//
// Assumes 'parent' is a PRIM_MOVE or PRIM_ASSIGN
//
// Returns false if the LHS of the move/assign indicates that the rhs cannot
// be a const-ref. For example, if we have a case like this:
//
// (move A, (set-reference B))
//
// where 'A' and 'B' are references, B cannot be a const-ref if A is not a
// const-ref.
//
// In the case of a dereference, (move A, (deref B)), this function will return
// true because we're simply reading B.
//
static bool canRHSBeConstRef(CallExpr* parent, SymExpr* use) {
INT_ASSERT(isMoveOrAssign(parent));
SymExpr* LHS = toSymExpr(parent->get(1));
CallExpr* rhs = toCallExpr(parent->get(2));
INT_ASSERT(rhs);
switch (rhs->primitive->tag) {
case PRIM_GET_MEMBER:
case PRIM_GET_MEMBER_VALUE:
case PRIM_GET_SVEC_MEMBER:
case PRIM_GET_SVEC_MEMBER_VALUE:
case PRIM_GET_REAL:
case PRIM_GET_IMAG:
case PRIM_ADDR_OF:
case PRIM_SET_REFERENCE: {
// If LHS is a reference and is not a const-ref, the reference in 'rhs'
// should not be considered a const-ref either.
//
// For the get-member primitives, I intend this to be a safe approach
// until we know what const-ref means for fields. Basically, if any field
// might be modified I do not consider the base object to be const-ref.
//
// Note that the get-*-value primitives may return a reference if the
// field is a reference.
if (LHS->isRef()) {
if (!inferConstRef(LHS->symbol())) {
return false;
}
}
}
default:
break;
}
return isSafeRefPrimitive(use);
}
static bool inferRefToConst(Symbol* sym) {
INT_ASSERT(sym->isRef());
bool isConstRef = sym->qualType().getQual() == QUAL_CONST_REF;
const bool wasRefToConst = sym->hasFlag(FLAG_REF_TO_CONST);
ConstInfo* info = infoMap[sym];
// If this ref isn't const, then it can't point to a const thing
if (info == NULL) {
return false;
} else if (info->finalizedRefToConst || wasRefToConst || !isConstRef) {
return wasRefToConst;
}
bool isFirstCall = false;
if (info->alreadyCalled == false) {
isFirstCall = true;
info->alreadyCalled = true;
}
bool isRefToConst = true;
if (isArgSymbol(sym)) {
// Check each call and set isRefToConst to false if any actual is not a ref
// to a const.
FnSymbol* fn = toFnSymbol(sym->defPoint->parentSymbol);
if (fn->hasFlag(FLAG_VIRTUAL) ||
fn->hasFlag(FLAG_EXPORT) ||
fn->hasFlag(FLAG_EXTERN)) {
// Not sure how to best handle virtual calls, so simply set false for now
//
// For export or extern functions, return false because we don't have
// all the information about how the function is called.
isRefToConst = false;
} else {
// Need this part to be re-entrant in case of recursive functions
while (info->fnUses != NULL && isRefToConst) {
SymExpr* se = info->fnUses;
info->fnUses = se->symbolSymExprsNext;
CallExpr* call = toCallExpr(se->parentExpr);
INT_ASSERT(call && call->isResolved());
Symbol* actual = toSymExpr(formal_to_actual(call, sym))->symbol();
if (actual->isRef()) {
// I don't think we technically need to skip if the actual is the
// same symbol as the formal, but it makes things simpler.
if (actual != sym && !inferRefToConst(actual)) {
isRefToConst = false;
}
} else {
// Passing a non-ref actual to a reference formal is currently
// considered to be the same as an addr-of
if (actual->qualType().getQual() != QUAL_CONST_VAL) {
isRefToConst = false;
}
}
}
}
}
while (info->hasMore() && isRefToConst) {
SymExpr* use = info->next();
CallExpr* call = toCallExpr(use->parentExpr);
if (call == NULL) continue;
if (isMoveOrAssign(call)) {
if (use == call->get(1)) {
if (SymExpr* se = toSymExpr(call->get(2))) {
if (se->isRef() && !inferRefToConst(se->symbol())) {
isRefToConst = false;
}
}
else {
CallExpr* RHS = toCallExpr(call->get(2));
INT_ASSERT(RHS);
if (RHS->isPrimitive(PRIM_ADDR_OF) ||
RHS->isPrimitive(PRIM_SET_REFERENCE)) {
SymExpr* src = toSymExpr(RHS->get(1));
if (src->isRef()) {
if (!inferRefToConst(src->symbol())) {
isRefToConst = false;
}
} else {
if (src->symbol()->qualType().getQual() != QUAL_CONST_VAL) {
isRefToConst = false;
}
}
} else {
isRefToConst = false;
}
}
}
}
else if (call->isResolved()) {
isRefToConst = true;
}
else {
isRefToConst = isSafeRefPrimitive(use);
}
}
if (isFirstCall) {
if (isRefToConst) {
INT_ASSERT(info->finalizedRefToConst == false);
sym->addFlag(FLAG_REF_TO_CONST);
}
info->reset();
info->finalizedRefToConst = true;
} else if (!isRefToConst) {
info->finalizedRefToConst = true;
}
return isRefToConst;
}
