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Introduce fine-grained optimiser settings in libevmasm

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This commit is contained in:
Alex Beregszaszi 2017-06-30 22:10:55 +01:00
parent 89fadd6935
commit f9d5f7e497
2 changed files with 62 additions and 19 deletions
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63
libevmasm/Assembly.cpp
View File

@ -350,38 +350,65 @@ void Assembly::injectStart(AssemblyItem const& _i)
Assembly& Assembly::optimise(bool _enable, bool _isCreation, size_t _runs)
{
optimiseInternal(_enable, _isCreation, _runs);
OptimiserSettings settings;
settings.isCreation = _isCreation;
settings.runPeephole = true;
if (_enable)
{
settings.runDeduplicate = true;
settings.runCSE = true;
settings.runConstantOptimiser = true;
}
settings.expectedExecutionsPerDeployment = _runs;
optimiseInternal(settings);
return *this;
}
map<u256, u256> Assembly::optimiseInternal(bool _enable, bool _isCreation, size_t _runs)
Assembly& Assembly::optimise(OptimiserSettings _settings)
{
optimiseInternal(_settings);
return *this;
}
map<u256, u256> Assembly::optimiseInternal(OptimiserSettings _settings)
{
// Run optimisation for sub-assemblies.
for (size_t subId = 0; subId < m_subs.size(); ++subId)
{
map<u256, u256> subTagReplacements = m_subs[subId]->optimiseInternal(_enable, false, _runs);
OptimiserSettings settings = _settings;
// Disable creation mode for sub-assemblies.
settings.isCreation = false;
map<u256, u256> subTagReplacements = m_subs[subId]->optimiseInternal(settings);
// Apply the replacements (can be empty).
BlockDeduplicator::applyTagReplacement(m_items, subTagReplacements, subId);
}
map<u256, u256> tagReplacements;
// Iterate until no new optimisation possibilities are found.
for (unsigned count = 1; count > 0;)
{
count = 0;
PeepholeOptimiser peepOpt(m_items);
while (peepOpt.optimise())
count++;
if (!_enable)
continue;
// This only modifies PushTags, we have to run again to actually remove code.
BlockDeduplicator dedup(m_items);
if (dedup.deduplicate())
if (_settings.runPeephole)
{
tagReplacements.insert(dedup.replacedTags().begin(), dedup.replacedTags().end());
count++;
PeepholeOptimiser peepOpt(m_items);
while (peepOpt.optimise())
count++;
}
// This only modifies PushTags, we have to run again to actually remove code.
if (_settings.runDeduplicate)
{
BlockDeduplicator dedup(m_items);
if (dedup.deduplicate())
{
tagReplacements.insert(dedup.replacedTags().begin(), dedup.replacedTags().end());
count++;
}
}
if (_settings.runCSE)
{
// Control flow graph optimization has been here before but is disabled because it
// assumes we only jump to tags that are pushed. This is not the case anymore with
@ -429,10 +456,10 @@ map<u256, u256> Assembly::optimiseInternal(bool _enable, bool _isCreation, size_
}
}
if (_enable)
if (_settings.runConstantOptimiser)
ConstantOptimisationMethod::optimiseConstants(
_isCreation,
_isCreation ? 1 : _runs,
_settings.isCreation,
_settings.isCreation ? 1 : _settings.expectedExecutionsPerDeployment,
*this,
m_items
);

18
libevmasm/Assembly.h
View File

@ -97,12 +97,28 @@ public:
LinkerObject const& assemble() const;
bytes const& data(h256 const& _i) const { return m_data.at(_i); }
struct OptimiserSettings
{
bool isCreation = false;
bool runPeephole = false;
bool runDeduplicate = false;
bool runCSE = false;
bool runConstantOptimiser = false;
/// This specifies an estimate on how often each opcode in this assembly will be executed,
/// i.e. use a small value to optimise for size and a large value to optimise for runtime gas usage.
size_t expectedExecutionsPerDeployment = 200;
};
/// Execute optimisation passes as defined by @a _settings and return the optimised assembly.
Assembly& optimise(OptimiserSettings _settings);
/// Modify (if @a _enable is set) and return the current assembly such that creation and
/// execution gas usage is optimised. @a _isCreation should be true for the top-level assembly.
/// @a _runs specifes an estimate on how often each opcode in this assembly will be executed,
/// i.e. use a small value to optimise for size and a large value to optimise for runtime.
/// If @a _enable is not set, will perform some simple peephole optimizations.
Assembly& optimise(bool _enable, bool _isCreation = true, size_t _runs = 200);
Json::Value stream(
std::ostream& _out,
std::string const& _prefix = "",
@ -113,7 +129,7 @@ public:
protected:
/// Does the same operations as @a optimise, but should only be applied to a sub and
/// returns the replaced tags.
std::map<u256, u256> optimiseInternal(bool _enable, bool _isCreation, size_t _runs);
std::map<u256, u256> optimiseInternal(OptimiserSettings _settings);
unsigned bytesRequired(unsigned subTagSize) const;