re PR middle-end/39500 (autopar fails to parallel)

2009-03-19  Li Feng  <nemokingdom@gmail.com>

	PR middle-end/39500
	* tree-data-ref.c (analyze_subscript_affine_affine): There is no
	dependence if the first conflict is after niter iterations.

testsuite/
	* gcc.dg/autopar/pr39500-1.c: New.
	* gcc.dg/autopar/pr39500-2.c: New.

From-SVN: r144952

gcc/ChangeLog

+2009-03-19  Li Feng  <nemokingdom@gmail.com>
+
+	PR middle-end/39500
+	* tree-data-ref.c (analyze_subscript_affine_affine): There is no
+	dependence if the first conflict is after niter iterations.
+
 2009-03-19  Hans-Peter Nilsson  <hp@axis.com>
 
 	PR middle-end/38609

gcc/testsuite/ChangeLog

+2009-03-19  Li Feng  <nemokingdom@gmail.com>
+
+	PR middle-end/39500
+	* gcc.dg/autopar/pr39500-1.c: New.
+	* gcc.dg/autopar/pr39500-2.c: New.
+
 2009-03-18  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* g++.dg/dg.exp: Prune graphite.

gcc/testsuite/gcc.dg/autopar/pr39500-1.c

+/* pr39500: autopar fails to parallel */
+/* origin: nemokingdom@gmail.com(LiFeng) */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-parallelize-loops=4 -fdump-tree-parloops-details" } */
+
+void abort (void);
+
+int main (void)
+{
+  int i;
+  int x[1000];
+
+  for (i = 0; i < 100; i++)
+    x[i] = x[i+100];
+
+  for (i = 0; i < 100; i++)
+    {
+      if (x[i] != x[i+100])
+       abort ();
+    }
+
+  return 0;
+}
+
+/* Check that the first loop in parloop got parallelized.  */
+
+/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 1 "parloops" } } */
+/* { dg-final { cleanup-tree-dump "parloops" } } */

gcc/testsuite/gcc.dg/autopar/pr39500-2.c

+/* pr39500: autopar fails to parallel */
+/* origin: nemokingdom@gmail.com(LiFeng) */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-parallelize-loops=4 -fdump-tree-parloops-details" } */
+
+int main (void)
+{
+  int i;
+  int x[1000];
+
+  for (i = 0; i < 101; i++)
+    x[i] = x[i+100];
+
+  return x[12];
+}
+
+/* This loop cannot be parallelized due to a dependence.  */
+
+/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 0 "parloops" } } */
+/* { dg-final { cleanup-tree-dump "parloops" } } */

gcc/tree-data-ref.c

@@ -2302,7 +2302,7 @@ analyze_subscript_affine_affine (tree chrec_a,
 
 		  /* If the overlap occurs outside of the bounds of the
 		     loop, there is no dependence.  */
-		  if (x1 > niter || y1 > niter)
+		  if (x1 >= niter || y1 >= niter)
 		    {
 		      *overlaps_a = conflict_fn_no_dependence ();
 		      *overlaps_b = conflict_fn_no_dependence ();