> But in theory this pessimizes code as aggregate_value_p returned true
> for this? That is, isn't the bug that we rewrite a possible
> return-slot-decl into SSA? (do we do that here?)
Yes, aggregate_value_p returns true for this because the ABI says that this
type is returned in memory. And, no, I don't think that this will further
pessimize, given that it's already "pessimized" in gimplify_modify_expr_rhs:
case CALL_EXPR:
/* For calls that return in memory, give *to_p as the CALL_EXPR's
return slot so that we don't generate a temporary. */
if (!CALL_EXPR_RETURN_SLOT_OPT (*from_p)
&& aggregate_value_p (*from_p, *from_p))
{
bool use_target;
if (!(rhs_predicate_for (*to_p))(*from_p))
/* If we need a temporary, *to_p isn't accurate. */
use_target = false;
/* It's OK to use the return slot directly unless it's an NRV. */
else if (TREE_CODE (*to_p) == RESULT_DECL
&& DECL_NAME (*to_p) == NULL_TREE
&& needs_to_live_in_memory (*to_p))
use_target = true;
else if (is_gimple_reg_type (TREE_TYPE (*to_p))
|| (DECL_P (*to_p) && DECL_REGISTER (*to_p)))
/* Don't force regs into memory. */
use_target = false;
--
Eric Botcazou
