Prevent merging across COMDAT group boundary

[Jan Hubicka]

Hi,
tihs patch fixes one case I forgot in sem_function::merge: When target is not
in comdat group, we still can not make alias in the case source is.

Bootstrapped/regtested x86_64-linux, Martin, can you double check this fixes the xalancbmk?

Honza

	PR ipa/65237
	* ipa-icf.c (sem_function::merge): Do not attempt to produce alias
	across COMDAT group boundary.

Index: ipa-icf.c
===================================================================
--- ipa-icf.c	(revision 221076)
+++ ipa-icf.c	(working copy)
@@ -745,12 +755,17 @@ sem_function::merge (sem_item *alias_ite
 	it is an external functions where we can not create an alias
 	(ORIGINAL_DISCARDABLE)
      3) if target do not support symbol aliases.
+     4) original and alias lie in different comdat groups.
 
      If we can not produce alias, we will turn ALIAS into WRAPPER of ORIGINAL
      and/or redirect all callers from ALIAS to ORIGINAL.  */
   if ((original_address_matters && alias_address_matters)
-      || original_discardable
-      || !sem_item::target_supports_symbol_aliases_p ())
+      || (original_discardable
+	  && (!DECL_COMDAT_GROUP (alias->decl)
+	      || (DECL_COMDAT_GROUP (alias->decl)
+		  != DECL_COMDAT_GROUP (original->decl))))
+      || !sem_item::target_supports_symbol_aliases_p ()
+      || DECL_COMDAT_GROUP (alias->decl) != DECL_COMDAT_GROUP (original->decl))
     {
       /* First see if we can produce wrapper.  */