Fix TYPE_MAIN_VARIANT made by ipa-prop

[Jan Hubicka]

Hi,
according to my type checker, ipa-prop is only place where we produce a variant 
of
a METHOD_TYPE that is FUNCTION_TYPE or viarant that has different parameters.

The code in question is producing new prototype to remove unused arguments,
but I do not think it should eclare the new type to be variant of the original.

Historically I think I introduced the code because I simply copied what linker
does without caring too much about the consequences.

Bootstrapped/regtested x86_64-linux, OK?

        * ipa-prop.c (ipa_modify_formal_parameters): Do not declare new type
        to be variant of original type.

Index: ipa-prop.c
===================================================================
--- ipa-prop.c  (revision 215615)
+++ ipa-prop.c  (working copy)
@@ -3990,21 +3990,6 @@
       DECL_FUNCTION_CODE (fndecl) = (enum built_in_function) 0;
     }
 
-  /* This is a new type, not a copy of an old type.  Need to reassociate
-     variants.  We can handle everything except the main variant lazily.  */
-  tree t = TYPE_MAIN_VARIANT (orig_type);
-  if (orig_type != t)
-    {
-      TYPE_MAIN_VARIANT (new_type) = t;
-      TYPE_NEXT_VARIANT (new_type) = TYPE_NEXT_VARIANT (t);
-      TYPE_NEXT_VARIANT (t) = new_type;
-    }
-  else
-    {
-      TYPE_MAIN_VARIANT (new_type) = new_type;
-      TYPE_NEXT_VARIANT (new_type) = NULL;
-    }
-
   TREE_TYPE (fndecl) = new_type;
   DECL_VIRTUAL_P (fndecl) = 0;
   DECL_LANG_SPECIFIC (fndecl) = NULL;