AliasClass AliasClass::unionData(rep newBits, AliasClass a, AliasClass b) {
assertx(a.m_stag == b.m_stag);
switch (a.m_stag) {
case STag::None:
break;
case STag::Frame:
case STag::Prop:
case STag::ElemI:
case STag::ElemS:
case STag::MIState:
case STag::Ref:
assertx(!a.equivData(b));
break;
case STag::Stack:
{
auto const stkA = a.m_stack;
auto const stkB = b.m_stack;
// Make a stack range big enough to contain both of them.
auto const highest = std::max(stkA.offset, stkB.offset);
auto const lowest = std::min(lowest_offset(stkA), lowest_offset(stkB));
auto const newStack = AStack { highest, highest - lowest };
auto ret = AliasClass{newBits};
new (&ret.m_stack) AStack(newStack);
ret.m_stag = STag::Stack;
assertx(ret.checkInvariants());
assertx(a <= ret && b <= ret);
return ret;
}
}
return AliasClass{newBits};
}
bool AliasClass::maybeData(AliasClass o) const {
assertx(m_stag == o.m_stag);
switch (m_stag) {
case STag::None:
not_reached(); // handled above
case STag::Frame:
return m_frame.fp == o.m_frame.fp && m_frame.id == o.m_frame.id;
case STag::Prop:
/*
* We can't tell if two objects could be the same from here in general, but
* we can rule out simple cases based on type. The props can't be the same
* if they are at different offsets, though.
*
* For now we're ignoring the type information, and only using offset.
* TODO(#2939547) TODO(#2884927)
*/
if (m_prop.offset != o.m_prop.offset) return false;
return true;
/*
* Two arrays can generally be the same even if they aren't the same SSATmp,
* because we might have loaded it from more than one place, and we have
* linear chains in array modification instructions.
*/
case STag::ElemI:
if (m_elemI.idx != o.m_elemI.idx) return false;
return true;
case STag::ElemS:
if (m_elemS.key != o.m_elemS.key) return false;
return true;
/*
* Stack offsets that have different StkPtr bases are always presumed to
* possibly alias. If both are FramePtrs but different, they can't alias.
* Stack offsets on the same base pointer may only alias if they have
* overlapping ranges.
*/
case STag::Stack:
if (m_stack.base != o.m_stack.base) {
return !(m_stack.base->type() <= Type::FramePtr &&
o.m_stack.base->type() <= Type::FramePtr);
}
{
// True if there's a non-empty intersection of the two stack slot
// intervals.
auto const lowest_upper = std::min(m_stack.offset, o.m_stack.offset);
auto const highest_lower = std::max(
lowest_offset(m_stack),
lowest_offset(o.m_stack)
);
return lowest_upper > highest_lower;
}
case STag::MIState:
return m_mis.offset == o.m_mis.offset;
}
not_reached();
}
bool AliasClass::maybeData(AliasClass o) const {
assertx(m_stag == o.m_stag);
switch (m_stag) {
case STag::None:
not_reached(); // handled outside
case STag::Frame:
return m_frame.fp == o.m_frame.fp && m_frame.id == o.m_frame.id;
case STag::Prop:
/*
* We can't tell if two objects could be the same from here in general, but
* we can rule out simple cases based on type. The props can't be the same
* if they are at different offsets, though.
*
* For now we're ignoring the type information, and only using offset.
* TODO(#2939547) TODO(#2884927)
*/
if (m_prop.offset != o.m_prop.offset) return false;
return true;
/*
* Two arrays can generally be the same even if they aren't the same SSATmp,
* because we might have loaded it from more than one place, and we have
* linear chains in array modification instructions.
*/
case STag::ElemI:
if (m_elemI.idx != o.m_elemI.idx) return false;
return true;
case STag::ElemS:
if (m_elemS.key != o.m_elemS.key) return false;
return true;
case STag::Stack:
{
// True if there's a non-empty intersection of the two stack slot
// intervals.
auto const lowest_upper = std::min(m_stack.offset, o.m_stack.offset);
auto const highest_lower = std::max(
lowest_offset(m_stack),
lowest_offset(o.m_stack)
);
return lowest_upper > highest_lower;
}
case STag::MIState:
return m_mis.offset == o.m_mis.offset;
/*
* Two boxed cells can generally refer to the same RefData.
*/
case STag::Ref:
return true;
}
not_reached();
}
bool AliasClass::subclassData(AliasClass o) const {
switch (m_stag) {
case STag::None:
case STag::Frame:
case STag::Prop:
case STag::ElemI:
case STag::ElemS:
case STag::MIState:
return equivData(o);
case STag::Stack:
if (m_stack.base != o.m_stack.base) return false;
return m_stack.offset <= o.m_stack.offset &&
lowest_offset(m_stack) >= lowest_offset(o.m_stack);
}
not_reached();
}
bool AliasClass::subclassData(AliasClass o) const {
assertx(m_stag == o.m_stag);
switch (m_stag) {
case STag::None:
case STag::Frame:
case STag::Prop:
case STag::ElemI:
case STag::ElemS:
case STag::MIState:
case STag::Ref:
return equivData(o);
case STag::Stack:
return m_stack.offset <= o.m_stack.offset &&
lowest_offset(m_stack) >= lowest_offset(o.m_stack);
}
not_reached();
}
AliasClass AliasClass::unionData(rep newBits, AliasClass a, AliasClass b) {
assertx(a.m_stag == b.m_stag);
switch (a.m_stag) {
case STag::None:
break;
case STag::Frame:
case STag::Prop:
case STag::ElemI:
case STag::ElemS:
case STag::MIState:
case STag::Ref:
assertx(!a.equivData(b));
break;
case STag::Stack:
{
auto const stkA = a.m_stack;
auto const stkB = b.m_stack;
// If two AStack have different bases, we can't union them any better
// than AStackAny, since we don't know where they are relative to each
// other. We know two AStacks with different FramePtr bases can't alias,
// but that doesn't help us represent a union of them.
if (stkA.base != stkB.base) return AliasClass{newBits};
// Make a stack range big enough to contain both of them.
auto const highest = std::max(stkA.offset, stkB.offset);
auto const lowest = std::min(lowest_offset(stkA), lowest_offset(stkB));
auto const newStack = AStack {
stkA.base,
highest,
highest - lowest
};
auto ret = AliasClass{newBits};
new (&ret.m_stack) AStack(newStack);
ret.m_stag = STag::Stack;
assertx(ret.checkInvariants());
assertx(a <= ret && b <= ret);
return ret;
}
}
return AliasClass{newBits};
}