[Bug bootstrap/46055] [4.6 Regression] -fwhopr failed configure test

["hubicka at ucw dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46055

--- Comment #10 from Jan Hubicka <hubicka at ucw dot cz> 2010-10-18 15:11:52 UTC ---
Hi,
I found what is causing the problem.  I accidentally comitted also the
following cleanup of visibility code.  The difference is that we now trust
linker's LDPR_PREVAILING_DEF_IRONLY and bring symbols local when they are
declared so even without default visibility.

Linker should not declare symbols that can be bound by dynamic linker
as LDPR_PREVAILING_DEF_IRONLY (according to my earlier conversation about
COMDATs).  I am looking into it and will either revert the patch today or
add missing changelog (and post to ML).
Sorry for that.

Honza

Index: ipa.c
===================================================================
*** ipa.c    (revision 165562)
--- ipa.c    (working copy)
*************** cgraph_externally_visible_p (struct cgra
*** 595,600 ****
--- 608,630 ----
    /* If linker counts on us, we must preserve the function.  */
    if (cgraph_used_from_object_file_p (node))
      return true;
+   if (DECL_PRESERVE_P (node->decl))
+     return true;
+   if (lookup_attribute ("externally_visible", DECL_ATTRIBUTES (node->decl)))
+     return true;
+ 
+   /* See if we have linker information about symbol not being used or
+      if we need to make guess based on the declaration.
+ 
+      Even if the linker clams the symbol is unused, never bring internal
+      symbols that are declared by user as used or externally visible.
+      This is needed for i.e. references from asm statements.   */
+   for (alias = node->same_body; alias; alias = alias->next)
+     if (alias->resolution != LDPR_PREVAILING_DEF_IRONLY)
+       break;
+   if (!alias && node->resolution == LDPR_PREVAILING_DEF_IRONLY)
+     return false;
+ 
    /* When doing link time optimizations, hidden symbols become local.  */
    if (in_lto_p
        && (DECL_VISIBILITY (node->decl) == VISIBILITY_HIDDEN
*************** cgraph_externally_visible_p (struct cgra
*** 626,636 ****
            return true;
      }
      }
!   if (DECL_PRESERVE_P (node->decl))
!     return true;
    if (MAIN_NAME_P (DECL_NAME (node->decl)))
      return true;
!   if (lookup_attribute ("externally_visible", DECL_ATTRIBUTES (node->decl)))
      return true;
    return false;
  }
--- 656,725 ----
            return true;
      }
      }
! 
    if (MAIN_NAME_P (DECL_NAME (node->decl)))
      return true;
! 
!   return false;
! }
! 
! /* Return true when variable VNODE should be considered externally visible. 
*/
! 
! static bool
! varpool_externally_visible_p (struct varpool_node *vnode, bool aliased)
! {
!   struct varpool_node *alias;
!   if (!DECL_COMDAT (vnode->decl) && !TREE_PUBLIC (vnode->decl))
!     return false;
! 
!   /* Do not even try to be smart about aliased nodes.  Until we properly
!      represent everything by same body alias, these are just evil.  */
!   if (aliased)
!     return true;
! 
!   /* If linker counts on us, we must preserve the function.  */
!   if (varpool_used_from_object_file_p (vnode))
!     return true;
! 
!   if (DECL_PRESERVE_P (vnode->decl))
!     return true;
!   if (lookup_attribute ("externally_visible",
!             DECL_ATTRIBUTES (vnode->decl)))
!     return true;
! 
!   /* See if we have linker information about symbol not being used or
!      if we need to make guess based on the declaration.
! 
!      Even if the linker clams the symbol is unused, never bring internal
!      symbols that are declared by user as used or externally visible.
!      This is needed for i.e. references from asm statements.   */
!   if (varpool_used_from_object_file_p (vnode))
!     return true;
!   for (alias = vnode->extra_name; alias; alias = alias->next)
!     if (alias->resolution != LDPR_PREVAILING_DEF_IRONLY)
!       break;
!   if (!alias && vnode->resolution == LDPR_PREVAILING_DEF_IRONLY)
!     return false;
! 
!   /* When doing link time optimizations, hidden symbols become local.  */
!   if (in_lto_p
!       && (DECL_VISIBILITY (vnode->decl) == VISIBILITY_HIDDEN
!       || DECL_VISIBILITY (vnode->decl) == VISIBILITY_INTERNAL)
!       /* Be sure that node is defined in IR file, not in other object
!      file.  In that case we don't set used_from_other_object_file.  */
!       && vnode->finalized)
!     ;
!   else if (!flag_whole_program)
!     return true;
! 
!   /* Do not attempt to privatize COMDATS by default.
!      This would break linking with C++ libraries sharing
!      inline definitions.
! 
!      FIXME: We can do so for readonly vars with no address taken and
!      possibly also for vtables since no direct pointer comparsion is done.
!      It might be interesting to do so to reduce linking overhead.  */
!   if (DECL_COMDAT (vnode->decl) || DECL_WEAK (vnode->decl))
      return true;
    return false;
  }
*************** function_and_variable_visibility (bool w
*** 786,812 ****
        if (!vnode->finalized)
          continue;
        if (vnode->needed
!       && (DECL_COMDAT (vnode->decl) || TREE_PUBLIC (vnode->decl))
!       && (((!whole_program
!             /* We can privatize comdat readonly variables whose address is
!            not taken, but doing so is not going to bring us
!            optimization oppurtunities until we start reordering
!            datastructures.  */
!         || DECL_COMDAT (vnode->decl)
!         || DECL_WEAK (vnode->decl))
!            /* When doing linktime optimizations, all hidden symbols will
!           become local.  */
!            && (!in_lto_p
!            || (DECL_VISIBILITY (vnode->decl) != VISIBILITY_HIDDEN
!                && DECL_VISIBILITY (vnode->decl) != VISIBILITY_INTERNAL)
!            /* We can get prevailing decision in other object file.
!               In this case we do not sed used_from_object_file.  */
!            || !vnode->finalized))
!           || DECL_PRESERVE_P (vnode->decl)
!               || varpool_used_from_object_file_p (vnode)
!           || pointer_set_contains (aliased_vnodes, vnode)
!           || lookup_attribute ("externally_visible",
!                    DECL_ATTRIBUTES (vnode->decl))))
      vnode->externally_visible = true;
        else
          vnode->externally_visible = false;
--- 875,883 ----
        if (!vnode->finalized)
          continue;
        if (vnode->needed
!       && varpool_externally_visible_p
!           (vnode, 
!            pointer_set_contains (aliased_vnodes, vnode)))
      vnode->externally_visible = true;
        else
          vnode->externally_visible = false;