c++, coroutines: Simplify separation of the user function body and ramp.
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Commit Message
This fixes a (so far unreported) bug where we would handle noexcept ramps
correctly, but omit exception specs - take this opportunity to simplify.
Tested on x86_64-darwin, OK for trunk?
thanks
Iain
--- 8< ---
We need to separate the original user-authored function body from the
definition of the ramp function (which is what is called instead).
The function body tree is either in DECL_SAVED_TREE or the first operand
of current_eh_spec_block (for functions with an EH spec).
This version simplifies the process by extrating the second case directly
instead of inspecting the DECL_SAVED_TREE trees to discover it.
gcc/cp/ChangeLog:
* coroutines.cc (use_eh_spec_block): New.
(split_coroutine_body_from_ramp): New.
(morph_fn_to_coro): Use split_coroutine_body_from_ramp().
Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
---
gcc/cp/coroutines.cc | 97 ++++++++++++++++++++++++--------------------
1 file changed, 52 insertions(+), 45 deletions(-)
Comments
On 8/2/24 6:50 AM, Iain Sandoe wrote:
> This fixes a (so far unreported) bug where we would handle noexcept ramps
> correctly, but omit exception specs - take this opportunity to simplify.
> Tested on x86_64-darwin, OK for trunk?
> thanks
> Iain
>
> --- 8< ---
>
> We need to separate the original user-authored function body from the
> definition of the ramp function (which is what is called instead).
> The function body tree is either in DECL_SAVED_TREE or the first operand
> of current_eh_spec_block (for functions with an EH spec).
> This version simplifies the process by extrating the second case directly
typo
> instead of inspecting the DECL_SAVED_TREE trees to discover it.
>
> gcc/cp/ChangeLog:
>
> * coroutines.cc (use_eh_spec_block): New.
> (split_coroutine_body_from_ramp): New.
> (morph_fn_to_coro): Use split_coroutine_body_from_ramp().
>
> Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
> ---
> gcc/cp/coroutines.cc | 97 ++++++++++++++++++++++++--------------------
> 1 file changed, 52 insertions(+), 45 deletions(-)
>
> diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
> index af03f5e0f74..fc80a4ec24c 100644
> --- a/gcc/cp/coroutines.cc
> +++ b/gcc/cp/coroutines.cc
> @@ -4437,6 +4437,50 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
> return update_body;
> }
>
> +static bool
> +use_eh_spec_block (tree fn)
> +{
> + return (flag_exceptions && flag_enforce_eh_specs
> + && !type_throw_all_p (TREE_TYPE (fn)));
> +}
Rather than (partially) duplicate this function, let's make the one in
decl.cc non-static.
> +/* Extract the body of the function we are going to outline, leaving
> + to original function decl ready to build the ramp. */
> +
> +static tree
> +split_coroutine_body_from_ramp (tree fndecl, tree eh_spec_block)
Rather than pass current_eh_spec_block into this function through a
parameter, why not refer to it directly?
Jason
@@ -4437,6 +4437,50 @@ coro_rewrite_function_body (location_t fn_start, tree fnbody, tree orig,
return update_body;
}
+static bool
+use_eh_spec_block (tree fn)
+{
+ return (flag_exceptions && flag_enforce_eh_specs
+ && !type_throw_all_p (TREE_TYPE (fn)));
+}
+
+/* Extract the body of the function we are going to outline, leaving
+ to original function decl ready to build the ramp. */
+
+static tree
+split_coroutine_body_from_ramp (tree fndecl, tree eh_spec_block)
+{
+ tree body;
+ /* Once we've tied off the original user-authored body in fn_body.
+ Start the replacement synthesized ramp body. */
+
+ if (use_eh_spec_block (fndecl))
+ {
+ body = pop_stmt_list (TREE_OPERAND (eh_spec_block, 0));
+ TREE_OPERAND (eh_spec_block, 0) = push_stmt_list ();
+ }
+ else
+ {
+ body = pop_stmt_list (DECL_SAVED_TREE (fndecl));
+ DECL_SAVED_TREE (fndecl) = push_stmt_list ();
+ }
+
+ /* We can't validly get here with an empty statement list, since there's no
+ way for the FE to decide it's a coroutine in the absence of any code. */
+ gcc_checking_assert (body != NULL_TREE);
+
+ /* If we have an empty or erroneous function body, do not try to transform it
+ since that would potentially wrap errors. */
+ tree body_start = expr_first (body);
+ if (body_start == NULL_TREE || body_start == error_mark_node)
+ {
+ /* Restore the original state. */
+ add_stmt (body);
+ return NULL_TREE;
+ }
+ return body;
+}
+
/* Here we:
a) Check that the function and promise type are valid for a
coroutine.
@@ -4483,57 +4527,22 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
/* Discard the body, we can't process it further. */
pop_stmt_list (DECL_SAVED_TREE (orig));
DECL_SAVED_TREE (orig) = push_stmt_list ();
+ /* Match the expected nesting when an eh block is in use. */
+ if (use_eh_spec_block (orig))
+ current_eh_spec_block = begin_eh_spec_block ();
return false;
}
- /* We can't validly get here with an empty statement list, since there's no
- way for the FE to decide it's a coroutine in the absence of any code. */
- tree fnbody = pop_stmt_list (DECL_SAVED_TREE (orig));
- gcc_checking_assert (fnbody != NULL_TREE);
-
/* We don't have the locus of the opening brace - it's filled in later (and
there doesn't really seem to be any easy way to get at it).
The closing brace is assumed to be input_location. */
location_t fn_start = DECL_SOURCE_LOCATION (orig);
- gcc_rich_location fn_start_loc (fn_start);
-
- /* Initial processing of the function-body.
- If we have no expressions or just an error then punt. */
- tree body_start = expr_first (fnbody);
- if (body_start == NULL_TREE || body_start == error_mark_node)
- {
- DECL_SAVED_TREE (orig) = push_stmt_list ();
- append_to_statement_list (fnbody, &DECL_SAVED_TREE (orig));
- /* Suppress warnings about the missing return value. */
- suppress_warning (orig, OPT_Wreturn_type);
- return false;
- }
-
- /* So, we've tied off the original user-authored body in fn_body.
-
- Start the replacement synthesized ramp body as newbody.
- If we encounter a fatal error we might return a now-empty body.
- Note, the returned ramp body is not 'popped', to be compatible with
- the way that decl.cc handles regular functions, the scope pop is done
- in the caller. */
-
- tree newbody = push_stmt_list ();
- DECL_SAVED_TREE (orig) = newbody;
-
- /* If our original body is noexcept, then that's what we apply to our
- generated ramp, transfer any MUST_NOT_THOW_EXPR to that. */
- bool is_noexcept = TREE_CODE (body_start) == MUST_NOT_THROW_EXPR;
- if (is_noexcept)
- {
- /* The function body we will continue with is the single operand to
- the must-not-throw. */
- fnbody = TREE_OPERAND (body_start, 0);
- /* Transfer the must-not-throw to the ramp body. */
- add_stmt (body_start);
- /* Re-start the ramp as must-not-throw. */
- TREE_OPERAND (body_start, 0) = push_stmt_list ();
- }
+ /* FIXME: This has the hidden side-effect of preparing the current function
+ to be the ramp. */
+ tree fnbody = split_coroutine_body_from_ramp (orig, current_eh_spec_block);
+ if (!fnbody)
+ return false;
/* If the original function has a return value with a non-trivial DTOR
and the body contains a var with a DTOR that might throw, the decl is
@@ -5059,7 +5068,6 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
if (get_ro == error_mark_node)
{
BIND_EXPR_BODY (ramp_bind) = pop_stmt_list (ramp_body);
- DECL_SAVED_TREE (orig) = newbody;
/* Suppress warnings about the missing return value. */
suppress_warning (orig, OPT_Wreturn_type);
return false;
@@ -5286,7 +5294,6 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
pop_deferring_access_checks ();
- DECL_SAVED_TREE (orig) = newbody;
/* Link our new functions into the list. */
TREE_CHAIN (destroy) = TREE_CHAIN (orig);
TREE_CHAIN (actor) = destroy;