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Use rematerializer if variable is unreferenced or value is "cheap".

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This commit is contained in:
chriseth
2019-01-07 14:03:32 +01:00
parent aca9e58145
commit 2e9c70add0
23 changed files with 261 additions and 127 deletions
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libyul/optimiser/Rematerialiser.cpp
+23 -3
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@@ -22,6 +22,7 @@
#include <libyul/optimiser/Metrics.h>
#include <libyul/optimiser/ASTCopier.h>
#include <libyul/optimiser/NameCollector.h>
#include <libyul/Exceptions.h>
#include <libyul/AsmData.h>
@@ -29,6 +30,16 @@ using namespace std;
using namespace dev;
using namespace yul;
void Rematerialiser::run(Block& _ast)
{
Rematerialiser{_ast}(_ast);
}
Rematerialiser::Rematerialiser(Block& _ast):
m_referenceCounts(ReferencesCounter::countReferences(_ast))
{
}
void Rematerialiser::visit(Expression& _e)
{
if (_e.type() == typeid(Identifier))
@@ -37,12 +48,21 @@ void Rematerialiser::visit(Expression& _e)
if (m_value.count(identifier.name))
{
YulString name = identifier.name;
for (auto const& ref: m_references[name])
assertThrow(inScope(ref), OptimizerException, "");
assertThrow(m_value.at(name), OptimizerException, "");
auto const& value = *m_value.at(name);
if (CodeSize::codeSize(value) <= 7)
size_t refs = m_referenceCounts[name];
size_t cost = CodeCost::codeCost(value);
if (refs <= 1 || cost == 0 || (refs <= 5 && cost <= 1))
{
assertThrow(m_referenceCounts[name] > 0, OptimizerException, "");
for (auto const& ref: m_references[name])
assertThrow(inScope(ref), OptimizerException, "");
// update reference counts
m_referenceCounts[name]--;
for (auto const& ref: ReferencesCounter::countReferences(value))
m_referenceCounts[ref.first] += ref.second;
_e = (ASTCopier{}).translate(value);
}
}
}
DataFlowAnalyzer::visit(_e);