Re: [PATCH 6/8] coroutines: Convert implementation variables to debug-friendly form.

[Jason Merrill <jason@redhat.com>]

On 9/5/21 3:47 PM, Iain Sandoe wrote:
> Hello Jason,
> 
> The patch below is a squashed version of:
> 
> (approved) [PATCH 4/8] coroutines: Make some of the artificial names more  debugger-friendly.
>                    [PATCH 5/8] coroutines: Define and populate accessors for debug  state.
>                    [PATCH 6/8] coroutines: Convert implementation variables to  debug-friendly form.
> (approved) [PATCH 8/8] coroutines: Make the continue handle visible to debug.
> 
> 
> [PATCH 6/8] coroutines: Convert implementation variables to debug-friendly form.
> 
>> On 3 Sep 2021, at 15:21, Iain Sandoe <iain@sandoe.co.uk> wrote:
>>> On 3 Sep 2021, at 15:12, Jason Merrill <jason@redhat.com> wrote:
>>>
>>> On 9/3/21 9:56 AM, Iain Sandoe wrote:
>>>>> On 3 Sep 2021, at 14:52, Jason Merrill <jason@redhat.com> wrote:
>>>>>
>>>>> On 9/1/21 6:55 AM, Iain Sandoe wrote:
> 
>>>>>> 	(morph_fn_to_coro): Likewise.
>>>>>
>>>>> Hmm, this patch doesn't seem to match the description and ChangeLog entry other than in the names of the functions changed.
>>>> with 20:20 hindsight I should have squashed the (several) patches related to the implementation symbols,
>>>> I’ll redo the description - essentially, this is just making use of the simplification available because we now have pre-defined values for the field names.
>>>
>>> I can see how that describes a few lines in this patch, but not for instance the change to transform_await_expr, which seems to have nothing to do with names?
>>
>> it’s indirect indeed - but the changes we’ve made to the variable handling mean that we no longer need to rewrite the
>> proxy vars into their frame->offset; that is handled by the DECL_VALUE_EXPR (as for user’s vars ) - the change to transform_await_expr is removing the now defunct substitution (and poorly described, sorry).
> 
> now stated explicitly in the comments and in the commit log.

So that sounds like it goes with patch 1, rather than 4/5?  But it's 
fine as is.

>>> But yes, moving the changed lines that just use the variables from the previous patch into that commit sounds good.  I use rebase -i for that sort of thing all the time.
>>
>> yeah, me too -  I realised too late that this series could have had more squashing - if it would make things easier I could do that for the patches related to implemenation variables .. - which would include patch 8 (but not patch 7 which is related to parms only)
> 
> squashing the series should make the changes clearer.
> 
> [PATCH 5/8] coroutines: Define and populate accessors for debug  state.
> 
>>>>> +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.
>>> I could append _id or _name .. they were just getting long already.
>>> (they are names of fields, so that would not be misleading)
>>
>> _id works for me, either with or without the _field.
>>
> 
> Done
> 
> OK now?

OK, thanks.

> thanks
> Iain
> 
> ======
> 
> [PATCH] coroutines: Expose implementation state to the debugger.
> 
> In the process of transforming a coroutine into the separate representation
> as the ramp function and a state machine, we generate some variables that
> are of interest to a user during debugging.  Any variable that is persistent
> for the execution of the coroutine is placed into the coroutine frame.
> 
> In particular:
>    The promise object.
>    The function pointers for the resumer and destroyer.
>    The current resume index (suspend point).
>    The handle that represents this coroutine 'self handle'.
>    Any handle provided for a continuation coroutine.
>    Whether the coroutine frame is allocated and needs to be freed.
> 
> Visibility of some of these has already been requested by end users.
> 
> This patch ensures that such variables have names that are usable in a
> debugger, but are in the reserved namespace for the implementation (they
> all begin with _Coro_).  The identifiers are generated lazily when the
> first coroutine is encountered.
> 
> We place the variables into the outermost bind expression and then add a
> DECL_VALUE_EXPR to each that points to the frame entry.
> 
> These changes simplify the handling of the variables in the body of the
> function (in particular, the use of the DECL_VALUE_EXPR means that we now
> no longer need to rewrite proxies for the promise and coroutine handles into
> the frame->offset form).
> 
> Partial improvement to debugging (PR c++/99215).
> 
> Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
> 
> gcc/cp/ChangeLog:
> 
> 	* coroutines.cc (coro_resume_fn_id, coro_destroy_fn_id,
> 	coro_promise_id, coro_frame_needs_free_id, coro_resume_index_id,
> 	coro_self_handle_id, coro_actor_continue_id,
> 	coro_frame_i_a_r_c_id): New.
> 	(coro_init_identifiers): Initialize new name identifiers.
> 	(coro_promise_type_found_p): Use pre-built identifiers.
> 	(struct await_xform_data): Remove unused fields.
> 	(transform_await_expr): Delete code that is now unused.
> 	(build_actor_fn): Simplify interface, use pre-built identifiers and
> 	remove transforms that are no longer needed.
> 	(build_destroy_fn): Use revised field names.
> 	(register_local_var_uses): Use pre-built identifiers.
> 	(coro_rewrite_function_body): Simplify interface, use pre-built
> 	identifiers.  Generate proxy vars in the outer bind expr scope for the
> 	implementation state that we wish to expose.
> 	(morph_fn_to_coro): Adjust comments for new variable names, use pre-
> 	built identifiers.  Remove unused code to generate frame entries for
> 	the implementation state.  Adjust call for build_actor_fn.
> ---
>   gcc/cp/coroutines.cc | 285 +++++++++++++++++++++----------------------
>   1 file changed, 137 insertions(+), 148 deletions(-)
> 
> diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
> index 9ab2be04266..cd774b78ae0 100644
> --- a/gcc/cp/coroutines.cc
> +++ b/gcc/cp/coroutines.cc
> @@ -215,7 +215,19 @@ 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_id;
> +static GTY(()) tree coro_destroy_fn_id;
> +static GTY(()) tree coro_promise_id;
> +static GTY(()) tree coro_frame_needs_free_id;
> +static GTY(()) tree coro_resume_index_id;
> +static GTY(()) tree coro_self_handle_id;
> +static GTY(()) tree coro_actor_continue_id;
> +static GTY(()) tree coro_frame_i_a_r_c_id;
> +
> +/* Create the identifiers used by the coroutines library interfaces and
> +   the implementation frame state.  */
>   
>   static void
>   coro_init_identifiers ()
> @@ -241,6 +253,16 @@ 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_id = get_identifier ("_Coro_resume_fn");
> +  coro_destroy_fn_id = get_identifier ("_Coro_destroy_fn");
> +  coro_promise_id = get_identifier ("_Coro_promise");
> +  coro_frame_needs_free_id = get_identifier ("_Coro_frame_needs_free");
> +  coro_frame_i_a_r_c_id = get_identifier ("_Coro_initial_await_resume_called");
> +  coro_resume_index_id = get_identifier ("_Coro_resume_index");
> +  coro_self_handle_id = get_identifier ("_Coro_self_handle");
> +  coro_actor_continue_id = get_identifier ("_Coro_actor_continue");
>   }
>   
>   /* Trees we only need to set up once.  */
> @@ -513,12 +535,12 @@ 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 ("self_h.proxy"),
> +	= build_lang_decl (VAR_DECL, coro_self_handle_id,
>   			   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 ("promise.proxy"),
> +	= build_lang_decl (VAR_DECL, coro_promise_id,
>   			   coro_info->promise_type);
>   
>         /* Note where we first saw a coroutine keyword.  */
> @@ -1864,10 +1886,6 @@ struct await_xform_data
>   {
>     tree actor_fn;   /* Decl for context.  */
>     tree actor_frame;
> -  tree promise_proxy;
> -  tree real_promise;
> -  tree self_h_proxy;
> -  tree real_self_h;
>   };
>   
>   /* When we built the await expressions, we didn't know the coro frame
> @@ -1888,7 +1906,6 @@ transform_await_expr (tree await_expr, await_xform_data *xform)
>     /* So, on entry, we have:
>        in : CO_AWAIT_EXPR (a, e_proxy, o, awr_call_vector, mode)
>   	  We no longer need a [it had diagnostic value, maybe?]
> -	  We need to replace the promise proxy in all elements
>   	  We need to replace the e_proxy in the awr_call.  */
>   
>     tree coro_frame_type = TREE_TYPE (xform->actor_frame);
> @@ -1914,16 +1931,6 @@ transform_await_expr (tree await_expr, await_xform_data *xform)
>         TREE_OPERAND (await_expr, 1) = as;
>       }
>   
> -  /* Now do the self_handle.  */
> -  data.from = xform->self_h_proxy;
> -  data.to = xform->real_self_h;
> -  cp_walk_tree (&await_expr, replace_proxy, &data, NULL);
> -
> -  /* Now do the promise.  */
> -  data.from = xform->promise_proxy;
> -  data.to = xform->real_promise;
> -  cp_walk_tree (&await_expr, replace_proxy, &data, NULL);
> -
>     return await_expr;
>   }
>   
> @@ -2110,15 +2117,13 @@ coro_get_frame_dtor (tree coro_fp, tree orig, tree frame_size,
>   
>   static void
>   build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
> -		tree orig, hash_map<tree, param_info> *param_uses,
> -		hash_map<tree, local_var_info> *local_var_uses,
> -		vec<tree, va_gc> *param_dtor_list, tree resume_fn_field,
> -		tree resume_idx_field, unsigned body_count, tree frame_size)
> +		tree orig, hash_map<tree, local_var_info> *local_var_uses,
> +		vec<tree, va_gc> *param_dtor_list,
> +		tree resume_idx_var, unsigned body_count, tree frame_size)
>   {
>     verify_stmt_tree (fnbody);
>     /* Some things we inherit from the original function.  */
>     tree handle_type = get_coroutine_handle_type (orig);
> -  tree self_h_proxy = get_coroutine_self_handle_proxy (orig);
>     tree promise_type = get_coroutine_promise_type (orig);
>     tree promise_proxy = get_coroutine_promise_proxy (orig);
>   
> @@ -2136,11 +2141,12 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>     tree top_block = make_node (BLOCK);
>     BIND_EXPR_BLOCK (actor_bind) = top_block;
>   
> -  tree continuation = coro_build_artificial_var (loc, "_Coro_actor_continue",
> +  tree continuation = coro_build_artificial_var (loc, coro_actor_continue_id,
>   						 void_coro_handle_type, actor,
>   						 NULL_TREE);
>   
>     BIND_EXPR_VARS (actor_bind) = continuation;
> +  BLOCK_VARS (top_block) = BIND_EXPR_VARS (actor_bind) ;
>   
>     /* Link in the block associated with the outer scope of the re-written
>        function body.  */
> @@ -2198,9 +2204,8 @@ 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 ("__resume_at");
> -  tree rat_field = lookup_member (coro_frame_type, resume_idx_name, 1, 0,
> -				  tf_warning_or_error);
> +  tree rat_field = lookup_member (coro_frame_type, coro_resume_index_id,
> +				  1, 0, tf_warning_or_error);
>     tree rat = build3 (COMPONENT_REF, short_unsigned_type_node, actor_frame,
>   		     rat_field, NULL_TREE);
>   
> @@ -2302,14 +2307,8 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>     tree r = build_stmt (loc, LABEL_EXPR, actor_begin_label);
>     add_stmt (r);
>   
> -  /* actor's version of the promise.  */
> -  tree ap_m = lookup_member (coro_frame_type, get_identifier ("__p"), 1, 0,
> -			     tf_warning_or_error);
> -  tree ap = build_class_member_access_expr (actor_frame, ap_m, NULL_TREE, false,
> -					    tf_warning_or_error);
> -
>     /* actor's coroutine 'self handle'.  */
> -  tree ash_m = lookup_member (coro_frame_type, get_identifier ("__self_h"), 1,
> +  tree ash_m = lookup_member (coro_frame_type, coro_self_handle_id, 1,
>   			      0, tf_warning_or_error);
>     tree ash = build_class_member_access_expr (actor_frame, ash_m, NULL_TREE,
>   					     false, tf_warning_or_error);
> @@ -2329,37 +2328,13 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>     /* Now we know the real promise, and enough about the frame layout to
>        decide where to put things.  */
>   
> -  await_xform_data xform
> -    = {actor, actor_frame, promise_proxy, ap, self_h_proxy, ash};
> +  await_xform_data xform = {actor, actor_frame};
>   
>     /* Transform the await expressions in the function body.  Only do each
>        await tree once!  */
>     hash_set<tree> pset;
>     cp_walk_tree (&fnbody, transform_await_wrapper, &xform, &pset);
>   
> -  /* Now replace the promise proxy with its real value.  */
> -  proxy_replace p_data;
> -  p_data.from = promise_proxy;
> -  p_data.to = ap;
> -  cp_walk_tree (&fnbody, replace_proxy, &p_data, NULL);
> -
> -  /* The rewrite of the function adds code to set the __resume field to
> -     nullptr when the coroutine is done and also the index to zero when
> -     calling an unhandled exception.  These are represented by two proxies
> -     in the function, so rewrite them to the proper frame access.  */
> -  tree resume_m
> -    = lookup_member (coro_frame_type, get_identifier ("__resume"),
> -		     /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
> -  tree res_x = build_class_member_access_expr (actor_frame, resume_m, NULL_TREE,
> -					       false, tf_warning_or_error);
> -  p_data.from = resume_fn_field;
> -  p_data.to = res_x;
> -  cp_walk_tree (&fnbody, replace_proxy, &p_data, NULL);
> -
> -  p_data.from = resume_idx_field;
> -  p_data.to = rat;
> -  cp_walk_tree (&fnbody, replace_proxy, &p_data, NULL);
> -
>     /* Add in our function body with the co_returns rewritten to final form.  */
>     add_stmt (fnbody);
>   
> @@ -2368,7 +2343,7 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>     add_stmt (r);
>   
>     /* Destructors for the things we built explicitly.  */
> -  r = build_special_member_call (ap, complete_dtor_identifier, NULL,
> +  r = build_special_member_call (promise_proxy, complete_dtor_identifier, NULL,
>   				 promise_type, LOOKUP_NORMAL,
>   				 tf_warning_or_error);
>     add_stmt (r);
> @@ -2381,7 +2356,7 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>     /* Here deallocate the frame (if we allocated it), which we will have at
>        present.  */
>     tree fnf_m
> -    = lookup_member (coro_frame_type, get_identifier ("__frame_needs_free"), 1,
> +    = lookup_member (coro_frame_type, coro_frame_needs_free_id, 1,
>   		     0, tf_warning_or_error);
>     tree fnf2_x = build_class_member_access_expr (actor_frame, fnf_m, NULL_TREE,
>   						false, tf_warning_or_error);
> @@ -2460,18 +2435,10 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>     gcc_checking_assert (maybe_cleanup_point_expr_void (r) == r);
>     add_stmt (r);
>   
> -  /* We will need to know which resume point number should be encoded.  */
> -  tree res_idx_m
> -    = lookup_member (coro_frame_type, resume_idx_name,
> -		     /*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,
> -				      tf_warning_or_error);
> -
>     /* We've now rewritten the tree and added the initial and final
>        co_awaits.  Now pass over the tree and expand the co_awaits.  */
>   
> -  coro_aw_data data = {actor, actor_fp, resume_pt_number, NULL_TREE,
> +  coro_aw_data data = {actor, actor_fp, resume_idx_var, NULL_TREE,
>   		       ash, del_promise_label, ret_label,
>   		       continue_label, continuation, 2};
>     cp_walk_tree (&actor_body, await_statement_expander, &data, NULL);
> @@ -2485,7 +2452,7 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
>   }
>   
>   /* The prototype 'destroy' function :
> -   frame->__resume_at |= 1;
> +   frame->__Coro_resume_index |= 1;
>      actor (frame);  */
>   
>   static void
> @@ -2504,11 +2471,10 @@ 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 ("__resume_at");
> -  tree rat_field = lookup_member (coro_frame_type, resume_idx_name, 1, 0,
> -				  tf_warning_or_error);
> -  tree rat = build3 (COMPONENT_REF, short_unsigned_type_node, destr_frame,
> -		     rat_field, NULL_TREE);
> +  tree rat_field = lookup_member (coro_frame_type, coro_resume_index_id,
> +				  1, 0, tf_warning_or_error);
> +  tree rat = build3 (COMPONENT_REF, short_unsigned_type_node,
> +			 destr_frame, rat_field, NULL_TREE);
>   
>     /* _resume_at |= 1 */
>     tree dstr_idx = build2 (BIT_IOR_EXPR, short_unsigned_type_node, rat,
> @@ -3927,6 +3893,7 @@ register_local_var_uses (tree *stmt, int *do_subtree, void *d)
>   	     identify them in the coroutine frame.  */
>   	  tree lvname = DECL_NAME (lvar);
>   	  char *buf;
> +
>   	  /* The outermost bind scope contains the artificial variables that
>   	     we inject to implement the coro state machine.  We want to be able
>   	     to inspect these in debugging.  */
> @@ -3936,7 +3903,7 @@ register_local_var_uses (tree *stmt, int *do_subtree, void *d)
>   	    buf = xasprintf ("%s_%u_%u", IDENTIFIER_POINTER (lvname),
>   			     lvd->nest_depth, lvd->bind_indx);
>   	  else
> -	    buf = xasprintf ("_D%u.%u.%u", DECL_UID (lvar), lvd->nest_depth,
> +	    buf = xasprintf ("_D%u_%u_%u", DECL_UID (lvar), lvd->nest_depth,
>   			     lvd->bind_indx);
>   	  /* TODO: Figure out if we should build a local type that has any
>   	     excess alignment or size from the original decl.  */
> @@ -4023,8 +3990,8 @@ coro_build_actor_or_destroy_function (tree orig, tree fn_type,
>   
>   static tree
>   coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
> -			    tree resume_fn_ptr_type, tree& resume_fn_field,
> -			    tree& resume_idx_field, tree& fs_label)
> +			    tree resume_fn_ptr_type,
> +			    tree& resume_idx_var, tree& fs_label)
>   {
>     /* This will be our new outer scope.  */
>     tree update_body = build3 (BIND_EXPR, void_type_node, NULL, NULL, NULL);
> @@ -4057,7 +4024,6 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
>   
>     /* Wrap the function body in a try {} catch (...) {} block, if exceptions
>        are enabled.  */
> -  tree promise = get_coroutine_promise_proxy (orig);
>     tree var_list = NULL_TREE;
>     tree initial_await = build_init_or_final_await (fn_start, false);
>   
> @@ -4068,24 +4034,61 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
>     tree return_void
>       = get_coroutine_return_void_expr (current_function_decl, fn_start, false);
>   
> +  /* The pointer to the resume function.  */
> +  tree resume_fn_ptr
> +    = coro_build_artificial_var (fn_start, coro_resume_fn_id,
> +				 resume_fn_ptr_type, orig, NULL_TREE);
> +  DECL_CHAIN (resume_fn_ptr) = var_list;
> +  var_list = resume_fn_ptr;
> +  add_decl_expr (resume_fn_ptr);
> +
>     /* We will need to be able to set the resume function pointer to nullptr
>        to signal that the coroutine is 'done'.  */
> -  resume_fn_field
> -    = build_lang_decl (VAR_DECL, get_identifier ("resume.fn.ptr.proxy"),
> -		       resume_fn_ptr_type);
> -  DECL_ARTIFICIAL (resume_fn_field) = true;
>     tree zero_resume
>       = build1 (CONVERT_EXPR, resume_fn_ptr_type, integer_zero_node);
> -  zero_resume
> -    = build2 (INIT_EXPR, resume_fn_ptr_type, resume_fn_field, zero_resume);
> -  /* Likewise, the resume index needs to be reset.  */
> -  resume_idx_field
> -    = build_lang_decl (VAR_DECL, get_identifier ("resume.index.proxy"),
> -		       short_unsigned_type_node);
> -  DECL_ARTIFICIAL (resume_idx_field) = true;
> -  tree zero_resume_idx = build_int_cst (short_unsigned_type_node, 0);
> -  zero_resume_idx = build2 (INIT_EXPR, short_unsigned_type_node,
> -			    resume_idx_field, zero_resume_idx);
> +
> +  /* The pointer to the destroy function.  */
> +  tree var = coro_build_artificial_var (fn_start, coro_destroy_fn_id,
> +					resume_fn_ptr_type, orig, NULL_TREE);
> +  DECL_CHAIN (var) = var_list;
> +  var_list = var;
> +  add_decl_expr (var);
> +
> +  /* The promise was created on demand when parsing we now link it into
> +      our scope.  */
> +  tree promise = get_coroutine_promise_proxy (orig);
> +  DECL_CONTEXT (promise) = orig;
> +  DECL_SOURCE_LOCATION (promise) = fn_start;
> +  DECL_CHAIN (promise) = var_list;
> +  var_list = promise;
> +  add_decl_expr (promise);
> +
> +  /* We need a handle to this coroutine, which is passed to every
> +     await_suspend().  This was created on demand when parsing we now link it
> +     into our scope.  */
> +  var = get_coroutine_self_handle_proxy (orig);
> +  DECL_CONTEXT (var) = orig;
> +  DECL_SOURCE_LOCATION (var) = fn_start;
> +  DECL_CHAIN (var) = var_list;
> +  var_list = var;
> +  add_decl_expr (var);
> +
> +
> +  /* We create a resume index, this is initialized in the ramp.  */
> +  resume_idx_var
> +    = coro_build_artificial_var (fn_start, coro_resume_index_id,
> +				 short_unsigned_type_node, orig, NULL_TREE);
> +  DECL_CHAIN (resume_idx_var) = var_list;
> +  var_list = resume_idx_var;
> +  add_decl_expr (resume_idx_var);
> +
> +  /* If the coroutine has a frame that needs to be freed, this will be set by
> +     the ramp.  */
> +  var = coro_build_artificial_var (fn_start, coro_frame_needs_free_id,
> +				   boolean_type_node, orig, NULL_TREE);
> +  DECL_CHAIN (var) = var_list;
> +  var_list = var;
> +  add_decl_expr (var);
>   
>     if (flag_exceptions)
>       {
> @@ -4097,8 +4100,7 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
>         /* Create and initialize the initial-await-resume-called variable per
>   	 [dcl.fct.def.coroutine] / 5.3.  */
>         tree i_a_r_c
> -	= coro_build_artificial_var (fn_start,
> -				     "_Coro_initial_await_resume_called",
> +	= coro_build_artificial_var (fn_start, coro_frame_i_a_r_c_id,
>   				     boolean_type_node, orig,
>   				     boolean_false_node);
>         DECL_CHAIN (i_a_r_c) = var_list;
> @@ -4151,10 +4153,14 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
>   	 If the unhandled exception method returns, then we continue
>   	 to the final await expression (which duplicates the clearing of
>   	 the field). */
> -      finish_expr_stmt (zero_resume);
> -      finish_expr_stmt (zero_resume_idx);
> -      ueh = maybe_cleanup_point_expr_void (ueh);
> -      add_stmt (ueh);
> +      tree r = build2 (MODIFY_EXPR, resume_fn_ptr_type, resume_fn_ptr,
> +		       zero_resume);
> +      finish_expr_stmt (r);
> +      tree short_zero = build_int_cst (short_unsigned_type_node, 0);
> +      r = build2 (MODIFY_EXPR, short_unsigned_type_node, resume_idx_var,
> +		  short_zero);
> +      finish_expr_stmt (r);
> +      finish_expr_stmt (ueh);
>         finish_handler (handler);
>         TRY_HANDLERS (tcb) = pop_stmt_list (TRY_HANDLERS (tcb));
>       }
> @@ -4189,6 +4195,8 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
>     /* Before entering the final suspend point, we signal that this point has
>        been reached by setting the resume function pointer to zero (this is
>        what the 'done()' builtin tests) as per the current ABI.  */
> +  zero_resume = build2 (MODIFY_EXPR, resume_fn_ptr_type, resume_fn_ptr,
> +			zero_resume);
>     finish_expr_stmt (zero_resume);
>     finish_expr_stmt (build_init_or_final_await (fn_start, true));
>     BIND_EXPR_BODY (update_body) = pop_stmt_list (BIND_EXPR_BODY (update_body));
> @@ -4216,15 +4224,15 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
>    declare a dummy coro frame.
>    struct _R_frame {
>     using handle_type = coro::coroutine_handle<coro1::promise_type>;
> -  void (*__resume)(_R_frame *);
> -  void (*__destroy)(_R_frame *);
> -  coro1::promise_type __p;
> -  bool frame_needs_free; free the coro frame mem if set.
> -  bool i_a_r_c; [dcl.fct.def.coroutine] / 5.3
> -  short __resume_at;
> -  handle_type self_handle;
> -  (maybe) parameter copies.
> -  (maybe) local variables saved (including awaitables)
> +  void (*_Coro_resume_fn)(_R_frame *);
> +  void (*_Coro_destroy_fn)(_R_frame *);
> +  coro1::promise_type _Coro_promise;
> +  bool _Coro_frame_needs_free; free the coro frame mem if set.
> +  bool _Coro_i_a_r_c; [dcl.fct.def.coroutine] / 5.3
> +  short _Coro_resume_index;
> +  handle_type _Coro_self_handle;
> +  parameter copies (were required).
> +  local variables saved (including awaitables)
>     (maybe) trailing space.
>    };  */
>   
> @@ -4316,7 +4324,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>   
>     /* 2. Types we need to define or look up.  */
>   
> -  tree fr_name = get_fn_local_identifier (orig, "frame");
> +  tree fr_name = get_fn_local_identifier (orig, "Frame");
>     tree coro_frame_type = xref_tag (record_type, fr_name);
>     DECL_CONTEXT (TYPE_NAME (coro_frame_type)) = current_scope ();
>     tree coro_frame_ptr = build_pointer_type (coro_frame_type);
> @@ -4333,33 +4341,16 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>     /* Construct the wrapped function body; we will analyze this to determine
>        the requirements for the coroutine frame.  */
>   
> -  tree resume_fn_field = NULL_TREE;
> -  tree resume_idx_field = NULL_TREE;
> +  tree resume_idx_var = NULL_TREE;
>     tree fs_label = NULL_TREE;
>     fnbody = coro_rewrite_function_body (fn_start, fnbody, orig,
> -				       act_des_fn_ptr, resume_fn_field,
> -				       resume_idx_field, fs_label);
> +				       act_des_fn_ptr,
> +				       resume_idx_var, fs_label);
>     /* Build our dummy coro frame layout.  */
>     coro_frame_type = begin_class_definition (coro_frame_type);
>   
> +  /* The fields for the coro frame.  */
>     tree field_list = NULL_TREE;
> -  tree resume_name
> -    = coro_make_frame_entry (&field_list, "__resume",
> -			     act_des_fn_ptr, fn_start);
> -  tree destroy_name
> -    = coro_make_frame_entry (&field_list, "__destroy",
> -			     act_des_fn_ptr, fn_start);
> -  tree promise_name
> -    = coro_make_frame_entry (&field_list, "__p", promise_type, fn_start);
> -  tree fnf_name = coro_make_frame_entry (&field_list, "__frame_needs_free",
> -					 boolean_type_node, fn_start);
> -  tree resume_idx_name
> -    = coro_make_frame_entry (&field_list, "__resume_at",
> -			     short_unsigned_type_node, fn_start);
> -
> -  /* We need a handle to this coroutine, which is passed to every
> -     await_suspend().  There's no point in creating it over and over.  */
> -  (void) coro_make_frame_entry (&field_list, "__self_h", handle_type, fn_start);
>   
>     /* Now add in fields for function params (if there are any).
>        We do not attempt elision of copies at this stage, we do analyze the
> @@ -4417,14 +4408,14 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>   	  if (DECL_NAME (arg))
>   	    {
>   	      tree pname = DECL_NAME (arg);
> -	      buf = xasprintf ("__parm.%s", IDENTIFIER_POINTER (pname));
> +	      buf = xasprintf ("_P_%s", IDENTIFIER_POINTER (pname));
>   	    }
>   	  else
> -	    buf = xasprintf ("__unnamed_parm.%d", no_name_parm++);
> +	    buf = xasprintf ("_P_unnamed_%d", no_name_parm++);
>   
>   	  if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (parm.frame_type))
>   	    {
> -	      char *gbuf = xasprintf ("%s.live", buf);
> +	      char *gbuf = xasprintf ("%s_live", buf);
>   	      parm.guard_var
>   		= build_lang_decl (VAR_DECL, get_identifier (gbuf),
>   				   boolean_type_node);
> @@ -4761,8 +4752,8 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>   
>     /* For now, once allocation has succeeded we always assume that this needs
>        destruction, there's no impl. for frame allocation elision.  */
> -  tree fnf_m
> -    = lookup_member (coro_frame_type, fnf_name, 1, 0, tf_warning_or_error);
> +  tree fnf_m = lookup_member (coro_frame_type, coro_frame_needs_free_id,
> +			      1, 0,tf_warning_or_error);
>     tree fnf_x = build_class_member_access_expr (deref_fp, fnf_m, NULL_TREE,
>   					       false, tf_warning_or_error);
>     r = build2 (INIT_EXPR, boolean_type_node, fnf_x, boolean_true_node);
> @@ -4773,24 +4764,22 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>   
>     tree actor_addr = build1 (ADDR_EXPR, act_des_fn_ptr, actor);
>     tree resume_m
> -    = lookup_member (coro_frame_type, resume_name,
> +    = lookup_member (coro_frame_type, coro_resume_fn_id,
>   		     /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
>     tree resume_x = build_class_member_access_expr (deref_fp, resume_m, NULL_TREE,
>   						  false, tf_warning_or_error);
>     r = build2_loc (fn_start, INIT_EXPR, act_des_fn_ptr, resume_x, actor_addr);
> -  r = coro_build_cvt_void_expr_stmt (r, fn_start);
> -  add_stmt (r);
> +  finish_expr_stmt (r);
>   
>     tree destroy_addr = build1 (ADDR_EXPR, act_des_fn_ptr, destroy);
>     tree destroy_m
> -    = lookup_member (coro_frame_type, destroy_name,
> +    = lookup_member (coro_frame_type, coro_destroy_fn_id,
>   		     /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
>     tree destroy_x
>       = build_class_member_access_expr (deref_fp, destroy_m, NULL_TREE, false,
>   				      tf_warning_or_error);
>     r = build2_loc (fn_start, INIT_EXPR, act_des_fn_ptr, destroy_x, destroy_addr);
> -  r = coro_build_cvt_void_expr_stmt (r, fn_start);
> -  add_stmt (r);
> +  finish_expr_stmt (r);
>   
>     /* [dcl.fct.def.coroutine] /13
>        When a coroutine is invoked, a copy is created for each coroutine
> @@ -4881,7 +4870,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>   
>     /* Set up the promise.  */
>     tree promise_m
> -    = lookup_member (coro_frame_type, promise_name,
> +    = lookup_member (coro_frame_type, coro_promise_id,
>   		     /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
>   
>     tree p = build_class_member_access_expr (deref_fp, promise_m, NULL_TREE,
> @@ -5027,9 +5016,9 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>   			      boolean_type_node);
>         finish_expr_stmt (r);
>       }
> -  /* Initialize the resume_idx_name to 0, meaning "not started".  */
> +  /* Initialize the resume_idx_var to 0, meaning "not started".  */
>     tree resume_idx_m
> -    = lookup_member (coro_frame_type, resume_idx_name,
> +    = lookup_member (coro_frame_type, coro_resume_index_id,
>   		     /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
>     tree resume_idx
>       = build_class_member_access_expr (deref_fp, resume_idx_m, NULL_TREE, false,
> @@ -5172,9 +5161,9 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
>     push_deferring_access_checks (dk_no_check);
>   
>     /* Build the actor...  */
> -  build_actor_fn (fn_start, coro_frame_type, actor, fnbody, orig, param_uses,
> -		  &local_var_uses, param_dtor_list, resume_fn_field,
> -		  resume_idx_field, body_aw_points.await_number, frame_size);
> +  build_actor_fn (fn_start, coro_frame_type, actor, fnbody, orig,
> +		  &local_var_uses, param_dtor_list,
> +		  resume_idx_var, body_aw_points.await_number, frame_size);
>   
>     /* Destroyer ... */
>     build_destroy_fn (fn_start, coro_frame_type, destroy, actor);
>