ipa-visibility TLC 2/n

Hi,
this patch adds code to rerite references in vtable initializers to local aliases
when doing so is a win.

Bootstrapped/regtested x86_64-linux, comitted.

Honza

	* ipa-visibility.c (can_replace_by_local_alias_in_vtable): New function.
	(update_vtable_references): New function.
	(function_and_variable_visibility): Rewrite also vtable initializers.
	* varpool.c (cgraph_variable_initializer_availability): Remove assert.

On Sun, May 25, 2014 at 6:54 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
> Hi,
> this patch adds code to rerite references in vtable initializers to local aliases
> when doing so is a win.
>
> Bootstrapped/regtested x86_64-linux, comitted.

This is the most likely patch to have caused build failures on
arm-linux-gnueabihf

My last successful build was 210908 as is evident from

http://gcc.gnu.org/ml/gcc-testresults/2014-05/msg02245.html

and between that and 210913 builds failed with the following error message.

I haven't dug further yet.


libtool: compile:
/work/trunk-nightlies/builds/build-210913/./gcc/xgcc -shared-libgcc
-B/work/trunk-nightlies/builds/build-210913/./gcc -nostdinc++
-L/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/src
-L/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/src/.libs
-L/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/libsupc++/.libs
-B/work/trunk-nightlies/installs/install-210913/armv7l-unknown-linux-gnueabihf/bin/
-B/work/trunk-nightlies/installs/install-210913/armv7l-unknown-linux-gnueabihf/lib/
-isystem /work/trunk-nightlies/installs/install-210913/armv7l-unknown-linux-gnueabihf/include
-isystem /work/trunk-nightlies/installs/install-210913/armv7l-unknown-linux-gnueabihf/sys-include
-I/work/gcc/libstdc++-v3/../libgcc
-I/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/armv7l-unknown-linux-gnueabihf
-I/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include
-I/work/gcc/libstdc++-v3/libsupc++ -D_GLIBCXX_SHARED
-fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual
-Wabi -fdiagnostics-show-location=once -ffunction-sections
-fdata-sections -frandom-seed=strstream.lo -g -O2 -D_GNU_SOURCE
-I/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward
-Wno-deprecated -c /work/gcc/libstdc++-v3/src/c++98/strstream.cc
-fPIC -DPIC -D_GLIBCXX_SHARED -o strstream.o
In file included from /work/gcc/libstdc++-v3/src/c++98/strstream.cc:44:0:
/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward/strstream:126:9:
error: std::istrstream::_ZTVSt10istrstream.localalias.0 causes a
section type conflict with std::istrstream::_ZTVSt10istrstream
   class istrstream : public basic_istream<char>
         ^
/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward/strstream:126:9:
note: _std::istrstream::_ZTVSt10istrstream_ was declared here
/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward/strstream:143:9:
error: std::ostrstream::_ZTVSt10ostrstream.localalias.1 causes a
section type conflict with std::ostrstream::_ZTVSt10ostrstream
   class ostrstream : public basic_ostream<char>
         ^
/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward/strstream:143:9:
note: _std::ostrstream::_ZTVSt10ostrstream_ was declared here
/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward/strstream:160:9:
error: std::strstream::_ZTVSt9strstream.localalias.2 causes a section
type conflict with std::strstream::_ZTVSt9strstream
   class strstream : public basic_iostream<char>
         ^
/work/trunk-nightlies/builds/build-210913/armv7l-unknown-linux-gnueabihf/libstdc++-v3/include/backward/strstream:160:9:
note: _std::strstream::_ZTVSt9strstream_ was declared here


regards
Ramana


>
> Honza
>
>         * ipa-visibility.c (can_replace_by_local_alias_in_vtable): New function.
>         (update_vtable_references): New function.
>         (function_and_variable_visibility): Rewrite also vtable initializers.
>         * varpool.c (cgraph_variable_initializer_availability): Remove assert.
> Index: varpool.c
> ===================================================================
> --- varpool.c   (revision 210908)
> +++ varpool.c   (working copy)
> @@ -355,7 +355,6 @@ varpool_add_new_variable (tree decl)
>  enum availability
>  cgraph_variable_initializer_availability (varpool_node *node)
>  {
> -  gcc_assert (cgraph_function_flags_ready);
>    if (!node->definition)
>      return AVAIL_NOT_AVAILABLE;
>    if (!TREE_PUBLIC (node->decl))
> Index: ipa-visibility.c
> ===================================================================
> --- ipa-visibility.c    (revision 210908)
> +++ ipa-visibility.c    (working copy)
> @@ -343,6 +343,36 @@ can_replace_by_local_alias (symtab_node
>           && !symtab_can_be_discarded (node));
>  }
>
> +/* Return true if we can replace refernece to NODE by local alias
> +   within a virtual table.  Generally we can replace function pointers
> +   and virtual table pointers.  */
> +
> +bool
> +can_replace_by_local_alias_in_vtable (symtab_node *node)
> +{
> +  if (is_a <varpool_node *> (node)
> +      && !DECL_VIRTUAL_P (node->decl))
> +    return false;
> +  return can_replace_by_local_alias (node);
> +}
> +
> +/* walk_tree callback that rewrites initializer references.   */
> +
> +static tree
> +update_vtable_references (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
> +{
> +  if (TREE_CODE (*tp) == VAR_DECL
> +      || TREE_CODE (*tp) == FUNCTION_DECL)
> +    {
> +      if (can_replace_by_local_alias_in_vtable (symtab_get_node (*tp)))
> +       *tp = symtab_nonoverwritable_alias (symtab_get_node (*tp))->decl;
> +      *walk_subtrees = 0;
> +    }
> +  else if (IS_TYPE_OR_DECL_P (*tp))
> +    *walk_subtrees = 0;
> +  return NULL;
> +}
> +
>  /* In LTO we can remove COMDAT groups and weak symbols.
>     Either turn them into normal symbols or external symbol depending on
>     resolution info.  */
> @@ -625,6 +655,34 @@ function_and_variable_visibility (bool w
>           vnode->resolution = LDPR_PREVAILING_DEF_IRONLY;
>         }
>        update_visibility_by_resolution_info (vnode);
> +
> +      /* Update virutal tables to point to local aliases where possible.  */
> +      if (DECL_VIRTUAL_P (vnode->decl)
> +         && !DECL_EXTERNAL (vnode->decl))
> +       {
> +         int i;
> +         struct ipa_ref *ref;
> +         bool found = false;
> +
> +         /* See if there is something to update.  */
> +         for (i = 0; ipa_ref_list_referring_iterate (&vnode->ref_list,
> +                                                     i, ref); i++)
> +           if (ref->use == IPA_REF_ADDR
> +               && can_replace_by_local_alias_in_vtable (ref->referred))
> +             {
> +               found = true;
> +               break;
> +             }
> +         if (found)
> +           {
> +             struct pointer_set_t *visited_nodes = pointer_set_create ();
> +             walk_tree (&DECL_INITIAL (vnode->decl),
> +                        update_vtable_references, NULL, visited_nodes);
> +             pointer_set_destroy (visited_nodes);
> +             ipa_remove_all_references (&vnode->ref_list);
> +             record_references_in_initializer (vnode->decl, false);
> +           }
> +       }
>      }
>
>    if (dump_file)

On 05/25/2014 07:54 AM, Jan Hubicka wrote:
> Hi,
> this patch adds code to rerite references in vtable initializers to local aliases
> when doing so is a win.
>
> Bootstrapped/regtested x86_64-linux, comitted.
>
> Honza
>
> 	* ipa-visibility.c (can_replace_by_local_alias_in_vtable): New function.
> 	(update_vtable_references): New function.
> 	(function_and_variable_visibility): Rewrite also vtable initializers.
> 	* varpool.c (cgraph_variable_initializer_availability): Remove assert.
> Index: varpool.c
> ===================================================================
> --- varpool.c	(revision 210908)
> +++ varpool.c	(working copy)
> @@ -355,7 +355,6 @@ varpool_add_new_variable (tree decl)
>   enum availability
>   cgraph_variable_initializer_availability (varpool_node *node)
>   {
> -  gcc_assert (cgraph_function_flags_ready);
>     if (!node->definition)
>       return AVAIL_NOT_AVAILABLE;
>     if (!TREE_PUBLIC (node->decl))
> Index: ipa-visibility.c
> ===================================================================
> --- ipa-visibility.c	(revision 210908)
> +++ ipa-visibility.c	(working copy)
> @@ -343,6 +343,36 @@ can_replace_by_local_alias (symtab_node
>   	  && !symtab_can_be_discarded (node));
>   }
>   
> +/* Return true if we can replace refernece to NODE by local alias

Hello Jan,

s/refernece/reference

> +   within a virtual table.  Generally we can replace function pointers
> +   and virtual table pointers.  */
> +
> +bool
> +can_replace_by_local_alias_in_vtable (symtab_node *node)
> +{
> +  if (is_a <varpool_node *> (node)
> +      && !DECL_VIRTUAL_P (node->decl))
> +    return false;
> +  return can_replace_by_local_alias (node);
> +}
> +
> +/* walk_tree callback that rewrites initializer references.   */
> +
> +static tree
> +update_vtable_references (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
> +{
> +  if (TREE_CODE (*tp) == VAR_DECL
> +      || TREE_CODE (*tp) == FUNCTION_DECL)
> +    {
> +      if (can_replace_by_local_alias_in_vtable (symtab_get_node (*tp)))
> +	*tp = symtab_nonoverwritable_alias (symtab_get_node (*tp))->decl;
> +      *walk_subtrees = 0;
> +    }
> +  else if (IS_TYPE_OR_DECL_P (*tp))
> +    *walk_subtrees = 0;
> +  return NULL;
> +}
> +
>   /* In LTO we can remove COMDAT groups and weak symbols.
>      Either turn them into normal symbols or external symbol depending on
>      resolution info.  */
> @@ -625,6 +655,34 @@ function_and_variable_visibility (bool w
>   	  vnode->resolution = LDPR_PREVAILING_DEF_IRONLY;
>   	}
>         update_visibility_by_resolution_info (vnode);
> +
> +      /* Update virutal tables to point to local aliases where possible.  */
s/virutal/virtual

Martin
> +      if (DECL_VIRTUAL_P (vnode->decl)
> +	  && !DECL_EXTERNAL (vnode->decl))
> +	{
> +	  int i;
> +	  struct ipa_ref *ref;
> +	  bool found = false;
> +
> +	  /* See if there is something to update.  */
> +	  for (i = 0; ipa_ref_list_referring_iterate (&vnode->ref_list,
> +						      i, ref); i++)
> +	    if (ref->use == IPA_REF_ADDR
> +		&& can_replace_by_local_alias_in_vtable (ref->referred))
> +	      {
> +	        found = true;
> +		break;
> +	      }
> +	  if (found)
> +	    {
> +	      struct pointer_set_t *visited_nodes = pointer_set_create ();
> +	      walk_tree (&DECL_INITIAL (vnode->decl),
> +			 update_vtable_references, NULL, visited_nodes);
> +	      pointer_set_destroy (visited_nodes);
> +	      ipa_remove_all_references (&vnode->ref_list);
> +	      record_references_in_initializer (vnode->decl, false);
> +	    }
> +	}
>       }
>   
>     if (dump_file)