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Optimize RETURN x 0 to STOP.

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This commit is contained in:
chriseth 2015-06-12 11:06:05 +02:00
parent a72e357c4e
commit 64a1e82b6c
1 changed files with 30 additions and 18 deletions
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48
CommonSubexpressionEliminator.cpp
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@ -79,31 +79,43 @@ void CommonSubexpressionEliminator::feedItem(AssemblyItem const& _item, bool _co
void CommonSubexpressionEliminator::optimizeBreakingItem()
{
if (!m_breakingItem || *m_breakingItem != AssemblyItem(Instruction::JUMPI))
if (!m_breakingItem)
return;
ExpressionClasses& classes = m_state.expressionClasses();
SourceLocation const& location = m_breakingItem->getLocation();
AssemblyItem::JumpType jumpType = m_breakingItem->getJumpType();
Id condition = m_state.stackElement(m_state.stackHeight() - 1, location);
Id zero = m_state.expressionClasses().find(u256(0));
if (m_state.expressionClasses().knownToBeDifferent(condition, zero))
if (*m_breakingItem == AssemblyItem(Instruction::JUMPI))
{
feedItem(AssemblyItem(Instruction::SWAP1, location), true);
feedItem(AssemblyItem(Instruction::POP, location), true);
AssemblyItem::JumpType jumpType = m_breakingItem->getJumpType();
AssemblyItem item(Instruction::JUMP, location);
item.setJumpType(jumpType);
m_breakingItem = m_state.expressionClasses().storeItem(item);
return;
Id condition = m_state.stackElement(m_state.stackHeight() - 1, location);
if (classes.knownNonZero(condition))
{
feedItem(AssemblyItem(Instruction::SWAP1, location), true);
feedItem(AssemblyItem(Instruction::POP, location), true);
AssemblyItem item(Instruction::JUMP, location);
item.setJumpType(jumpType);
m_breakingItem = classes.storeItem(item);
}
else if (classes.knownZero(condition))
{
AssemblyItem it(Instruction::POP, location);
feedItem(it, true);
feedItem(it, true);
m_breakingItem = nullptr;
}
}
Id negatedCondition = m_state.expressionClasses().find(Instruction::ISZERO, {condition});
if (m_state.expressionClasses().knownToBeDifferent(negatedCondition, zero))
else if (*m_breakingItem == AssemblyItem(Instruction::RETURN))
{
AssemblyItem it(Instruction::POP, location);
feedItem(it, true);
feedItem(it, true);
m_breakingItem = nullptr;
Id size = m_state.stackElement(m_state.stackHeight() - 1, location);
if (classes.knownZero(size))
{
feedItem(AssemblyItem(Instruction::POP, location), true);
feedItem(AssemblyItem(Instruction::POP, location), true);
AssemblyItem item(Instruction::STOP, location);
m_breakingItem = classes.storeItem(item);
}
}
}