[PATCH][4.4] Fix PR42773

[Richard Guenther <rguenther at suse dot de>]

This fixes PR42773 a regression from 4.4.2 caused by a wrong way
to check for the existance of PHI nodes.  It seems to be a common
pattern, so I'll go over the rest in the 4.5 tree.

Bootstrap and testing running on x86_64-unknown-linux-gnu,
ok for 4.4.3?

Thanks,
Richard.

2010-01-17  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/42773
	* tree-ssa-pre.c (phi_translate_set): Fix check for PHI node existance.
	(compute_antic_aux): Likewise.
	(compute_partial_antic_aux): Likewise.

	* g++.dg/torture/pr42773.C: New testcase.

Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c	(revision 155978)
--- gcc/tree-ssa-pre.c	(working copy)
*************** phi_translate_set (bitmap_set_t dest, bi
*** 1718,1724 ****
    pre_expr expr;
    int i;
  
!   if (!phi_nodes (phiblock))
      {
        bitmap_set_copy (dest, set);
        return;
--- 1718,1724 ----
    pre_expr expr;
    int i;
  
!   if (gimple_seq_empty_p (phi_nodes (phiblock)))
      {
        bitmap_set_copy (dest, set);
        return;
*************** compute_antic_aux (basic_block block, bo
*** 2100,2113 ****
  	  goto maybe_dump_sets;
  	}
  
!       if (phi_nodes (first))
  	phi_translate_set (ANTIC_OUT, ANTIC_IN (first), block, first);
        else
  	bitmap_set_copy (ANTIC_OUT, ANTIC_IN (first));
  
        for (i = 0; VEC_iterate (basic_block, worklist, i, bprime); i++)
  	{
! 	  if (phi_nodes (bprime))
  	    {
  	      bitmap_set_t tmp = bitmap_set_new ();
  	      phi_translate_set (tmp, ANTIC_IN (bprime), block, bprime);
--- 2100,2113 ----
  	  goto maybe_dump_sets;
  	}
  
!       if (!gimple_seq_empty_p (phi_nodes (first)))
  	phi_translate_set (ANTIC_OUT, ANTIC_IN (first), block, first);
        else
  	bitmap_set_copy (ANTIC_OUT, ANTIC_IN (first));
  
        for (i = 0; VEC_iterate (basic_block, worklist, i, bprime); i++)
  	{
! 	  if (!gimple_seq_empty_p (phi_nodes (bprime)))
  	    {
  	      bitmap_set_t tmp = bitmap_set_new ();
  	      phi_translate_set (tmp, ANTIC_IN (bprime), block, bprime);
*************** compute_partial_antic_aux (basic_block b
*** 2257,2263 ****
  	      FOR_EACH_EXPR_ID_IN_SET (ANTIC_IN (bprime), i, bi)
  		bitmap_value_insert_into_set (PA_OUT,
  					      expression_for_id (i));
! 	      if (phi_nodes (bprime))
  		{
  		  bitmap_set_t pa_in = bitmap_set_new ();
  		  phi_translate_set (pa_in, PA_IN (bprime), block, bprime);
--- 2257,2263 ----
  	      FOR_EACH_EXPR_ID_IN_SET (ANTIC_IN (bprime), i, bi)
  		bitmap_value_insert_into_set (PA_OUT,
  					      expression_for_id (i));
! 	      if (!gimple_seq_empty_p (phi_nodes (bprime)))
  		{
  		  bitmap_set_t pa_in = bitmap_set_new ();
  		  phi_translate_set (pa_in, PA_IN (bprime), block, bprime);
Index: gcc/testsuite/g++.dg/torture/pr42773.C
===================================================================
*** gcc/testsuite/g++.dg/torture/pr42773.C	(revision 0)
--- gcc/testsuite/g++.dg/torture/pr42773.C	(revision 0)
***************
*** 0 ****
--- 1,54 ----
+ // { dg-do compile }
+ // { dg-options "-fno-exceptions" }
+ 
+ typedef unsigned int uint;
+ struct QShared {
+     bool deref() {
+ 	return !--count;
+     }
+     uint count;
+ };
+ template <class T> class QValueListNode {
+ public:
+     QValueListNode<T>* next;
+     QValueListNode<T>* prev;
+ };
+ template <class T> class QValueListPrivate : public QShared {
+ public:
+     typedef QValueListNode<T> Node;
+     typedef QValueListNode<T>* NodePtr;
+     QValueListPrivate();
+     void derefAndDelete()     {
+ 	if ( deref() )      delete this;
+     }
+     ~QValueListPrivate();
+     NodePtr node;
+ };
+ template <class T>  QValueListPrivate<T>::QValueListPrivate() {
+     node = new Node;
+     node->next = node->prev = node;
+ }
+ template <class T>  QValueListPrivate<T>::~QValueListPrivate() {
+     NodePtr p = node->next;
+     while( p != node ) {
+ 	NodePtr x = p->next;
+ 	delete p;
+ 	p = x;
+     }
+ }
+ template <class T> class QValueList {
+ public:
+     QValueList() {
+ 	sh = new QValueListPrivate<T>;
+     }
+     ~QValueList() {
+ 	sh->derefAndDelete();
+     }
+     QValueListPrivate<T>* sh;
+ };
+ class Cell {
+     QValueList<Cell*> obscuringCells() const;
+ };
+ QValueList<Cell*> Cell::obscuringCells() const {
+     QValueList<Cell*> empty;
+ }