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This commit is contained in:
chriseth 2022-11-10 18:02:56 +01:00
parent 695b250557
commit 3ac6edec5b
1 changed files with 20 additions and 13 deletions
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33
libyul/optimiser/KnowledgeBase.cpp
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@ -52,7 +52,7 @@ optional<u256> KnowledgeBase::differenceIfKnownConstant(YulString _a, YulString
if (offA.reference == offB.reference) if (offA.reference == offB.reference)
return offA.offset - offB.offset; return offA.offset - offB.offset;
else else
return {}; return nullopt;
} }
@ -66,13 +66,13 @@ bool KnowledgeBase::knownToBeDifferentByAtLeast32(YulString _a, YulString _b)
bool KnowledgeBase::knownToBeZero(YulString _a) bool KnowledgeBase::knownToBeZero(YulString _a)
{ {
return valueIfKnownConstant(_a) == u256{}; return valueIfKnownConstant(_a) == 0;
} }
optional<u256> KnowledgeBase::valueIfKnownConstant(YulString _a) optional<u256> KnowledgeBase::valueIfKnownConstant(YulString _a)
{ {
VariableOffset offset = explore(_a); VariableOffset offset = explore(_a);
if (offset.reference == YulString{}) if (offset.reference.empty())
return offset.offset; return offset.offset;
else else
return nullopt; return nullopt;
@ -85,7 +85,7 @@ optional<u256> KnowledgeBase::valueIfKnownConstant(Expression const& _expression
else if (Literal const* lit = get_if<Literal>(&_expression)) else if (Literal const* lit = get_if<Literal>(&_expression))
return valueOfLiteral(*lit); return valueOfLiteral(*lit);
else else
return {}; return nullopt;
} }
KnowledgeBase::VariableOffset KnowledgeBase::explore(YulString _var) KnowledgeBase::VariableOffset KnowledgeBase::explore(YulString _var)
@ -117,9 +117,9 @@ KnowledgeBase::VariableOffset KnowledgeBase::explore(YulString _var)
optional<KnowledgeBase::VariableOffset> KnowledgeBase::explore(Expression const& _value) optional<KnowledgeBase::VariableOffset> KnowledgeBase::explore(Expression const& _value)
{ {
if (Literal const* literal = std::get_if<Literal>(&_value)) if (Literal const* literal = get_if<Literal>(&_value))
return VariableOffset{YulString{}, valueOfLiteral(*literal)}; return VariableOffset{YulString{}, valueOfLiteral(*literal)};
else if (Identifier const* identifier = std::get_if<Identifier>(&_value)) else if (Identifier const* identifier = get_if<Identifier>(&_value))
return explore(identifier->name); return explore(identifier->name);
else if (FunctionCall const* f = get_if<FunctionCall>(&_value)) else if (FunctionCall const* f = get_if<FunctionCall>(&_value))
{ {
@ -150,7 +150,7 @@ optional<KnowledgeBase::VariableOffset> KnowledgeBase::explore(Expression const&
} }
} }
return {}; return nullopt;
} }
Expression const* KnowledgeBase::valueOf(YulString _var) Expression const* KnowledgeBase::valueOf(YulString _var)
@ -175,26 +175,33 @@ void KnowledgeBase::reset(YulString _var)
if (VariableOffset const* offset = util::valueOrNullptr(m_offsets, _var)) if (VariableOffset const* offset = util::valueOrNullptr(m_offsets, _var))
{ {
// Remove var from its group // Remove var from its group
if (offset->reference != YulString{}) if (!offset->reference.empty())
m_groupMembers[offset->reference].erase(_var); m_groupMembers[offset->reference].erase(_var);
m_offsets.erase(_var); m_offsets.erase(_var);
} }
if (set<YulString>* group = util::valueOrNullptr(m_groupMembers, _var)) if (set<YulString>* group = util::valueOrNullptr(m_groupMembers, _var))
{ {
// _var was a representative, we might have to find a new one. // _var was a representative, we might have to find a new one.
if (group->empty()) if (!group->empty())
m_groupMembers.erase(_var);
else
{ {
YulString newRepresentative = *group->begin(); YulString newRepresentative = *group->begin();
yulAssert(newRepresentative != _var);
u256 newOffset = m_offsets[newRepresentative].offset; u256 newOffset = m_offsets[newRepresentative].offset;
// newOffset = newRepresentative - _var
for (YulString groupMember: *group) for (YulString groupMember: *group)
{ {
yulAssert(m_offsets[groupMember].reference == _var); yulAssert(m_offsets[groupMember].reference == _var);
m_offsets[groupMember].reference = newRepresentative; m_offsets[groupMember].reference = newRepresentative;
m_offsets[newRepresentative].offset -= newOffset; // groupMember = _var + m_offsets[groupMember].offset (old)
// = newRepresentative - newOffset + m_offsets[groupMember].offset (old)
// so subtracting newOffset from .offset yields the original relation again,
// just with _var replaced by newRepresentative
m_offsets[groupMember].offset -= newOffset;
} }
m_groupMembers[newRepresentative] = std::move(*group);
} }
m_groupMembers.erase(_var);
} }
} }
@ -203,7 +210,7 @@ KnowledgeBase::VariableOffset KnowledgeBase::setOffset(YulString _variable, Vari
m_offsets[_variable] = _value; m_offsets[_variable] = _value;
// Constants are not tracked in m_groupMembers because // Constants are not tracked in m_groupMembers because
// the "representative" can never be reset. // the "representative" can never be reset.
if (_value.reference != YulString{}) if (!_value.reference.empty())
m_groupMembers[_value.reference].insert(_variable); m_groupMembers[_value.reference].insert(_variable);
return _value; return _value;
} }