AliasClass AliasClass::operator|(AliasClass o) const {
if (auto const c = precise_union(o)) return *c;
auto const unioned = static_cast<rep>(m_bits | o.m_bits);
// If they have the same stag, try to merge them with unionData.
auto stag1 = m_stag;
auto stag2 = o.m_stag;
if (stag1 == stag2) return unionData(unioned, *this, o);
// If one of the alias classes have a non-None stag, we can only keep it if
// the other doesn't have the corresponding bit set.
if (stag1 != STag::None && (o.m_bits & stagBit(stag1))) stag1 = STag::None;
if (stag2 != STag::None && (m_bits & stagBit(stag2))) stag2 = STag::None;
auto ret = AliasClass{unioned};
if (stag1 == stag2) return ret; // both None.
// Note: union operations are guaranteed to be commutative, so if there are
// two non-None stags, we have to consistently choose between them. For now
// we keep the one with a smaller `rep' value, instead of discarding both.
const AliasClass* chosen = &o;
auto stag = stag2;
if (stag1 != STag::None) {
if (stag2 == STag::None || stagBit(stag1) < stagBit(stag2)) {
chosen = this;
stag = stag1;
}
}
switch (stag) {
case STag::None:
break;
case STag::Frame: new (&ret.m_frame) AFrame(chosen->m_frame); break;
case STag::Prop: new (&ret.m_prop) AProp(chosen->m_prop); break;
case STag::ElemI: new (&ret.m_elemI) AElemI(chosen->m_elemI); break;
case STag::ElemS: new (&ret.m_elemS) AElemS(chosen->m_elemS); break;
case STag::Stack: new (&ret.m_stack) AStack(chosen->m_stack); break;
case STag::MIState: new (&ret.m_mis) AMIState(chosen->m_mis); break;
case STag::Ref: new (&ret.m_ref) ARef(chosen->m_ref); break;
}
ret.m_stag = stag;
return ret;
}
AliasClass AliasClass::operator|(AliasClass o) const {
if (o <= *this) return *this;
if (*this <= o) return o;
auto const unioned = static_cast<rep>(m_bits | o.m_bits);
// Note: union operations are guaranteed to be commutative, so if there are
// two non-None stags, we have to consistently choose between them. For now
// we throw both away in any case where they differ, and try to merge them
// with unionData if they are the same. If only one had an stag, we can keep
// it only if the other didn't have that bit set.
auto const stag1 = m_stag;
auto const stag2 = o.m_stag;
if (stag1 == stag2) return unionData(unioned, *this, o);
if (stag1 != STag::None && stag2 != STag::None) {
return AliasClass{unioned};
}
if (stag2 != STag::None) return o | *this;
if (o.m_bits & stagBit(stag1)) {
return AliasClass{unioned};
}
auto ret = AliasClass{unioned};
switch (stag1) {
case STag::None:
break;
case STag::Frame: new (&ret.m_frame) AFrame(m_frame); break;
case STag::Prop: new (&ret.m_prop) AProp(m_prop); break;
case STag::ElemI: new (&ret.m_elemI) AElemI(m_elemI); break;
case STag::ElemS: new (&ret.m_elemS) AElemS(m_elemS); break;
case STag::Stack: new (&ret.m_stack) AStack(m_stack); break;
case STag::MIState: new (&ret.m_mis) AMIState(m_mis); break;
}
ret.m_stag = stag1;
return ret;
}
