Re: [PATCH] Fix PR66705

[Richard Biener <rguenther at suse dot de>]

On Wed, 2 Sep 2015, Richard Biener wrote:

> On Wed, 2 Sep 2015, Jan Hubicka wrote:
> 
> > > 
> > > 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).
> > 
> > Yep, you are correct that we don't currently have way to look into ctor
> > without actually loading. But do you need something more than just walking
> > references that you already have in ipa-ref lists?
> 
> Hmm, no, ipa-ref list should be enough (unless we start field-sensitive
> analysis or need NULL inits for correctness).  Still have to figure out
> how to walk the list and how the reference would look like (what
> is ref->use?  IPA_REF_ADDR?  can those be speculative?)

Sth like the following seems to work.

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)
@@ -5650,7 +5650,6 @@ 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))
@@ -5668,12 +5667,10 @@ create_variable_info_for_1 (tree decl, c
   /* Collect field information.  */
   if (use_field_sensitive
       && var_can_have_subvars (decl)
-      /* ???  Force us to not use subfields for global initializers
-	 in IPA mode.  Else we'd have to parse arbitrary initializers.  */
+      /* ???  Force us to not use subfields for globals 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 ()))
+	   && is_global_var (decl)))
     {
       fieldoff_s *fo = NULL;
       bool notokay = false;
@@ -5805,13 +5802,13 @@ 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)
+	  ipa_ref *ref;
+	  for (unsigned idx = 0; vnode->iterate_reference (idx, ref); ++idx)
 	    {
 	      auto_vec<ce_s> rhsc;
 	      struct constraint_expr lhs, *rhsp;
 	      unsigned i;
-	      get_constraint_for_rhs (vnode->get_constructor (), &rhsc);
+	      get_constraint_for_address_of (ref->referred->decl, &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;)
+      ;
+}