[arm-embedded] [PATCH, GCC/LTO, ping] Fix PR69866: LTO with def for weak alias in regular object file

[Thomas Preudhomme]

Hi,

We have decided to apply the forwarded patch to the embedded-7-branch to fix an 
ICE when doing partial LTO with weak symbols.

ChangeLog entry is as follows:

2017-11-28  Thomas Preud'homme  <thomas.preudho...@arm.com>

        Backport from mainline
        2017-06-15  Jan Hubicka  <hubi...@ucw.cz>
                    Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR lto/69866
        * lto-symtab.c (lto_symtab_merge_symbols): Drop useless definitions
        that resolved externally.

        Backport from mainline
        2017-06-15  Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR lto/69866
        * gcc.dg/lto/pr69866_0.c: New test.
        * gcc.dg/lto/pr69866_1.c: Likewise.


Best regards,

Thomas
--- Begin Message ---
Hi,
I am testing the following. Let me know if it works for you.

Honza

Index: lto/lto-symtab.c
===================================================================
--- lto/lto-symtab.c    (revision 249213)
+++ lto/lto-symtab.c    (working copy)
@@ -952,6 +952,42 @@
              if (tgt)
                node->resolve_alias (tgt, true);
            }
+         /* If the symbol was preempted outside IR, see if we want to get rid
+            of the definition.  */
+         if (node->analyzed
+             && !DECL_EXTERNAL (node->decl)
+             && (node->resolution == LDPR_PREEMPTED_REG
+                 || node->resolution == LDPR_RESOLVED_IR
+                 || node->resolution == LDPR_RESOLVED_EXEC
+                 || node->resolution == LDPR_RESOLVED_DYN))
+           {
+             DECL_EXTERNAL (node->decl) = 1;
+             /* If alias to local symbol was preempted by external definition,
+                we know it is not pointing to the local symbol.  Remove it.  */
+             if (node->alias
+                 && !node->weakref
+                 && !node->transparent_alias
+                 && node->get_alias_target ()->binds_to_current_def_p ())
+               {
+                 node->alias = false;
+                 node->remove_all_references ();
+                 node->definition = false;
+                 node->analyzed = false;
+                 node->cpp_implicit_alias = false;
+               }
+             else if (!node->alias
+                      && node->definition
+                      && node->get_availability () <= AVAIL_INTERPOSABLE)
+               {
+                 if ((cnode = dyn_cast <cgraph_node *> (node)) != NULL)
+                   cnode->reset ();
+                 else
+                   {
+                     node->analyzed = node->definition = false;
+                     node->remove_all_references ();
+                   }
+               }
+           }
 
          if (!(cnode = dyn_cast <cgraph_node *> (node))
              || !cnode->clone_of
--- End Message ---