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Re: [PATCH: PR /3187] C++ space optimization: declone delete destructor
Thank you Richard, unconditionally construct deleting destructor this way is
also a good idea, since it can still get inlined later. I've modified the
patch according to your suggestion. Could you take another look?
I've run the boot-strap and gcc regression tests again, and without any new
failure.
thanks
Wei Guozhi
Index: optimize.c
===================================================================
--- optimize.c (revision 151143)
+++ optimize.c (working copy)
@@ -106,6 +106,41 @@ clone_body (tree clone, tree fn, void *a
append_to_statement_list_force (stmts, &DECL_SAVED_TREE (clone));
}
+/* DELETE_DTOR is a delete destructor whose body will be build.
+ COMPLETE_DTOR is the corresponding complete destructor. */
+
+static void
+build_delete_destructor_body (tree delete_dtor, tree complete_dtor)
+{
+ tree call_dtor, call_delete;
+ tree parm = DECL_ARGUMENTS (delete_dtor);
+ tree virtual_size = cxx_sizeof (current_class_type);
+
+ /* Call the corresponding complete destructor. */
+ gcc_assert (complete_dtor);
+ call_dtor = build_cxx_call (complete_dtor, 1, &parm);
+ add_stmt (call_dtor);
+
+ add_stmt (build_stmt (0, LABEL_EXPR, cdtor_label));
+
+ /* Call the delete function. */
+ call_delete = build_op_delete_call(DELETE_EXPR, current_class_ptr,
+ virtual_size,
+ /*global_p=*/false,
+ /*placement=*/NULL_TREE,
+ /*alloc_fn=*/NULL_TREE);
+ add_stmt (call_delete);
+
+ /* Return the address of the object. */
+ if (targetm.cxx.cdtor_returns_this ())
+ {
+ tree val = DECL_ARGUMENTS (delete_dtor);
+ val = build2 (MODIFY_EXPR, TREE_TYPE (val),
+ DECL_RESULT (delete_dtor), val);
+ add_stmt (build_stmt (0, RETURN_EXPR, val));
+ }
+}
+
/* FN is a function that has a complete body. Clone the body as
necessary. Returns nonzero if there's no longer any need to
process the main body. */
@@ -114,6 +149,7 @@ bool
maybe_clone_body (tree fn)
{
tree clone;
+ tree complete_dtor = NULL_TREE;
bool first = true;
/* We only clone constructors and destructors. */
@@ -124,6 +160,15 @@ maybe_clone_body (tree fn)
/* Emit the DWARF1 abstract instance. */
(*debug_hooks->deferred_inline_function) (fn);
+ /* Look for the complete destructor which may be used to build the
+ delete destructor. */
+ FOR_EACH_CLONE (clone, fn)
+ if (DECL_NAME (clone) == complete_dtor_identifier)
+ {
+ complete_dtor = clone;
+ break;
+ }
+
/* We know that any clones immediately follow FN in the TYPE_METHODS
list. */
push_to_top_level ();
@@ -224,8 +269,14 @@ maybe_clone_body (tree fn)
clone_parm = DECL_RESULT (clone);
*pointer_map_insert (decl_map, parm) = clone_parm;
}
- /* Clone the body. */
- clone_body (clone, fn, decl_map);
+
+ /* Build the delete destructor by calling complete destructor
+ and delete function. */
+ if (DECL_NAME (clone) == deleting_dtor_identifier)
+ build_delete_destructor_body (clone, complete_dtor);
+ else
+ /* Clone the body. */
+ clone_body (clone, fn, decl_map);
/* Clean up. */
pointer_map_destroy (decl_map);
On Thu, Sep 3, 2009 at 10:20 PM, Richard
Guenther<richard.guenther@gmail.com> wrote:
> On Thu, Sep 3, 2009 at 4:04 PM, Carrot Wei<carrot@google.com> wrote:
>> This patch fixes a small part of
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3187
>>
>> The delete destructor(D0) always contains the content of complete
>> desturctor(D1) followed by a function call to delete. So instead of cloning
>> the abstract destructor function body to the delete destructor(D0), we
>> can generate a function call to complete destructor(D1) followed by a function
>> call to delete.
>>
>> This method doesn't break the ABI or linker compatibility.
>>
>> With this patch we can reduce 2.59% instructions for an open source 2d library
>> skia on arm. Some function call to complete destructor(D1) will be inlined in
>> later pass. So more instructions can be removed if we can do better inlining.
>>
>> Test:
>> Bootstrapped on linux-x86.
>> gcc regression tests without new failure.
>>
>>
>> ChangeLog:
>> 2009-09-03 ?Wei Guozhi ?<carrot@google.com>
>>
>> ? ? ? ?PR /3187
>> ? ? ? ?* cp/optimize.c (build_delete_destructor_body): New function.
>> ? ? ? ?(maybe_clone_body): Call build_delete_destructor_body if optimize for
>> ? ? ? ?size.
>>
>> thanks
>> Guozhi
>>
>>
>>
>> Index: optimize.c
>> ===================================================================
>> --- optimize.c ?(revision 151143)
>> +++ optimize.c ?(working copy)
>> @@ -106,6 +106,41 @@ clone_body (tree clone, tree fn, void *a
>> ? append_to_statement_list_force (stmts, &DECL_SAVED_TREE (clone));
>> ?}
>>
>> +/* DELETE_DTOR is a delete destructor whose body will be build.
>> + ? COMPLETE_DTOR is the corresponding complete destructor. ?*/
>> +
>> +static void
>> +build_delete_destructor_body (tree delete_dtor, tree complete_dtor)
>> +{
>> + ?tree call_dtor, call_delete;
>> + ?tree parm = DECL_ARGUMENTS (delete_dtor);
>> + ?tree virtual_size = cxx_sizeof (current_class_type);
>> +
>> + ?/* Call the corresponding complete destructor. ?*/
>> + ?gcc_assert (complete_dtor);
>> + ?call_dtor = build_cxx_call (complete_dtor, 1, &parm);
>> + ?add_stmt (call_dtor);
>> +
>> + ?add_stmt (build_stmt (0, LABEL_EXPR, cdtor_label));
>> +
>> + ?/* Call the delete function. ?*/
>> + ?call_delete = build_op_delete_call(DELETE_EXPR, current_class_ptr,
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? virtual_size,
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? /*global_p=*/false,
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? /*placement=*/NULL_TREE,
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? /*alloc_fn=*/NULL_TREE);
>> + ?add_stmt (call_delete);
>> +
>> + ?/* Return the address of the object. ?*/
>> + ?if (targetm.cxx.cdtor_returns_this ())
>> + ? ?{
>> + ? ? ?tree val = DECL_ARGUMENTS (delete_dtor);
>> + ? ? ?val = build2 (MODIFY_EXPR, TREE_TYPE (val),
>> + ? ? ? ? ? ? ? ? ? ?DECL_RESULT (delete_dtor), val);
>> + ? ? ?add_stmt (build_stmt (0, RETURN_EXPR, val));
>> + ? ?}
>> +}
>> +
>> ?/* FN is a function that has a complete body. ?Clone the body as
>> ? ?necessary. ?Returns nonzero if there's no longer any need to
>> ? ?process the main body. ?*/
>> @@ -114,6 +149,7 @@ bool
>> ?maybe_clone_body (tree fn)
>> ?{
>> ? tree clone;
>> + ?tree complete_dtor = NULL_TREE;
>> ? bool first = true;
>>
>> ? /* We only clone constructors and destructors. ?*/
>> @@ -124,6 +160,15 @@ maybe_clone_body (tree fn)
>> ? /* Emit the DWARF1 abstract instance. ?*/
>> ? (*debug_hooks->deferred_inline_function) (fn);
>>
>> + ?/* Look for the complete destructor which may be used to build the
>> + ? ? delete destructor. ?*/
>> + ?FOR_EACH_CLONE (clone, fn)
>> + ? ?if (DECL_NAME (clone) == complete_dtor_identifier)
>> + ? ? ?{
>> + ? ? ? ?complete_dtor = clone;
>> + ? ? ? ?break;
>> + ? ? ?}
>> +
>> ? /* We know that any clones immediately follow FN in the TYPE_METHODS
>> ? ? ?list. ?*/
>> ? push_to_top_level ();
>> @@ -224,8 +269,15 @@ maybe_clone_body (tree fn)
>> ? ? ? ? ?clone_parm = DECL_RESULT (clone);
>> ? ? ? ? ?*pointer_map_insert (decl_map, parm) = clone_parm;
>> ? ? ? ?}
>> - ? ? ?/* Clone the body. ?*/
>> - ? ? ?clone_body (clone, fn, decl_map);
>> +
>> + ? ? ?/* If we are optimizing for size, we can build the delete destructor
>> + ? ? ? ? by calling complete destructor and delete function. ?*/
>> + ? ? ?if ((DECL_NAME (clone) == deleting_dtor_identifier)
>> + ? ? ? ? ?&& optimize_function_for_size_p (DECL_STRUCT_FUNCTION (clone)))
>> + ? ? ? ?build_delete_destructor_body (clone, complete_dtor);
>
> Using optimize_function_for_size_p doens't make sense in the frontends.
> Just use optimize_size here. ?In fact I would suggest to unconditionally
> go with the build_delete_destructor_body variant.
>
> In future we might want to have a way to mark this call as always binding
> locally to avoid a relocation here and allow better optimization.
>
> Richard.
>
>> + ? ? ?else
>> + ? ? ? ?/* Clone the body. ?*/
>> + ? ? ? ?clone_body (clone, fn, decl_map);
>>
>> ? ? ? /* Clean up. ?*/
>> ? ? ? pointer_map_destroy (decl_map);
>>
>