re PR tree-optimization/64530 (Incorrect calculation when assigning to array with -O3)

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.

From-SVN: r219474

gcc/ChangeLog

 2015-01-12  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/64530
+	* tree-loop-distribution.c (pg_add_dependence_edges): Shuffle
+	back dr1.
+
+2015-01-12  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/64357
 	* tree-cfg.c (gimple_can_merge_blocks_p): Protect simple
 	latches properly.

gcc/testsuite/ChangeLog

 2015-01-12  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/64530
+	* gfortran.dg/pr64530.f90: New testcase.
+
+2015-01-12  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/64357
 	* gcc.dg/torture/pr64357.c: New testcase.
 

gcc/testsuite/gfortran.dg/pr64530.f90

+! { 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

gcc/tree-loop-distribution.c

@@ -1362,6 +1362,7 @@ pg_add_dependence_edges (struct graph *rdg, vec<loop_p> loops, int dir,
   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 +1408,8 @@ pg_add_dependence_edges (struct graph *rdg, vec<loop_p> loops, int dir,
 	  dir = this_dir;
 	else if (dir != this_dir)
 	  return 2;
+	/* Shuffle "back" dr1.  */
+	dr1 = saved_dr1;
       }
   return dir;
 }