)); exp.item = m_spareAssemblyItem.back().get(); } @@ -74,6 +79,17 @@ ExpressionClasses::Id ExpressionClasses::find(AssemblyItem const& _item, Ids con return exp.id; } +bool ExpressionClasses::knownToBeDifferent(ExpressionClasses::Id _a, ExpressionClasses::Id _b) +{ + // Try to simplify "_a - _b" and return true iff the value is a non-zero constant. + //@todo we could try to cache this information + map matchGroups; + Pattern constant(Push); + constant.setMatchGroup(1, matchGroups); + Id difference = find(Instruction::SUB, {_a, _b}); + return constant.matches(representative(difference), *this) && constant.d() != u256(0); +} + string ExpressionClasses::fullDAGToString(ExpressionClasses::Id _id) const { Expression const& expr = representative(_id); @@ -189,27 +205,46 @@ Rules::Rules() // Moving constants to the outside, order matters here! // we need actions that return expressions (or patterns?) here, and we need also reversed rules // (X+A)+B -> X+(A+B) - m_rules.push_back({ + m_rules += vector>>{{ {op, {{op, {X, A}}, B}}, [=]() -> Pattern { return {op, {X, fun(A.d(), B.d())}}; } - }); + }, { // X+(Y+A) -> (X+Y)+A - m_rules.push_back({ {op, {{op, {X, A}}, Y}}, [=]() -> Pattern { return {op, {{op, {X, Y}}, A}}; } - }); + }, { // For now, we still need explicit commutativity for the inner pattern - m_rules.push_back({ {op, {{op, {A, X}}, B}}, [=]() -> Pattern { return {op, {X, fun(A.d(), B.d())}}; } - }); - m_rules.push_back({ + }, { {op, {{op, {A, X}}, Y}}, [=]() -> Pattern { return {op, {{op, {X, Y}}, A}}; } - }); + }}; + } + // move constants across subtractions + m_rules += vector>>{ + { + // X - A -> X + (-A) + {Instruction::SUB, {X, A}}, + [=]() -> Pattern { return {Instruction::ADD, {X, 0 - A.d()}}; } + }, { + // (X + A) - Y -> (X - Y) + A + {Instruction::SUB, {{Instruction::ADD, {X, A}}, Y}}, + [=]() -> Pattern { return {Instruction::ADD, {{Instruction::SUB, {X, Y}}, A}}; } + }, { + // (A + X) - Y -> (X - Y) + A + {Instruction::SUB, {{Instruction::ADD, {A, X}}, Y}}, + [=]() -> Pattern { return {Instruction::ADD, {{Instruction::SUB, {X, Y}}, A}}; } + }, { + // X - (Y + A) -> (X - Y) + (-A) + {Instruction::SUB, {X, {Instruction::ADD, {Y, A}}}}, + [=]() -> Pattern { return {Instruction::ADD, {{Instruction::SUB, {X, Y}}, 0 - A.d()}}; } + }, { + // X - (A + Y) -> (X - Y) + (-A) + {Instruction::SUB, {X, {Instruction::ADD, {A, Y}}}}, + [=]() -> Pattern { return {Instruction::ADD, {{Instruction::SUB, {X, Y}}, 0 - A.d()}}; } + } }; - - //@todo: (x+8)-3 and other things } ExpressionClasses::Id ExpressionClasses::tryToSimplify(Expression const& _expr, bool _secondRun) @@ -231,7 +266,7 @@ ExpressionClasses::Id ExpressionClasses::tryToSimplify(Expression const& _expr, //cout << ")" << endl; //cout << "with rule " << rule.first.toString() << endl; //ExpressionTemplate t(rule.second()); - //cout << "to" << rule.second().toString() << endl; + //cout << "to " << rule.second().toString() << endl; return rebuildExpression(ExpressionTemplate(rule.second())); } } @@ -254,8 +289,7 @@ ExpressionClasses::Id ExpressionClasses::rebuildExpression(ExpressionTemplate co Ids arguments; for (ExpressionTemplate const& t: _template.arguments) arguments.push_back(rebuildExpression(t)); - m_spareAssemblyItem.push_back(make_shared(_template.item)); - return find(*m_spareAssemblyItem.back(), arguments); + return find(_template.item, arguments); } diff --git a/libevmcore/ExpressionClasses.h b/libevmcore/ExpressionClasses.h index eda568e23..b7868ebb9 100644 --- a/libevmcore/ExpressionClasses.h +++ b/libevmcore/ExpressionClasses.h @@ -52,17 +52,25 @@ public: Id id; AssemblyItem const* item; Ids arguments; + unsigned sequenceNumber; ///< Storage modification sequence, only used for SLOAD/SSTORE instructions. bool operator<(Expression const& _other) const; }; /// Retrieves the id of the expression equivalence class resulting from the given item applied to the /// given classes, might also create a new one. - Id find(AssemblyItem const& _item, Ids const& _arguments = {}); + /// @param _copyItem if true, copies the assembly item to an internal storage instead of just + /// keeping a pointer. + /// The @a _sequenceNumber indicates the current storage access sequence. + Id find(AssemblyItem const& _item, Ids const& _arguments = {}, bool _copyItem = true, unsigned _sequenceNumber = 0); /// @returns the canonical representative of an expression class. Expression const& representative(Id _id) const { return m_representatives.at(_id); } /// @returns the number of classes. Id size() const { return m_representatives.size(); } + /// @returns true if the values of the given classes are known to be different (on every input). + /// @note that this function might still return false for some different inputs. + bool knownToBeDifferent(Id _a, Id _b); + std::string fullDAGToString(Id _id) const; private: diff --git a/test/SolidityOptimizer.cpp b/test/SolidityOptimizer.cpp index 2d5cff7ac..de4cac8fd 100644 --- a/test/SolidityOptimizer.cpp +++ b/test/SolidityOptimizer.cpp @@ -303,6 +303,186 @@ BOOST_AUTO_TEST_CASE(cse_associativity2) 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_SUITE_END() }