alias.c (record_component_aliases): Do not simplify pointed-to types of ODR types

	* alias.c (record_component_aliases): Do not simplify pointed-to
	types of ODR types 
	* testsuite/g++.dg/lto/alias-4_0.C

From-SVN: r273552

gcc/ChangeLog

+2019-07-17  Jan Hubicka  <hubicka@ucw.cz>
+
+	* alias.c (record_component_aliases): Do not simplify pointed-to
+	types of ODR types 
+
 2019-07-17  Uroš Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.md (*andqi_2_maybe_si): Handle potential

gcc/alias.c

@@ -1202,10 +1202,8 @@ record_component_aliases (tree type)
     case RECORD_TYPE:
     case UNION_TYPE:
     case QUAL_UNION_TYPE:
-      for (field = TYPE_FIELDS (type); field != 0; field = DECL_CHAIN (field))
-	if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
       {
-	    /* LTO type merging does not make any difference between 
+	/* LTO non-ODR type merging does not make any difference between 
 	   component pointer types.  We may have
 
 	   struct foo {int *a;};
@@ -1223,8 +1221,14 @@ record_component_aliases (tree type)
 	   void * is special cased and works as a universal pointer type.
 	   Accesses to it conflicts with accesses to any other pointer
 	   type.  */
+	bool void_pointers = in_lto_p
+			     && (!odr_type_p (type)
+				 || !odr_based_tbaa_p (type));
+	for (field = TYPE_FIELDS (type); field != 0; field = DECL_CHAIN (field))
+	  if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
+	    {
 	      tree t = TREE_TYPE (field);
-	    if (in_lto_p)
+	      if (void_pointers)
 		{
 		  /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
 		     element type and that type has to be normalized to void *,
@@ -1243,6 +1247,7 @@ record_component_aliases (tree type)
 
 	      record_alias_subset (superset, get_alias_set (t));
 	    }
+      }
       break;
 
     case COMPLEX_TYPE:

gcc/testsuite/ChangeLog

+2019-07-17  Jan Hubicka  <hubicka@ucw.cz>
+
+	* g++.dg/lto/alias-4_0.C
+
 2019-07-17  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/91178

gcc/testsuite/g++.dg/lto/alias-4_0.C

+/* { dg-lto-do run } */
+/* { dg-lto-options { { -O3 -flto -fno-early-inlining } } } */
+__attribute__ ((used))
+short *ptr_init, **ptr=&ptr_init;
+
+__attribute__ ((used))
+struct a {
+  int *aptr;
+} a, *aptr=&a;
+
+void
+write_ptr ()
+{
+  *aptr = a;
+}
+
+__attribute__ ((used))
+void
+test ()
+{
+  *ptr = (short int *)0;
+  write_ptr ();
+  if (!__builtin_constant_p (*ptr == (void *)0))
+    __builtin_abort ();
+}
+int
+main()
+{
+  test ();
+  return 0;
+}