| Message ID | 566C32D6.90903@acm.org |
|---|---|
| State | New |
| Headers | show |
On 12/12/15 09:44, Nathan Sidwell wrote: > On 12/11/15 13:15, Jan Hubicka wrote: >>> Jan, > >>> b) augment can_replace_by_local_alias_in_vtable to check whether >>> aliases can be created? >> >> I think this is best: can_replace_by_local_alias_in_vtable exists to prevent the >> body walk in cases we are not going to create the alias. This is because in LTO >> we may need to stream in the constructor from the object file that is not >> copletely >> free and thus it is better to not touch it unless necessary. > > I went with augmenting can_replace_by_local_alias, which > can_replace_by_local_alias_in_vtable calls. I also noticed that both should be > static, which I suspect will encourage the inliner to go inline them and then > determine a bunch of code is unreachable. > > tested on x86-linux and ptx-none. > > ok? https://gcc.gnu.org/ml/gcc-patches/2015-12/msg01324.html ping? nathan
> On 12/12/15 09:44, Nathan Sidwell wrote: > >On 12/11/15 13:15, Jan Hubicka wrote: > >>>Jan, > > > >>>b) augment can_replace_by_local_alias_in_vtable to check whether > >>>aliases can be created? > >> > >>I think this is best: can_replace_by_local_alias_in_vtable exists to prevent the > >>body walk in cases we are not going to create the alias. This is because in LTO > >>we may need to stream in the constructor from the object file that is not > >>copletely > >>free and thus it is better to not touch it unless necessary. > > > >I went with augmenting can_replace_by_local_alias, which > >can_replace_by_local_alias_in_vtable calls. I also noticed that both should be > >static, which I suspect will encourage the inliner to go inline them and then > >determine a bunch of code is unreachable. > > > >tested on x86-linux and ptx-none. > > > >ok? > > https://gcc.gnu.org/ml/gcc-patches/2015-12/msg01324.html OK, thanks! Honza > > ping? > > nathan
2015-12-12 Nathan Sidwell <nathan@acm.org> * ipa-visibility.c (can_replace_by_local_alias): Make static, check ASM_OUTPUT_DEF. (can_replace_by_local_alias_in_vtable): Make static. (function_and_variable_visibility): Reformat overlong comment. Index: ipa-visibility.c =================================================================== --- ipa-visibility.c (revision 231571) +++ ipa-visibility.c (working copy) @@ -329,9 +329,13 @@ varpool_node::externally_visible_p (void Local aliases save dynamic linking overhead and enable more optimizations. */ -bool +static bool can_replace_by_local_alias (symtab_node *node) { +#ifndef ASM_OUTPUT_DEF + /* If aliases aren't supported, we can't do replacement. */ + return false; +#endif /* Weakrefs have a reason to be non-local. Be sure we do not replace them. */ while (node->transparent_alias && node->definition && !node->weakref) @@ -344,11 +348,11 @@ can_replace_by_local_alias (symtab_node && !node->can_be_discarded_p ()); } -/* Return true if we can replace refernece to NODE by local alias +/* Return true if we can replace reference to NODE by local alias within a virtual table. Generally we can replace function pointers and virtual table pointers. */ -bool +static bool can_replace_by_local_alias_in_vtable (symtab_node *node) { if (is_a <varpool_node *> (node) @@ -592,10 +596,11 @@ function_and_variable_visibility (bool w if (!node->local.local) node->local.local |= node->local_p (); - /* If we know that function can not be overwritten by a different semantics - and moreover its section can not be discarded, replace all direct calls - by calls to an noninterposable alias. This make dynamic linking - cheaper and enable more optimization. + /* If we know that function can not be overwritten by a + different semantics and moreover its section can not be + discarded, replace all direct calls by calls to an + noninterposable alias. This make dynamic linking cheaper and + enable more optimization. TODO: We can also update virtual tables. */ if (node->callers