Re: [PATCH 5/8] coroutines: Define and populate accessors for debug state.

[Jason Merrill via Gcc-patches]

On 9/1/21 6:54 AM, Iain Sandoe wrote:

This is an efficiency measure and repeats the pattern used for
other identifiers used in the coroutine implementation.

In support of debugging, the user might well need to look at some
of the variables that the implementation manipulates in lowering
the coroutines.  The defines the identifiers for these and populates
them on demand (avoiding repeated identifier calls).

Contributory to debug support (PR 99215)

Signed-off-by: Iain Sandoe <i...@sandoe.co.uk>

gcc/cp/ChangeLog:

        * coroutines.cc: Add identifiers for implementation
        variables that we want to expose to debug.
        (coro_init_identifiers): Initialize implementation names.
        (coro_promise_type_found_p): Use pre-built identifiers.
        (build_actor_fn): Likewise.
        (build_destroy_fn): Likewise.
---
  gcc/cp/coroutines.cc | 32 ++++++++++++++++++++++++--------
  1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 081e1a46c63..3b46aac4dc5 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -215,7 +215,17 @@ static GTY(()) tree coro_await_ready_identifier;
  static GTY(()) tree coro_await_suspend_identifier;
  static GTY(()) tree coro_await_resume_identifier;
  
-/* Create the identifiers used by the coroutines library interfaces.  */
+/* Accessors for the coroutine frame state used by the implementation.  */
+
+static GTY(()) tree coro_resume_fn_field;
+static GTY(()) tree coro_destroy_fn_field;
+static GTY(()) tree coro_promise_field;
+static GTY(()) tree coro_frame_needs_free_field;
+static GTY(()) tree coro_resume_index_field;
+static GTY(()) tree coro_self_handle_field;

Since these are identifiers, not FIELD_DECLs, calling them *_field seems 
misleading.

+/* Create the identifiers used by the coroutines library interfaces and
+   the implementation frame state.  */
  
  static void
  coro_init_identifiers ()
@@ -241,6 +251,14 @@ coro_init_identifiers ()
    coro_await_ready_identifier = get_identifier ("await_ready");
    coro_await_suspend_identifier = get_identifier ("await_suspend");
    coro_await_resume_identifier = get_identifier ("await_resume");
+
+  /* Coroutine state frame field accessors.  */
+  coro_resume_fn_field = get_identifier ("_Coro_resume_fn");
+  coro_destroy_fn_field = get_identifier ("_Coro_destroy_fn");
+  coro_promise_field = get_identifier ("_Coro_promise");
+  coro_frame_needs_free_field = get_identifier ("_Coro_frame_needs_free");
+  coro_resume_index_field = get_identifier ("_Coro_resume_index");
+  coro_self_handle_field = get_identifier ("_Coro_self_handle");
  }
  
  /* Trees we only need to set up once.  */
@@ -513,12 +531,12 @@ coro_promise_type_found_p (tree fndecl, location_t loc)
        /* Build a proxy for a handle to "self" as the param to
         await_suspend() calls.  */
        coro_info->self_h_proxy
-       = build_lang_decl (VAR_DECL, get_identifier ("_Coro_self_handle"),
+       = build_lang_decl (VAR_DECL, coro_self_handle_field,
                           coro_info->handle_type);
  
        /* Build a proxy for the promise so that we can perform lookups.  */
        coro_info->promise_proxy
-       = build_lang_decl (VAR_DECL, get_identifier ("_Coro_promise"),
+       = build_lang_decl (VAR_DECL, coro_promise_field,
                           coro_info->promise_type);
  
        /* Note where we first saw a coroutine keyword.  */
@@ -2198,8 +2216,7 @@ build_actor_fn (location_t loc, tree coro_frame_type, 
tree actor, tree fnbody,
      = {actor, actor_frame, coro_frame_type, loc, local_var_uses};
    cp_walk_tree (&fnbody, transform_local_var_uses, &xform_vars_data, NULL);
  
-  tree resume_idx_name = get_identifier ("_Coro_resume_index");
-  tree rat_field = lookup_member (coro_frame_type, resume_idx_name, 1, 0,
+  tree rat_field = lookup_member (coro_frame_type, coro_resume_index_field, 1, 
0,
                                  tf_warning_or_error);
    tree rat = build3 (COMPONENT_REF, short_unsigned_type_node, actor_frame,
                     rat_field, NULL_TREE);
@@ -2462,7 +2479,7 @@ build_actor_fn (location_t loc, tree coro_frame_type, 
tree actor, tree fnbody,
  
    /* We will need to know which resume point number should be encoded.  */
    tree res_idx_m
-    = lookup_member (coro_frame_type, resume_idx_name,
+    = lookup_member (coro_frame_type, coro_resume_index_field,
                     /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
    tree resume_pt_number
      = build_class_member_access_expr (actor_frame, res_idx_m, NULL_TREE, 
false,
@@ -2504,8 +2521,7 @@ build_destroy_fn (location_t loc, tree coro_frame_type, 
tree destroy,
  
    tree destr_frame = build1 (INDIRECT_REF, coro_frame_type, destr_fp);
  
-  tree resume_idx_name = get_identifier ("_Coro_resume_index");
-  tree rat_field = lookup_member (coro_frame_type, resume_idx_name, 1, 0,
+  tree rat_field = lookup_member (coro_frame_type, coro_resume_index_field, 1, 
0,
                                  tf_warning_or_error);
    tree rat = build3 (COMPONENT_REF, short_unsigned_type_node, destr_frame,
                     rat_field, NULL_TREE);