Improve TBAA for types in anonymous namespaces

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
this patch adjusts LTO tree merging to treat anonymous namespace types
as local to a given TU, so just like !TREE_PUBLIC decls they are not
merged (this is unify_scc change). This makes them to get different
canonical types and act as independent types for TBAA.

I also modified canonical type calculation to never consider anonymous
namespace types as interoperable with structurally equivalent types
declared in non-C++ translation units.

Both these changes are tested by the testcase (first change makes set1
and set2 independent and second chnage makes set1&set2 independent of
set3).

lto-bootstrapped/regtested x86_64-linux
Honza

	* lto-common.c (gimple_register_canonical_type_1): Do not look for
	non-ODR conflicts of types in anonymous namespaces.
	(unify_scc): Do not merge anonymous namespace types.
	* g++.dg/lto/alias-5_0.C: New testcase.
	* g++.dg/lto/alias-5_1.C: New.
	* g++.dg/lto/alias-5_2.c: New.
Index: lto/lto-common.c
===================================================================
--- lto/lto-common.c	(revision 273551)
+++ lto/lto-common.c	(working copy)
@@ -418,13 +418,19 @@ gimple_register_canonical_type_1 (tree t
   if (RECORD_OR_UNION_TYPE_P (t)
       && odr_type_p (t) && !odr_type_violation_reported_p (t))
     {
-      /* Here we rely on fact that all non-ODR types was inserted into
-	 canonical type hash and thus we can safely detect conflicts between
-	 ODR types and interoperable non-ODR types.  */
-      gcc_checking_assert (type_streaming_finished
-			   && TYPE_MAIN_VARIANT (t) == t);
-      slot = htab_find_slot_with_hash (gimple_canonical_types, t, hash,
-				       NO_INSERT);
+      /* Anonymous namespace types never conflict with non-C++ types.  */
+      if (type_with_linkage_p (t) && type_in_anonymous_namespace_p (t))
+	slot = NULL;
+      else
+	{
+	  /* Here we rely on fact that all non-ODR types was inserted into
+	     canonical type hash and thus we can safely detect conflicts between
+	     ODR types and interoperable non-ODR types.  */
+	  gcc_checking_assert (type_streaming_finished
+			       && TYPE_MAIN_VARIANT (t) == t);
+	  slot = htab_find_slot_with_hash (gimple_canonical_types, t, hash,
+					   NO_INSERT);
+	}
       if (slot && !TYPE_CXX_ODR_P (*(tree *)slot))
 	{
 	  tree nonodr = *(tree *)slot;
@@ -1640,11 +1646,14 @@ unify_scc (class data_in *data_in, unsig
       tree t = streamer_tree_cache_get_tree (cache, from + i);
       scc->entries[i] = t;
       /* Do not merge SCCs with local entities inside them.  Also do
-	 not merge TRANSLATION_UNIT_DECLs.  */
+	 not merge TRANSLATION_UNIT_DECLs and anonymous namespace types.  */
       if (TREE_CODE (t) == TRANSLATION_UNIT_DECL
 	  || (VAR_OR_FUNCTION_DECL_P (t)
 	      && !(TREE_PUBLIC (t) || DECL_EXTERNAL (t)))
-	  || TREE_CODE (t) == LABEL_DECL)
+	  || TREE_CODE (t) == LABEL_DECL
+	  || (TYPE_P (t)
+	      && type_with_linkage_p (TYPE_MAIN_VARIANT (t))
+	      && type_in_anonymous_namespace_p (TYPE_MAIN_VARIANT (t))))
 	{
 	  /* Avoid doing any work for these cases and do not worry to
 	     record the SCCs for further merging.  */
Index: testsuite/g++.dg/lto/alias-5_0.C
===================================================================
--- testsuite/g++.dg/lto/alias-5_0.C	(nonexistent)
+++ testsuite/g++.dg/lto/alias-5_0.C	(working copy)
@@ -0,0 +1,35 @@
+/* { dg-lto-do run } */
+/* { dg-lto-options { { -O3 -flto } } } */
+/* This testcase tests that anonymous namespaces in different TUs are treated
+   as different types by LTO TBAA and that they never alias with structurally
+   same C types.  */
+namespace {
+  __attribute__((used))
+  struct a {int a;} *p,**ptr=&p;
+};
+void
+set1()
+{
+  *ptr=0;
+}
+void
+get1()
+{
+  if (!__builtin_constant_p (*ptr==0))
+    __builtin_abort ();
+}
+extern void set2();
+extern "C" void set3();
+int n = 1;
+int
+main()
+{
+  for (int i = 0; i < n; i++)
+    {
+      set1();
+      set2();
+      set3();
+      get1();
+    }
+  return 0;
+}
Index: testsuite/g++.dg/lto/alias-5_1.C
===================================================================
--- testsuite/g++.dg/lto/alias-5_1.C	(nonexistent)
+++ testsuite/g++.dg/lto/alias-5_1.C	(working copy)
@@ -0,0 +1,9 @@
+namespace {
+  __attribute__((used))
+  struct a {int a;} *p,**ptr=&p,q;
+};
+void
+set2()
+{
+  *ptr=&q;
+}
Index: testsuite/g++.dg/lto/alias-5_2.c
===================================================================
--- testsuite/g++.dg/lto/alias-5_2.c	(nonexistent)
+++ testsuite/g++.dg/lto/alias-5_2.c	(working copy)
@@ -0,0 +1,7 @@
+  __attribute__((used))
+  struct a {int a;} *p,**ptr=&p,q;
+void
+set3()
+{
+  *ptr=&q;
+}