c++, coroutines: Simplify initial_await_resume_called.

We do not need to generate this code early, since it does not affect
any of the analysis.  Lowering it later takes less code, and avoids
modifying the initial await expresssion which will simplify changes
to analysis to deal with open PRs.

gcc/cp/ChangeLog:

	* coroutines.cc (expand_one_await_expression): Set the
	initial_await_resume_called flag here.
	(build_actor_fn): Populate the frame accessor for the
	initial_await_resume_called flag.
	(cp_coroutine_transform::wrap_original_function_body): Do
	not modify the initial_await expression to include the
	initial_await_resume_called flag here.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
(cherry picked from commit bfd4aae0a999375cf008b75c14607c7b94daced3)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index c1eaf0ebb1229fa7613a27aa77abb1e8ca4095ab..deaf32a9398b9be8e1bd96df138ea76ad68ac662 100644 (file)
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -2042,8 +2042,10 @@ expand_one_await_expression (tree *expr, tree *await_expr, void *d)
   tree awaiter_calls = TREE_OPERAND (saved_co_await, 3);
 
   tree source = TREE_OPERAND (saved_co_await, 4);
-  bool is_final = (source
-                  && TREE_INT_CST_LOW (source) == (int) FINAL_SUSPEND_POINT);
+  bool is_final
+    = (source && TREE_INT_CST_LOW (source) == (int) FINAL_SUSPEND_POINT);
+  bool is_initial
+    = (source && TREE_INT_CST_LOW (source) == (int) INITIAL_SUSPEND_POINT);
 
   /* Build labels for the destinations of the control flow when we are resuming
      or destroying.  */
@@ -2171,6 +2173,13 @@ expand_one_await_expression (tree *expr, tree *await_expr, void *d)
   /* Resume point.  */
   add_stmt (build_stmt (loc, LABEL_EXPR, resume_label));
 
+  if (is_initial && data->i_a_r_c)
+    {
+      r = cp_build_modify_expr (loc, data->i_a_r_c, NOP_EXPR, boolean_true_node,
+                               tf_warning_or_error);
+      finish_expr_stmt (r);
+    }
+
   /* This will produce the value (if one is provided) from the co_await
      expression.  */
   tree resume_call = TREE_VEC_ELT (awaiter_calls, 2); /* await_resume().  */
@@ -2671,8 +2680,12 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
 
   /* We've now rewritten the tree and added the initial and final
      co_awaits.  Now pass over the tree and expand the co_awaits.  */
+  tree i_a_r_c = NULL_TREE;
+  if (flag_exceptions)
+    i_a_r_c = coro_build_frame_access_expr (actor_frame, coro_frame_i_a_r_c_id,
+                                          false, tf_warning_or_error);
 
-  coro_aw_data data = {actor, actor_fp, resume_idx_var, NULL_TREE,
+  coro_aw_data data = {actor, actor_fp, resume_idx_var, i_a_r_c,
                       ash, del_promise_label, ret_label,
                       continue_label, restart_dispatch_label, continuation, 2};
   cp_walk_tree (&actor_body, await_statement_expander, &data, NULL);
@@ -4452,30 +4465,6 @@ cp_coroutine_transform::wrap_original_function_body ()
       tree tcb = build_stmt (loc, TRY_BLOCK, NULL_TREE, NULL_TREE);
       add_stmt (tcb);
       TRY_STMTS (tcb) = push_stmt_list ();
-      if (initial_await != error_mark_node)
-       {
-         /* Build a compound expression that sets the
-            initial-await-resume-called variable true and then calls the
-            initial suspend expression await resume.
-            In the case that the user decides to make the initial await
-            await_resume() return a value, we need to discard it and, it is
-            a reference type, look past the indirection.  */
-         if (INDIRECT_REF_P (initial_await))
-           initial_await = TREE_OPERAND (initial_await, 0);
-         /* In the case that the initial_await returns a target expression
-            we might need to look through that to update the await expr.  */
-         tree iaw = initial_await;
-         if (TREE_CODE (iaw) == TARGET_EXPR)
-           iaw = TARGET_EXPR_INITIAL (iaw);
-         gcc_checking_assert (TREE_CODE (iaw) == CO_AWAIT_EXPR);
-         tree vec = TREE_OPERAND (iaw, 3);
-         tree aw_r = TREE_VEC_ELT (vec, 2);
-         aw_r = convert_to_void (aw_r, ICV_STATEMENT, tf_warning_or_error);
-         tree update = build2 (MODIFY_EXPR, boolean_type_node, i_a_r_c,
-                               boolean_true_node);
-         aw_r = cp_build_compound_expr (update, aw_r, tf_warning_or_error);
-         TREE_VEC_ELT (vec, 2) = aw_r;
-       }
       /* Add the initial await to the start of the user-authored function.  */
       finish_expr_stmt (initial_await);
       /* Append the original function body.  */