Type typeIncDec(IncDecOp op, Type t) {
auto const overflowToDbl = isIncDecO(op);
auto const val = tv(t);
if (!val) {
// Doubles always stay doubles
if (t.subtypeOf(TDbl)) return TDbl;
// Ints stay ints unless they can overflow to doubles
if (t.subtypeOf(TInt)) {
return overflowToDbl ? TNum : TInt;
}
// Null goes to 1 on ++, stays null on --. Uninit is folded to init.
if (t.subtypeOf(TNull)) {
return isInc(op) ? ival(1) : TInitNull;
}
// No-op on bool, array, resource, object.
if (t.subtypeOfAny(TBool, TArr, TRes, TObj, TVec, TDict, TKeyset)) return t;
// Last unhandled case: strings. These result in Int|Str because of the
// behavior on strictly-numeric strings, and we can't express that yet.
return TInitCell;
}
auto const inc = isInc(op);
// We can't constprop with this eval_cell, because of the effects
// on locals.
auto resultTy = eval_cell([inc,overflowToDbl,val] {
auto c = *val;
if (inc) {
(overflowToDbl ? cellIncO : cellInc)(c);
} else {
(overflowToDbl ? cellDecO : cellDec)(c);
}
return c;
});
if (!resultTy) resultTy = TInitCell;
// We may have inferred a TSStr or TSArr with a value here, but at
// runtime it will not be static.
resultTy = loosen_staticness(*resultTy);
return *resultTy;
}
void
IRTranslator::translateIncDecL(const NormalizedInstruction& i) {
auto const op = static_cast<IncDecOp>(i.imm[1].u_OA);
HHIR_EMIT(IncDecL, isPre(op), isInc(op), isIncDecO(op), i.imm[0].u_LA);
}