re PR tree-optimization/77605 (wrong code at -O3 on x86_64-linux-gnu)

2016-09-19  Richard Biener  <rguenther@suse.de>

	PR middle-end/77605
	* tree-data-ref.c (analyze_subscript_affine_affine): Use the
	proper niter to bound the loops.

	* gcc.dg/torture/pr77605.c: New testcase.

From-SVN: r240227

gcc/ChangeLog

 2016-09-19  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/77605
+	* tree-data-ref.c (analyze_subscript_affine_affine): Use the
+	proper niter to bound the loops.
+
+2016-09-19  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/77514
 	* tree-ssa-pre.c (create_expression_by_pieces): Optimize
 	search for folded stmt.

gcc/testsuite/ChangeLog

+2016-09-19  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/77605
+	* gcc.dg/torture/pr77605.c: New testcase.
+
 2016-09-18  Louis Krupp  <louis.krupp@zoho.com>
 
 	* gfortran.dg/pr68078.f90: XFAIL run on Darwin

gcc/testsuite/gcc.dg/torture/pr77605.c

+/* { dg-do run } */
+
+int a, b, c[2][8];
+
+int main ()
+{
+  for (a = 0; a < 8; a++)
+    for (b = 0; b < 2; b++)
+      c[b][a] = c[b][b + 6] ^ 1;
+
+  if (c[0][7] != 0) 
+    __builtin_abort ();
+
+  return 0; 
+}

gcc/tree-data-ref.c

@@ -2686,13 +2686,13 @@ analyze_subscript_affine_affine (tree chrec_a,
 
 	      if (niter > 0)
 		{
-		  HOST_WIDE_INT tau2 = MIN (FLOOR_DIV (niter - i0, i1),
-					    FLOOR_DIV (niter - j0, j1));
+		  HOST_WIDE_INT tau2 = MIN (FLOOR_DIV (niter_a - i0, i1),
+					    FLOOR_DIV (niter_b - j0, j1));
 		  HOST_WIDE_INT last_conflict = tau2 - (x1 - i0)/i1;
 
 		  /* If the overlap occurs outside of the bounds of the
 		     loop, there is no dependence.  */
-		  if (x1 >= niter || y1 >= niter)
+		  if (x1 >= niter_a || y1 >= niter_b)
 		    {
 		      *overlaps_a = conflict_fn_no_dependence ();
 		      *overlaps_b = conflict_fn_no_dependence ();