bool hasObviousStackOutput()

in hphp/hhbbc/optimize.cpp [216:311]

• 87 lines of code
• 73 McCabe index (conditional complexity)

bool hasObviousStackOutput(const Bytecode& op, const Interp& interp) {
  switch (op.op) {
  case Op::Null:
  case Op::NullUninit:
  case Op::True:
  case Op::False:
  case Op::Int:
  case Op::Double:
  case Op::String:
  case Op::LazyClass:
  case Op::Dict:
  case Op::Vec:
  case Op::Keyset:
  case Op::NewDictArray:
  case Op::NewStructDict:
  case Op::NewVec:
  case Op::NewKeysetArray:
  case Op::AddNewElemC:
  case Op::NewCol:
  case Op::NewPair:
  case Op::ClassName:
  case Op::LazyClassFromClass:
  case Op::File:
  case Op::Dir:
  case Op::Concat:
  case Op::ConcatN:
  case Op::Not:
  case Op::Same:
  case Op::NSame:
  case Op::Eq:
  case Op::Neq:
  case Op::Lt:
  case Op::Gt:
  case Op::Lte:
  case Op::Gte:
  case Op::Cmp:
  case Op::Shl:
  case Op::Shr:
  case Op::CastBool:
  case Op::CastInt:
  case Op::CastDouble:
  case Op::CastString:
  case Op::CastDict:
  case Op::CastVec:
  case Op::CastKeyset:
  case Op::DblAsBits:
  case Op::InstanceOfD:
  case Op::IsLateBoundCls:
  case Op::IsTypeStructC:
  case Op::CombineAndResolveTypeStruct:
  case Op::RecordReifiedGeneric:
  case Op::InstanceOf:
  case Op::Print:
  case Op::Exit:
  case Op::AKExists:
  case Op::IssetL:
  case Op::IsUnsetL:
  case Op::IssetG:
  case Op::IssetS:
  case Op::IsTypeC:
  case Op::IsTypeL:
  case Op::OODeclExists:
    return true;

  case Op::This:
  case Op::BareThis:
    if (auto tt = thisType(interp.index, interp.ctx)) {
      auto t = interp.state.stack.back().type;
      if (t.couldBe(BInitNull) && !t.subtypeOf(BInitNull)) {
        t = unopt(std::move(t));
      }
      return !t.strictSubtypeOf(*tt);
    }
    return true;

  case Op::CGetL:
  case Op::CGetQuietL:
  case Op::CUGetL:
  case Op::CGetL2:
  case Op::PushL:
    return true;

  // The output of SetL is obvious if you know what its input is
  // (which we'll assert if we know).
  case Op::SetL:
    return true;

  // The output of SetM isn't quite as obvious as SetL, but the jit
  // can work it out from the input just as well as hhbbc (if not better).
  case Op::SetM:
    return true;

  default:
    return false;
  }
}