[PATCH] Fix PR66705

[Richard Biener <rguenther@suse.de>]

I was naiively using ->get_constructor in IPA PTA without proper
checking on wheter that succeeds.  Now I tried to use ctor_for_folding
but that isn't good as we want to analyze non-const globals in IPA
PTA and we need to analyze their initialiers as well.

Thus I'm trying below with ctor_for_analysis, but I really "just"
need the initializer or a "not available" for conservative handling.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Honza - I suppose you should doble-check this and suggest sth
different (or implement sth more generic in the IPA infrastructure).

Thanks,
Richard.

2015-09-02  Richard Biener  <rguenther@suse.de>

	PR ipa/66705
	* tree-ssa-structalias.c (ctor_for_analysis): New function.
	(create_variable_info_for_1): Use ctor_for_analysis instead
	of get_constructor.
	(create_variable_info_for): Likewise.

	* g++.dg/lto/pr66705_0.C: New testcase.

Index: gcc/tree-ssa-structalias.c
===================================================================
--- gcc/tree-ssa-structalias.c	(revision 227207)
+++ gcc/tree-ssa-structalias.c	(working copy)
@@ -5637,6 +5637,26 @@ check_for_overlaps (vec<fieldoff_s> fiel
   return false;
 }
 
+/* We can't use ctor_for_folding as that only returns constant constructors.  */
+
+static tree
+ctor_for_analysis (tree decl)
+{
+  varpool_node *node = varpool_node::get (decl);
+  if (!node)
+    return error_mark_node;
+  node = node->ultimate_alias_target ();
+  if (DECL_INITIAL (node->decl) != error_mark_node
+      || !in_lto_p)
+    return (DECL_INITIAL (node->decl)
+	    ? DECL_INITIAL (node->decl) : error_mark_node);
+  if (in_lto_p
+      && node->lto_file_data
+      && !node->body_removed)
+    return node->get_constructor ();
+  return error_mark_node;
+}
+
 /* Create a varinfo structure for NAME and DECL, and add it to VARMAP.
    This will also create any varinfo structures necessary for fields
    of DECL.  */
@@ -5650,7 +5670,6 @@ create_variable_info_for_1 (tree decl, c
   auto_vec<fieldoff_s> fieldstack;
   fieldoff_s *fo;
   unsigned int i;
-  varpool_node *vnode;
 
   if (!declsize
       || !tree_fits_uhwi_p (declsize))
@@ -5672,8 +5691,7 @@ create_variable_info_for_1 (tree decl, c
 	 in IPA mode.  Else we'd have to parse arbitrary initializers.  */
       && !(in_ipa_mode
 	   && is_global_var (decl)
-	   && (vnode = varpool_node::get (decl))
-	   && vnode->get_constructor ()))
+	   && ctor_for_analysis (decl) != error_mark_node))
     {
       fieldoff_s *fo = NULL;
       bool notokay = false;
@@ -5805,13 +5823,13 @@ create_variable_info_for (tree decl, con
 
 	  /* If this is a global variable with an initializer and we are in
 	     IPA mode generate constraints for it.  */
-	  if (vnode->get_constructor ()
-	      && vnode->definition)
+	  tree ctor = ctor_for_analysis (decl);
+	  if (ctor != error_mark_node)
 	    {
 	      auto_vec<ce_s> rhsc;
 	      struct constraint_expr lhs, *rhsp;
 	      unsigned i;
-	      get_constraint_for_rhs (vnode->get_constructor (), &rhsc);
+	      get_constraint_for_rhs (ctor, &rhsc);
 	      lhs.var = vi->id;
 	      lhs.offset = 0;
 	      lhs.type = SCALAR;
Index: gcc/testsuite/g++.dg/lto/pr66705_0.C
===================================================================
--- gcc/testsuite/g++.dg/lto/pr66705_0.C	(revision 0)
+++ gcc/testsuite/g++.dg/lto/pr66705_0.C	(working copy)
@@ -0,0 +1,15 @@
+// { dg-lto-do link }
+// { dg-lto-options { { -O2 -flto -flto-partition=max -fipa-pta } } }
+// { dg-extra-ld-options "-r -nostdlib" }
+
+class A {
+public:
+    A();
+};
+int a = 0;
+void foo() {
+    a = 0;
+    A b;
+    for (; a;)
+      ;
+}