// This routine returns true if the value of the given symbol may have changed
// due to execution of the containing expression.
// If the symbol is a reference, this means that the address to which the
// symbol points will be changed, not the value contained in that address. See
// isRefUse() for that case.
// To be conservative, the routine should return true by default and then
// select the cases where we are sure nothing has changed.
static bool needsKilling(SymExpr* se, std::set<Symbol*>& liveRefs)
{
INT_ASSERT(se->isRef() == false);
if (toGotoStmt(se->parentExpr)) {
return false;
}
if (toCondStmt(se->parentExpr)) {
return false;
}
if (toBlockStmt(se->parentExpr)) {
return false;
}
if (isDefExpr(se->parentExpr)) {
return false;
}
CallExpr* call = toCallExpr(se->parentExpr);
if (FnSymbol* fn = call->resolvedFunction())
{
// Skip the "base" symbol.
if (se->symbol() == fn)
{
return false;
}
ArgSymbol* arg = actual_to_formal(se);
if (arg->intent == INTENT_OUT ||
arg->intent == INTENT_INOUT ||
arg->intent == INTENT_REF ||
arg->hasFlag(FLAG_ARG_THIS)) // Todo: replace with arg intent check?
{
liveRefs.insert(se->symbol());
return true;
}
if (isRecordWrappedType(arg->type))
{
return true;
}
return false;
}
else
{
const bool isFirstActual = call->get(1) == se;
if ((call->isPrimitive(PRIM_MOVE) || call->isPrimitive(PRIM_ASSIGN))
&& isFirstActual)
{
return true;
}
if (isOpEqualPrim(call) && isFirstActual)
{
return true;
}
if (call->isPrimitive(PRIM_SET_MEMBER) && isFirstActual)
{
return true;
}
if (call->isPrimitive(PRIM_ARRAY_SET) ||
call->isPrimitive(PRIM_ARRAY_SET_FIRST))
{
if (isFirstActual)
{
return true;
}
return false;
}
if (call->isPrimitive(PRIM_GET_MEMBER))
{
// This creates an alias to a portion of the first arg.
// We could track this as a reference and invalidate a pair containing
// this symbol when the ref is dereferenced. But for now, we want to
// preserve the mapping ref = &value in the RefMap, so having a (ref,
// value) pair also possibly mean ref = &(value.subfield) does not quite
// fit.
// We could keep the ability to do (deref ref) <- value substitution by
// keeping a separate map for "true" references, or by performing those
// substitutions in a separate pass.
// For now, we treat subfield extraction as evidence of a future change
// to the symbol itself, and use that fact to remove it from
// consideration in copy propagation.
if (isFirstActual)
{
// We select just the case where the referent is passed by value,
// because in the other case, the address of the object is not
// returned, so that means that the address (i.e. the value of the
// reference variable) does not change.
return true;
}
return false;
}
if (call->isPrimitive(PRIM_ADDR_OF) ||
call->isPrimitive(PRIM_SET_REFERENCE)) {
liveRefs.insert(se->symbol());
return true;
}
return false;
}
INT_ASSERT(0); // Should never get here.
return true;
}
// Returns true if the symbol is read in the containing expression,
// false otherwise. If the operand is used as an address,
// that does not count as a 'read', so false is returned in that case.
static bool isUse(SymExpr* se)
{
if (toGotoStmt(se->parentExpr))
{
return false;
}
if (toCondStmt(se->parentExpr))
{
return true;
}
if (toBlockStmt(se->parentExpr))
{
return true;
}
if (isDefExpr(se->parentExpr))
{
return false;
}
CallExpr* call = toCallExpr(se->parentExpr);
if (FnSymbol* fn = call->resolvedFunction())
{
// Skip the "base" symbol.
if (se->symbol() == fn)
{
return false;
}
// A "normal" call.
ArgSymbol* arg = actual_to_formal(se);
if (arg->intent == INTENT_OUT ||
arg->intent == INTENT_REF)
{
return false;
} else if (arg->intent == INTENT_CONST_REF &&
isRecord(arg->type)) {
// We can currently return a const reference to a field in a record
// passed by const ref.
return false;
}
}
else
{
INT_ASSERT(call->primitive);
const bool isFirstActual = call->get(1) == se;
switch(call->primitive->tag)
{
default:
return true;
case PRIM_MOVE:
case PRIM_ASSIGN:
case PRIM_ADD_ASSIGN:
case PRIM_SUBTRACT_ASSIGN:
case PRIM_MULT_ASSIGN:
case PRIM_DIV_ASSIGN:
case PRIM_MOD_ASSIGN:
case PRIM_LSH_ASSIGN:
case PRIM_RSH_ASSIGN:
case PRIM_AND_ASSIGN:
case PRIM_OR_ASSIGN:
case PRIM_XOR_ASSIGN:
if (isFirstActual)
{
return false;
}
return true;
case PRIM_ARRAY_ALLOC:
case PRIM_ADDR_OF:
case PRIM_SET_REFERENCE:
return false; // See Note #2.
case PRIM_PRIVATE_BROADCAST:
// The operand is used by name (it must be a manifest constant).
// Thus it acts more like an address than a value.
return false;
case PRIM_CHPL_COMM_GET:
case PRIM_CHPL_COMM_PUT:
case PRIM_CHPL_COMM_ARRAY_GET:
case PRIM_CHPL_COMM_ARRAY_PUT:
case PRIM_CHPL_COMM_GET_STRD:
case PRIM_CHPL_COMM_PUT_STRD:
// ('comm_get/put' locAddr locale widePtr len)
// The first and third operands are treated as addresses.
// The second and fourth are values
if (se == call->get(2) || se == call->get(4))
{
return true;
}
return false;
case PRIM_CHPL_COMM_REMOTE_PREFETCH:
// comm prefetch locale widePtr len
// second argument is an address
// first and third are values.
if (isFirstActual || se == call->get(3))
{
return true;
}
return false;
case PRIM_SET_MEMBER:
// The first operand works like a reference, and the second is a field
// name. Only the third is a replaceable use.
if (se == call->get(3))
{
return true;
}
return false;
case PRIM_GET_MEMBER:
case PRIM_GET_MEMBER_VALUE:
if (isFirstActual)
{
return false;
}
return true;
case PRIM_ARRAY_SET:
case PRIM_ARRAY_SET_FIRST:
case PRIM_ARRAY_GET:
case PRIM_ARRAY_GET_VALUE:
// The first operand is treated like a reference.
if (isFirstActual)
{
return false;
}
return true;
case PRIM_SET_UNION_ID:
// The first operand is treated like a reference.
if (isFirstActual)
{
return false;
}
return true;
}
}
return true;
}
