On 5/13/20 9:26 AM, Iain Sandoe wrote:
Nathan Sidwell <nat...@acm.org> wrote:
On 5/13/20 6:59 AM, Iain Sandoe wrote:
@@ -1045,25 +1044,50 @@ finish_co_return_stmt (location_t kw, tree expr)
if (!crv_meth || crv_meth == error_mark_node)
return error_mark_node;
- vec<tree, va_gc> *args = make_tree_vector_single (expr);
- co_ret_call = build_new_method_call (
- get_coroutine_promise_proxy (current_function_decl), crv_meth,
&args,
- NULL_TREE, LOOKUP_NORMAL, NULL, tf_warning_or_error);
+ /* [class.copy.elision] / 3.
+ An implicitly movable entity is a variable of automatic storage
+ duration that is either a non-volatile object or an rvalue
reference
+ to a non-volatile object type. For such objects in the context of
+ the co_return, the overload resolution should be carried out first
+ treating the object as an rvalue, if that fails, then we fall back
+ to regular overload resolution. */
+ tree obj = STRIP_NOPS (expr);
+ if (TREE_TYPE (obj)
+ && TYPE_REF_P (TREE_TYPE (obj))
+ && TYPE_REF_IS_RVALUE (TREE_TYPE (obj)))
+ obj = TREE_OPERAND (obj, 0);
+
+ if (TREE_CODE (obj) == PARM_DECL
+ || (VAR_P (obj)
+ && decl_storage_duration (obj) == dk_auto
+ && !TYPE_VOLATILE (TREE_TYPE (obj))))
this is wrong and insufficient. As I explained on IRC -- 'expressions
of reference type are not a thing'. We always bash them into an
indirect-ref of the referency thing.
Look at check_return_value and how it handles NRVO. There's a
treat_lvalue_as_rvalue_p call that I'll bet you can use[*], along with
a move wrapper, which maybe what you want rather than the below rvalue
(expr).
a return_expr's operand is an INIT_EXPR or MODIFY_EXPR whose LHS is
DECL_RESULT(fn). So that's almost what you want here. I think the
general form is
if (treat_lval_as_rval ())
{ silently try callexpr with moved operand }
if no joy either way
{ noisily try callexpr with unmoved operand }
[*] That is insufficient, because elision also applies to objects
you've placed into the coro frame. by the std those are still
automatic storage objects, but inside the compiler they are of course
COMPONENT_REFs (or do you cons up VAR_DECLS of reference type that
refer to them?). Further, the PARM_DECL case can;t occur here -- the
actor fn's only parm is the coro frame pointer.
This is the equivalent of finish_return_stmt () in the parser, it knows
nothing of the eventual morphing of local vars (or parms) into frame
references.
So I only need to handle what can be returned by "expr =
cp_parser_expression (parser);”
dependent expressions are dealt with above, with an early return with
“type_unknown_node”.
So, it might be I can just reuse the code you point to?
Yeah I think so. I realized it was pre-xform so the component-ref stuff
was irrelevant when out shopping. In other news, flour's back in stock :)
nathan
--
Nathan Sidwell
