[PATCH] Fix PR64530

[Richard Biener]

This fixes PR64530 by fixing a mistake (oops) in the iteration
over all data-ref pairs in pg_add_dependence_edges.

Bootstrap and regtest pending on x86_64-unknown-linux-gnu.

Richard.

2015-01-12  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/64530
	* tree-loop-distribution.c (pg_add_dependence_edges): Shuffle
	back dr1.

	* gfortran.dg/pr64530.f90: New testcase.

Index: gcc/tree-loop-distribution.c
===================================================================
--- gcc/tree-loop-distribution.c	(revision 219446)
+++ gcc/tree-loop-distribution.c	(working copy)
@@ -1362,6 +1375,7 @@ pg_add_dependence_edges (struct graph *r
   for (int ii = 0; drs1.iterate (ii, &dr1); ++ii)
     for (int jj = 0; drs2.iterate (jj, &dr2); ++jj)
       {
+	data_reference_p saved_dr1 = dr1;
 	int this_dir = 1;
 	ddr_p ddr;
 	/* Re-shuffle data-refs to be in dominator order.  */
@@ -1407,6 +1421,8 @@ pg_add_dependence_edges (struct graph *r
 	  dir = this_dir;
 	else if (dir != this_dir)
 	  return 2;
+	/* Shuffle "back" dr1.  */
+	dr1 = saved_dr1;
       }
   return dir;
 }
Index: gcc/testsuite/gfortran.dg/pr64530.f90
===================================================================
--- gcc/testsuite/gfortran.dg/pr64530.f90	(revision 0)
+++ gcc/testsuite/gfortran.dg/pr64530.f90	(working copy)
@@ -0,0 +1,38 @@
+! { dg-do run }
+
+program bug
+  ! Bug triggered with at least three elements
+  integer, parameter :: asize = 3
+
+  double precision,save :: ave(asize)
+  double precision,save :: old(asize)
+  double precision,save :: tmp(asize)
+
+  ave(:) = 10.d0
+  old(:) = 3.d0
+  tmp(:) = 0.d0
+
+  call buggy(2.d0,asize,ave,old,tmp)
+  if (any (tmp(:) .ne. 3.5)) call abort
+end
+
+subroutine buggy(scale_factor, asize, ave, old, tmp)
+
+  implicit none
+  ! Args
+  double precision scale_factor
+  integer asize
+  double precision ave(asize)
+  double precision old(asize)
+  double precision tmp(asize)
+
+  ! Local 
+  integer i
+
+  do i = 1, asize
+    tmp(i) = ave(i) - old(i)
+    old(i) = ave(i)
+    tmp(i) = tmp(i) / scale_factor
+  end do
+
+end subroutine buggy