Fix partition WRT static variables taking address of labels

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
this patch fixes problem with partitioning WRT named labels.  This problem
reproduces with linux kernel LTO and also on firefox with -fno-toplevel-reorder
at least.

Bootstrapped/regtested x86_64-linux and tested it fixes the problem on Firefx,
intend to commit it tomorrow after some more testing on chromium

The patch may need a bit more tweaking WRT nested functions contains nonlocal
adresses taken, but that is even more exotic than the problem I am trying
to solve so I think it can wait for next stage1. This patch should be backportable
to earlier releases after reversing the C++ APi changes.

Honza

	PR lto/50676
	* symtab.c (symtab_node::get_partitioning_class): Local static
	taking named label inherits partitioning property of the function
	it belong to.
	* lto-cgraph.c (lto_output_varpool_node, input_varpool_node): Stream
	contains_named_label.
	* tree.c (decl_address_ip_invariant_p): LABEL_DECL is not IP
	invariant.
	* cgraph.h (varpool_node): Add contains_named_label.
	* cgraphbuild.c (record_reference): Record contains_named_label.
	* lto-partition.c (add_references_to_partition,
	add_symbol_to_partition_1): Local static var should stay in
	same partition as its containing function when it reffer to
	named label.
	(add_sorted_nodes): Skip static var referring named label.
	(lto_balanced_map): Likewise.
	* varpool.c (varpool_node::dump): Dump contains_named_label.
	* ipa.c (symbol_table::remove_unreachable_nodes): Variable
	referring named label keeps its function alive.

	* gcc.dg/lto/named-label.c: New testcase.
Index: symtab.c
===================================================================
--- symtab.c	(revision 221757)
+++ symtab.c	(working copy)
@@ -1682,6 +1682,11 @@ symtab_node::get_partitioning_class (voi
 
   if (varpool_node *vnode = dyn_cast <varpool_node *> (this))
     {
+      /* Static variables referring named label are always handled the same way
+	 as the function they belong to.  */
+      if (vnode->contains_named_label)
+	return cgraph_node::get (decl_function_context (decl))
+		->get_partitioning_class ();
       if (alias && definition && !ultimate_alias_target ()->definition)
 	return SYMBOL_EXTERNAL;
       /* Constant pool references use local symbol names that can not
Index: lto-cgraph.c
===================================================================
--- lto-cgraph.c	(revision 221757)
+++ lto-cgraph.c	(working copy)
@@ -662,6 +663,7 @@ lto_output_varpool_node (struct lto_simp
   bp_pack_value (&bp, node->tls_model, 3);
   bp_pack_value (&bp, node->used_by_single_function, 1);
   bp_pack_value (&bp, node->need_bounds_init, 1);
+  bp_pack_value (&bp, node->contains_named_label, 1);
   streamer_write_bitpack (&bp);
 
   group = node->get_comdat_group ();
@@ -1413,6 +1416,7 @@ input_varpool_node (struct lto_file_decl
   node->tls_model = (enum tls_model)bp_unpack_value (&bp, 3);
   node->used_by_single_function = (enum tls_model)bp_unpack_value (&bp, 1);
   node->need_bounds_init = bp_unpack_value (&bp, 1);
+  node->contains_named_label = bp_unpack_value (&bp, 1);
   group = read_identifier (ib);
   if (group)
     {
Index: tree.c
===================================================================
--- tree.c	(revision 221757)
+++ tree.c	(working copy)
@@ -3149,7 +3149,12 @@ decl_address_ip_invariant_p (const_tree
 
   switch (TREE_CODE (op))
     {
+    /* Theoretically label decls can be considered IP invariants, but until
+       we are able to handle them as regular symbols (i.e. output with
+       non-local visibility), we really want them to be contained in a function
+       they belong to.  */
     case LABEL_DECL:
+      return false;
     case FUNCTION_DECL:
     case STRING_CST:
       return true;
Index: cgraph.h
===================================================================
--- cgraph.h	(revision 221757)
+++ cgraph.h	(working copy)
@@ -1778,6 +1780,9 @@ public:
      if we did not do any inter-procedural code movement.  */
   unsigned used_by_single_function : 1;
 
+  /* Set if te variable is contains a named label.  */
+  unsigned contains_named_label : 1;
+
 private:
   /* Assemble thunks and aliases associated to varpool node.  */
   void assemble_aliases (void);
Index: cgraphbuild.c
===================================================================
--- cgraphbuild.c	(revision 221757)
+++ cgraphbuild.c	(working copy)
@@ -112,6 +112,8 @@ record_reference (tree *tp, int *walk_su
 	  varpool_node *vnode = varpool_node::get_create (decl);
 	  ctx->varpool_node->create_reference (vnode, IPA_REF_ADDR);
 	}
+      if (TREE_CODE (decl) == LABEL_DECL)
+	ctx->varpool_node->contains_named_label = true;
       *walk_subtrees = 0;
       break;
 
Index: lto/lto-partition.c
===================================================================
--- lto/lto-partition.c	(revision 221757)
+++ lto/lto-partition.c	(working copy)
@@ -113,6 +113,14 @@ add_references_to_partition (ltrans_part
   for (i = 0; node->iterate_reference (i, ref); i++)
     if (ref->referred->get_partitioning_class () == SYMBOL_DUPLICATE)
       add_symbol_to_partition (part, ref->referred);
+    /* A static variable referring to named labels must go to the same
+       partition as a function it belongs to.  */
+    else if (is_a <varpool_node *> (ref->referred)
+	     && (dyn_cast <varpool_node *> (ref->referred)
+		 ->contains_named_label)
+	     && node->decl == decl_function_context (ref->referred->decl)
+	     && !lto_symtab_encoder_in_partition_p (part->encoder, ref->referred))
+      add_symbol_to_partition (part, ref->referred);
     /* References to a readonly variable may be constant foled into its value.
        Recursively look into the initializers of the constant variable and add
        references, too.  */
@@ -193,6 +201,14 @@ add_symbol_to_partition_1 (ltrans_partit
 	add_symbol_to_partition_1 (part, cnode->instrumented_version);
     }
 
+  /* Variables referring named labels must always go to the same section
+     as the function they belong to.  */
+  if (is_a <varpool_node *> (node)
+      && dyn_cast <varpool_node *> (node)->contains_named_label)
+    add_symbol_to_partition_1 (part,
+			         cgraph_node::get
+				    (decl_function_context (node->decl)));
+
   add_references_to_partition (part, node);
 
   /* Add all aliases associated with the symbol.  */
@@ -409,7 +425,12 @@ add_sorted_nodes (vec<symtab_node *> &ne
 
   next_nodes.qsort (varpool_node_cmp);
   FOR_EACH_VEC_ELT (next_nodes, i, node)
-    if (!symbol_partitioned_p (node))
+    if (!symbol_partitioned_p (node)
+	/* Local statics containing named labels always go after their
+	   functions.  Do not partition on them and wait for them to be
+	   dragged in, so we do not force reordering of the functions.  */
+	&& (!is_a <varpool_node *> (node)
+	    || !dyn_cast <varpool_node *> (node)->contains_named_label))
       add_symbol_to_partition (partition, node);
 }
 
@@ -636,6 +657,7 @@ lto_balanced_map (int n_lto_partitions)
 		  continue;
 		if (!symbol_partitioned_p (vnode) && flag_toplevel_reorder
 		    && !vnode->no_reorder
+		    && !vnode->contains_named_label
 		    && vnode->get_partitioning_class () == SYMBOL_PARTITION)
 		  add_symbol_to_partition (partition, vnode);
 		index = lto_symtab_encoder_lookup (partition->encoder,
@@ -674,6 +696,7 @@ lto_balanced_map (int n_lto_partitions)
 		if (!symbol_partitioned_p (vnode) && flag_toplevel_reorder
 		    && !vnode->no_reorder
 		    && !vnode->can_remove_if_no_refs_p ()
+		    && !vnode->contains_named_label
 		    && vnode->get_partitioning_class () == SYMBOL_PARTITION)
 		  add_symbol_to_partition (partition, vnode);
 		index = lto_symtab_encoder_lookup (partition->encoder,
Index: varpool.c
===================================================================
--- varpool.c	(revision 221757)
+++ varpool.c	(working copy)
@@ -256,6 +256,8 @@ varpool_node::dump (FILE *f)
     fprintf (f, " const-value-known");
   if (writeonly)
     fprintf (f, " write-only");
+  if (contains_named_label)
+    fprintf (f, " contains-named-label");
   if (tls_model)
     fprintf (f, " tls-%s", tls_model_names [tls_model]);
   fprintf (f, "\n");
Index: ipa.c
===================================================================
--- ipa.c	(revision 221757)
+++ ipa.c	(working copy)
@@ -406,6 +406,18 @@ symbol_table::remove_unreachable_nodes (
 		      n->used_as_abstract_origin = true;
 		}
 	    }
+
+	  /* Static variables referring local label needs the containing
+	     function to be output.  */
+	  if (is_a <varpool_node *> (node)
+	      && dyn_cast <varpool_node *> (node)->contains_named_label)
+	    {
+	      cgraph_node *cn
+		 = cgraph_node::get (decl_function_context (node->decl));
+	      if (!reachable.add (cn))
+		enqueue_node (cn, &first, &reachable);
+	    }
+	      
 	  /* If any symbol in a comdat group is reachable, force
 	     all externally visible symbols in the same comdat
 	     group to be reachable as well.  Comdat-local symbols
Index: testsuite/gcc.dg/lto/named-label.c
===================================================================
--- testsuite/gcc.dg/lto/named-label.c	(revision 0)
+++ testsuite/gcc.dg/lto/named-label.c	(revision 0)
@@ -0,0 +1,29 @@
+/* { dg-lto-do link } */
+/* { dg-lto-options { { -fPIC -flto -flto-partition=max } } } */
+void *p0,*p1;
+void test (void **p)
+{
+  if (p[0]==p[1])
+    __builtin_abort ();
+  p0=p[0];
+  p1=p[1];
+}
+void test2 (void **p)
+{
+  if (p[0]!=p0|| p[1] !=p1)
+    __builtin_abort ();
+}
+void ** t()
+{
+  static void * labelptr[2]={&&label, &&label2};
+label:
+  test (labelptr);
+label2:
+  return labelptr;
+}
+int
+main()
+{
+  void **labelptr = t();
+  test2 (labelptr);
+}