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https://github.com/ethereum/solidity
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Merge pull request #1429 from ethereum/unreachablepeephole
Some dead code elimination
This commit is contained in:
chriseth
GitHub
commit
0933a4ff1a
@ -1,5 +1,8 @@
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### 0.4.7 (unreleased)
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Features:
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* Optimizer: Some dead code elimination.
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Bugfixes:
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* Type checker: string literals that are not valid UTF-8 cannot be converted to string type
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@ -337,7 +337,7 @@ map<u256, u256> Assembly::optimiseInternal(bool _enable, bool _isCreation, size_
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count = 0;
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PeepholeOptimiser peepOpt(m_items);
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if (peepOpt.optimise())
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while (peepOpt.optimise())
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count++;
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if (!_enable)
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@ -30,51 +30,96 @@ using namespace dev;
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// TODO: Extend this to use the tools from ExpressionClasses.cpp
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struct Identity
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struct OptimiserState
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{
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static size_t windowSize() { return 1; }
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static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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AssemblyItems const& items;
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size_t i;
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std::back_insert_iterator<AssemblyItems> out;
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};
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template <class Method, size_t Arguments>
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struct ApplyRule
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{
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};
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template <class Method>
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struct ApplyRule<Method, 3>
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{
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static bool applyRule(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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{
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*_out = *_in;
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return true;
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return Method::applySimple(_in[0], _in[1], _in[2], _out);
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}
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};
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template <class Method>
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struct ApplyRule<Method, 2>
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{
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static bool applyRule(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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{
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return Method::applySimple(_in[0], _in[1], _out);
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}
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};
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template <class Method>
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struct ApplyRule<Method, 1>
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{
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static bool applyRule(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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{
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return Method::applySimple(_in[0], _out);
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}
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};
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struct PushPop
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template <class Method, size_t WindowSize>
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struct SimplePeepholeOptimizerMethod
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{
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static size_t windowSize() { return 2; }
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static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems>)
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static bool apply(OptimiserState& _state)
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{
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auto t = _in[0].type();
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if (_in[1] == Instruction::POP && (
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SemanticInformation::isDupInstruction(_in[0]) ||
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t == Push || t == PushString || t == PushTag || t == PushSub ||
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t == PushSubSize || t == PushProgramSize || t == PushData || t == PushLibraryAddress
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))
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if (
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_state.i + WindowSize <= _state.items.size() &&
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ApplyRule<Method, WindowSize>::applyRule(_state.items.begin() + _state.i, _state.out)
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)
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{
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_state.i += WindowSize;
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return true;
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}
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else
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return false;
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}
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};
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struct AddPop
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struct Identity: SimplePeepholeOptimizerMethod<Identity, 1>
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{
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static size_t windowSize() { return 2; }
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static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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static bool applySimple(AssemblyItem const& _item, std::back_insert_iterator<AssemblyItems> _out)
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{
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if (_in[1] == Instruction::POP &&
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_in[0].type() == Operation
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)
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*_out = _item;
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return true;
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}
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};
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struct PushPop: SimplePeepholeOptimizerMethod<PushPop, 2>
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{
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static bool applySimple(AssemblyItem const& _push, AssemblyItem const& _pop, std::back_insert_iterator<AssemblyItems>)
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{
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auto t = _push.type();
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return _pop == Instruction::POP && (
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SemanticInformation::isDupInstruction(_push) ||
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t == Push || t == PushString || t == PushTag || t == PushSub ||
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t == PushSubSize || t == PushProgramSize || t == PushData || t == PushLibraryAddress
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);
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}
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};
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struct OpPop: SimplePeepholeOptimizerMethod<OpPop, 2>
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{
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static bool applySimple(
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AssemblyItem const& _op,
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AssemblyItem const& _pop,
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std::back_insert_iterator<AssemblyItems> _out
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)
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{
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if (_pop == Instruction::POP && _op.type() == Operation)
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{
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Instruction i0 = _in[0].instruction();
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if (instructionInfo(i0).ret == 1 &&
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!SemanticInformation::invalidatesMemory(i0) &&
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!SemanticInformation::invalidatesStorage(i0) &&
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!SemanticInformation::altersControlFlow(i0) &&
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!instructionInfo(i0).sideEffects
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)
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Instruction instr = _op.instruction();
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if (instructionInfo(instr).ret == 1 && !instructionInfo(instr).sideEffects)
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{
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for (int j = 0; j < instructionInfo(i0).args; j++)
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for (int j = 0; j < instructionInfo(instr).args; j++)
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*_out = Instruction::POP;
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return true;
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}
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@ -83,33 +128,33 @@ struct AddPop
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}
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};
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struct DoubleSwap
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struct DoubleSwap: SimplePeepholeOptimizerMethod<DoubleSwap, 2>
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{
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static size_t windowSize() { return 2; }
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static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems>)
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static size_t applySimple(AssemblyItem const& _s1, AssemblyItem const& _s2, std::back_insert_iterator<AssemblyItems>)
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{
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if (_in[0] == _in[1] && SemanticInformation::isSwapInstruction(_in[0]))
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return true;
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else
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return false;
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return _s1 == _s2 && SemanticInformation::isSwapInstruction(_s1);
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}
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};
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struct JumpToNext
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struct JumpToNext: SimplePeepholeOptimizerMethod<JumpToNext, 3>
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{
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static size_t windowSize() { return 3; }
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static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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static size_t applySimple(
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AssemblyItem const& _pushTag,
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AssemblyItem const& _jump,
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AssemblyItem const& _tag,
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std::back_insert_iterator<AssemblyItems> _out
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)
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{
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if (
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_in[0].type() == PushTag &&
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(_in[1] == Instruction::JUMP || _in[1] == Instruction::JUMPI) &&
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_in[2].type() == Tag &&
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_in[0].data() == _in[2].data()
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_pushTag.type() == PushTag &&
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(_jump == Instruction::JUMP || _jump == Instruction::JUMPI) &&
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_tag.type() == Tag &&
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_pushTag.data() == _tag.data()
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)
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{
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if (_in[1] == Instruction::JUMPI)
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*_out = AssemblyItem(Instruction::POP, _in[1].location());
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*_out = _in[2];
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if (_jump == Instruction::JUMPI)
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*_out = AssemblyItem(Instruction::POP, _jump.location());
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*_out = _tag;
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return true;
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}
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else
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@ -117,19 +162,23 @@ struct JumpToNext
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}
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};
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struct TagConjunctions
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struct TagConjunctions: SimplePeepholeOptimizerMethod<TagConjunctions, 3>
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{
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static size_t windowSize() { return 3; }
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static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
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static bool applySimple(
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AssemblyItem const& _pushTag,
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AssemblyItem const& _pushConstant,
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AssemblyItem const& _and,
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std::back_insert_iterator<AssemblyItems> _out
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)
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{
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if (
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_in[0].type() == PushTag &&
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_in[2] == Instruction::AND &&
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_in[1].type() == Push &&
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(_in[1].data() & u256(0xFFFFFFFF)) == u256(0xFFFFFFFF)
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_pushTag.type() == PushTag &&
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_and == Instruction::AND &&
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_pushConstant.type() == Push &&
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(_pushConstant.data() & u256(0xFFFFFFFF)) == u256(0xFFFFFFFF)
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)
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{
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*_out = _in[0];
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*_out = _pushTag;
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return true;
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}
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else
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@ -137,11 +186,35 @@ struct TagConjunctions
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}
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};
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struct OptimiserState
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/// Removes everything after a JUMP (or similar) until the next JUMPDEST.
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struct UnreachableCode
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{
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AssemblyItems const& items;
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size_t i;
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std::back_insert_iterator<AssemblyItems> out;
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static bool apply(OptimiserState& _state)
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{
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auto it = _state.items.begin() + _state.i;
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auto end = _state.items.end();
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if (it == end)
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return false;
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if (
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it[0] != Instruction::JUMP &&
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it[0] != Instruction::RETURN &&
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it[0] != Instruction::STOP &&
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it[0] != Instruction::SUICIDE
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)
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return false;
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size_t i = 1;
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while (it + i != end && it[i].type() != Tag)
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i++;
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if (i > 1)
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{
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*_state.out = it[0];
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_state.i += i;
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return true;
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}
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else
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return false;
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}
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};
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void applyMethods(OptimiserState&)
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@ -152,9 +225,7 @@ void applyMethods(OptimiserState&)
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template <typename Method, typename... OtherMethods>
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void applyMethods(OptimiserState& _state, Method, OtherMethods... _other)
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{
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if (_state.i + Method::windowSize() <= _state.items.size() && Method::apply(_state.items.begin() + _state.i, _state.out))
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_state.i += Method::windowSize();
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else
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if (!Method::apply(_state))
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applyMethods(_state, _other...);
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}
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@ -162,7 +233,7 @@ bool PeepholeOptimiser::optimise()
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{
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OptimiserState state {m_items, 0, std::back_inserter(m_optimisedItems)};
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while (state.i < m_items.size())
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applyMethods(state, PushPop(), AddPop(), DoubleSwap(), JumpToNext(), TagConjunctions(), Identity());
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applyMethods(state, PushPop(), OpPop(), DoubleSwap(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity());
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if (m_optimisedItems.size() < m_items.size())
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{
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m_items = std::move(m_optimisedItems);
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@ -20,17 +20,21 @@
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* Tests for the Solidity optimizer.
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*/
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#include <string>
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#include <tuple>
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#include <memory>
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#include <boost/test/unit_test.hpp>
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#include <boost/lexical_cast.hpp>
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#include <test/libsolidity/SolidityExecutionFramework.h>
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#include <libevmasm/CommonSubexpressionEliminator.h>
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#include <libevmasm/PeepholeOptimiser.h>
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#include <libevmasm/ControlFlowGraph.h>
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#include <libevmasm/Assembly.h>
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#include <libevmasm/BlockDeduplicator.h>
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#include <boost/test/unit_test.hpp>
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#include <boost/lexical_cast.hpp>
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#include <string>
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#include <tuple>
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#include <memory>
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using namespace std;
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using namespace dev::eth;
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@ -1121,6 +1125,40 @@ BOOST_AUTO_TEST_CASE(block_deduplicator_loops)
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BOOST_CHECK_EQUAL(pushTags.size(), 1);
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}
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BOOST_AUTO_TEST_CASE(clear_unreachable_code)
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{
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AssemblyItems items{
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AssemblyItem(PushTag, 1),
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Instruction::JUMP,
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u256(0),
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Instruction::SLOAD,
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AssemblyItem(Tag, 2),
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u256(5),
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u256(6),
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Instruction::SSTORE,
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AssemblyItem(PushTag, 1),
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Instruction::JUMP,
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u256(5),
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u256(6)
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};
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AssemblyItems expectation{
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AssemblyItem(PushTag, 1),
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Instruction::JUMP,
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AssemblyItem(Tag, 2),
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u256(5),
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u256(6),
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Instruction::SSTORE,
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AssemblyItem(PushTag, 1),
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Instruction::JUMP
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};
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PeepholeOptimiser peepOpt(items);
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BOOST_REQUIRE(peepOpt.optimise());
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BOOST_CHECK_EQUAL_COLLECTIONS(
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items.begin(), items.end(),
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expectation.begin(), expectation.end()
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);
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}
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BOOST_AUTO_TEST_CASE(computing_constants)
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{
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char const* sourceCode = R"(
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