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Merge pull request #3077 from ethereum/optimze_pops

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Assume peephole optimizer was successful if number of pops increased.
This commit is contained in:
chriseth 2017-10-16 22:11:45 +02:00 committed by GitHub
commit 7989fc4c35
4 changed files with 27 additions and 2 deletions
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1
Changelog.md
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@ -13,6 +13,7 @@ Features:
* Type Checker: Require ``storage`` or ``memory`` keyword for local variables as experimental 0.5.0 feature.
Bugfixes:
* Optimizer: Remove unused stack computation results.
* Parser: Fix source location of VariableDeclarationStatement.
* Type Checker: Properly check array length and don't rely on an assertion in code generation.
* Type Checker: Properly support overwriting members inherited from ``address`` in a contract

3
libevmasm/Assembly.cpp
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@ -408,7 +408,10 @@ map<u256, u256> Assembly::optimiseInternal(
{
PeepholeOptimiser peepOpt(m_items);
while (peepOpt.optimise())
{
count++;
assertThrow(count < 64000, OptimizerException, "Peephole optimizer seems to be stuck.");
}
}
// This only modifies PushTags, we have to run again to actually remove code.

11
libevmasm/PeepholeOptimiser.cpp
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@ -249,6 +249,11 @@ void applyMethods(OptimiserState& _state, Method, OtherMethods... _other)
applyMethods(_state, _other...);
}
size_t numberOfPops(AssemblyItems const& _items)
{
return std::count(_items.begin(), _items.end(), Instruction::POP);
}
}
bool PeepholeOptimiser::optimise()
@ -257,8 +262,10 @@ bool PeepholeOptimiser::optimise()
while (state.i < m_items.size())
applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), 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)
m_optimisedItems.size() == m_items.size() && (
eth::bytesRequired(m_optimisedItems, 3) < eth::bytesRequired(m_items, 3) ||
numberOfPops(m_optimisedItems) > numberOfPops(m_items)
)
))
{
m_items = std::move(m_optimisedItems);

14
test/libevmasm/Optimiser.cpp
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@ -841,6 +841,20 @@ BOOST_AUTO_TEST_CASE(peephole_double_push)
);
}
BOOST_AUTO_TEST_CASE(peephole_pop_calldatasize)
{
AssemblyItems items{
u256(4),
Instruction::CALLDATASIZE,
Instruction::LT,
Instruction::POP
};
PeepholeOptimiser peepOpt(items);
for (size_t i = 0; i < 3; i++)
BOOST_CHECK(peepOpt.optimise());
BOOST_CHECK(items.empty());
}
BOOST_AUTO_TEST_CASE(jumpdest_removal)
{
AssemblyItems items{