c++: don't call 'rvalue' in coroutines code

A change to check glvalue_p rather than specifically for TARGET_EXPR
revealed issues with the coroutines code's use of the 'rvalue' function,
which shouldn't be used on class glvalues, so I've removed those calls.

In build_co_await I just dropped them, because I don't see anything in the
co_await specification that indicates that we would want to move from an
lvalue result of operator co_await.  And simplified that code while I was
touching it; cp_build_modify_expr (...INIT_EXPR...) will call the
constructor.

In morph_fn_to_coro I changed the handling of the rvalue reference coroutine
frame field to use move, to treat the rval ref as an xvalue.  I used
forward_parm to pass the function parms to the constructor for the field.
And I simplified the return handling so we get the desired rvalue semantics
from the normal implicit move on return.

I question default-initializing the non-void return value of the function if
get_return_object returns void; I'm not messing with it here, but I've filed
PR100476 about it.

gcc/cp/ChangeLog:

	* coroutines.cc (build_co_await): Don't call 'rvalue'.
	(flatten_await_stmt): Simplify initialization.
	(morph_fn_to_coro): Change 'rvalue' to 'move'.  Simplify.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C:
	Adjust diagnostic.

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index dbd703a..7166206 100644 (file)
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -950,18 +950,11 @@ build_co_await (location_t loc, tree a, suspend_point_kind suspend_kind)
       e_proxy = o;
       o = NULL_TREE; /* The var is already present.  */
     }
-  else if (type_build_ctor_call (o_type))
-    {
-      e_proxy = get_awaitable_var (suspend_kind, o_type);
-      releasing_vec arg (make_tree_vector_single (rvalue (o)));
-      o = build_special_member_call (e_proxy, complete_ctor_identifier,
-                                    &arg, o_type, LOOKUP_NORMAL,
-                                    tf_warning_or_error);
-    }
   else
     {
       e_proxy = get_awaitable_var (suspend_kind, o_type);
-      o = build2 (INIT_EXPR, o_type, e_proxy, rvalue (o));
+      o = cp_build_modify_expr (loc, e_proxy, INIT_EXPR, o,
+                               tf_warning_or_error);
     }
 
   /* I suppose we could check that this is contextually convertible to bool.  */
@@ -2989,15 +2982,8 @@ flatten_await_stmt (var_nest_node *n, hash_set<tree> *promoted,
          gcc_checking_assert (!already_present);
          tree inner = TREE_OPERAND (init, 1);
          gcc_checking_assert (TREE_CODE (inner) != COND_EXPR);
-         if (type_build_ctor_call (var_type))
-           {
-             releasing_vec p_in (make_tree_vector_single (init));
-             init = build_special_member_call (var, complete_ctor_identifier,
-                                               &p_in, var_type, LOOKUP_NORMAL,
-                                               tf_warning_or_error);
-           }
-         else
-           init = build2 (INIT_EXPR, var_type, var, init);
+         init = cp_build_modify_expr (input_location, var, INIT_EXPR, init,
+                                      tf_warning_or_error);
          /* Simplify for the case that we have an init containing the temp
             alone.  */
          if (t == n->init && n->var == NULL_TREE)
@@ -4862,43 +4848,19 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
              vec_safe_push (promise_args, this_ref);
            }
          else if (parm.rv_ref)
-           vec_safe_push (promise_args, rvalue(fld_idx));
+           vec_safe_push (promise_args, move (fld_idx));
          else
            vec_safe_push (promise_args, fld_idx);
 
          if (parm.rv_ref || parm.pt_ref)
            /* Initialise the frame reference field directly.  */
-           r = build_modify_expr (fn_start, TREE_OPERAND (fld_idx, 0),
-                                  parm.frame_type, INIT_EXPR,
-                                  DECL_SOURCE_LOCATION (arg), arg,
-                                  DECL_ARG_TYPE (arg));
-         else if (type_build_ctor_call (parm.frame_type))
-           {
-             vec<tree, va_gc> *p_in;
-             if (CLASS_TYPE_P (parm.frame_type)
-                 && classtype_has_non_deleted_move_ctor (parm.frame_type))
-               p_in = make_tree_vector_single (move (arg));
-             else if (lvalue_p (arg))
-               p_in = make_tree_vector_single (rvalue (arg));
-             else
-               p_in = make_tree_vector_single (arg);
-             /* Construct in place or move as relevant.  */
-             r = build_special_member_call (fld_idx, complete_ctor_identifier,
-                                            &p_in, parm.frame_type,
-                                            LOOKUP_NORMAL,
-                                            tf_warning_or_error);
-             release_tree_vector (p_in);
-           }
+           r = cp_build_modify_expr (fn_start, TREE_OPERAND (fld_idx, 0),
+                                     INIT_EXPR, arg, tf_warning_or_error);
          else
            {
-             if (!same_type_p (parm.frame_type, DECL_ARG_TYPE (arg)))
-               r = build1_loc (DECL_SOURCE_LOCATION (arg), CONVERT_EXPR,
-                               parm.frame_type, arg);
-             else
-               r = arg;
-             r = build_modify_expr (fn_start, fld_idx, parm.frame_type,
-                                    INIT_EXPR, DECL_SOURCE_LOCATION (arg), r,
-                                    TREE_TYPE (r));
+             r = forward_parm (arg);
+             r = cp_build_modify_expr (fn_start, fld_idx, INIT_EXPR, r,
+                                       tf_warning_or_error);
            }
          finish_expr_stmt (r);
          if (!parm.trivial_dtor)
@@ -5044,16 +5006,8 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
       DECL_IGNORED_P (gro) = true;
       add_decl_expr (gro);
       gro_bind_vars = gro;
-      if (type_build_ctor_call (gro_type))
-       {
-         vec<tree, va_gc> *arg = make_tree_vector_single (get_ro);
-         r = build_special_member_call (gro, complete_ctor_identifier,
-                                        &arg, gro_type, LOOKUP_NORMAL,
-                                        tf_warning_or_error);
-         release_tree_vector (arg);
-       }
-      else
-       r = build2_loc (fn_start, INIT_EXPR, gro_type, gro, get_ro);
+      r = cp_build_modify_expr (input_location, gro, INIT_EXPR, get_ro,
+                               tf_warning_or_error);
       /* The constructed object might require a cleanup.  */
       if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (gro_type))
        {
@@ -5111,37 +5065,26 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
 
   if (same_type_p (gro_type, fn_return_type))
     r = gro_is_void_p ? NULL_TREE : DECL_RESULT (orig);
+  else if (!gro_is_void_p)
+    /* check_return_expr will automatically return gro as an rvalue via
+       treat_lvalue_as_rvalue_p.  */
+    r = gro;
+  else if (CLASS_TYPE_P (fn_return_type))
+    {
+      /* For class type return objects, we can attempt to construct,
+        even if the gro is void. ??? Citation ??? c++/100476  */
+      r = build_special_member_call (NULL_TREE,
+                                    complete_ctor_identifier, NULL,
+                                    fn_return_type, LOOKUP_NORMAL,
+                                    tf_warning_or_error);
+      r = build_cplus_new (fn_return_type, r, tf_warning_or_error);
+    }
   else
     {
-      if (CLASS_TYPE_P (fn_return_type))
-       {
-         /* For class type return objects, we can attempt to construct,
-            even if the gro is void.  */
-         vec<tree, va_gc> *args = NULL;
-         vec<tree, va_gc> **arglist = NULL;
-         if (!gro_is_void_p)
-           {
-             args = make_tree_vector_single (rvalue (gro));
-             arglist = &args;
-           }
-         r = build_special_member_call (NULL_TREE,
-                                        complete_ctor_identifier, arglist,
-                                        fn_return_type, LOOKUP_NORMAL,
-                                        tf_warning_or_error);
-         r = build_cplus_new (fn_return_type, r, tf_warning_or_error);
-         if (args)
-           release_tree_vector (args);
-       }
-      else if (gro_is_void_p)
-       {
-         /* We can't initialize a non-class return value from void.  */
-         error_at (input_location, "cannot initialize a return object of type"
-                   " %qT with an rvalue of type %<void%>", fn_return_type);
-         r = error_mark_node;
-       }
-      else
-       r = build1_loc (input_location, CONVERT_EXPR,
-                       fn_return_type, rvalue (gro));
+      /* We can't initialize a non-class return value from void.  */
+      error_at (input_location, "cannot initialize a return object of type"
+               " %qT with an rvalue of type %<void%>", fn_return_type);
+      r = error_mark_node;
     }
 
   finish_return_stmt (r);

diff --git a/gcc/testsuite/g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C b/gcc/testsuite/g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C
index f9e8a5f..0512f03 100644 (file)
--- a/gcc/testsuite/g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C
+++ b/gcc/testsuite/g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C
@@ -37,7 +37,7 @@ my_coro (std::coroutine_handle<>& h)
 {
   PRINT ("coro1: about to return");
   co_return;
-} // { dg-error {'struct Thing' used where a 'int' was expected} }
+} // { dg-error {cannot convert 'Thing' to 'int' in return} }
 
 int main ()
 {