re PR tree-optimization/46886 (wrong code with -ftree-parallelize-loops -fno-tree-ch)

2012-03-08  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/46886
	* tree-flow.h (do_while_loop_p): Declare.
	* tree-ssa-loop-ch.c (do_while_loop_p): Export.
	* tree-parloops.c (parallelize_loops): Only parallelize do-while
	loops.

	* testsuite/libgomp.c/pr46886.c: New testcase.

From-SVN: r184010

gcc/ChangeLog

@@ -1,3 +1,11 @@
+2012-02-08  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/46886
+	* tree-flow.h (do_while_loop_p): Declare.
+	* tree-ssa-loop-ch.c (do_while_loop_p): Export.
+	* tree-parloops.c (parallelize_loops): Only parallelize do-while
+	loops.
+
 2012-02-08  Andrew MacLeod  <amacleod@redhat.com>
 
 	* optabs.c (expand_atomic_load): Do not assume compare_and_swap will

gcc/tree-flow.h

@@ -619,6 +619,9 @@ extern bool may_propagate_copy (tree, tree);
 extern bool may_propagate_copy_into_stmt (gimple, tree);
 extern bool may_propagate_copy_into_asm (tree);
 
+/* In tree-ssa-loop-ch.c  */
+bool do_while_loop_p (struct loop *);
+
 /* Affine iv.  */
 
 typedef struct

gcc/tree-parloops.c

@@ -2183,7 +2183,10 @@ parallelize_loops (void)
 	  || loop_has_blocks_with_irreducible_flag (loop)
 	  || (loop_preheader_edge (loop)->src->flags & BB_IRREDUCIBLE_LOOP)
 	  /* FIXME: the check for vector phi nodes could be removed.  */
-	  || loop_has_vector_phi_nodes (loop))
+	  || loop_has_vector_phi_nodes (loop)
+	  /* FIXME: transform_to_exit_first_loop does not handle not
+	     header-copied loops correctly - see PR46886.  */
+	  || !do_while_loop_p (loop))
 	continue;
       estimated = max_stmt_executions_int (loop, false);
       /* FIXME: Bypass this check as graphite doesn't update the

gcc/tree-ssa-loop-ch.c

@@ -104,7 +104,7 @@ should_duplicate_loop_header_p (basic_block header, struct loop *loop,
 
 /* Checks whether LOOP is a do-while style loop.  */
 
-static bool
+bool
 do_while_loop_p (struct loop *loop)
 {
   gimple stmt = last_stmt (loop->latch);

libgomp/ChangeLog

@@ -1,3 +1,8 @@
+2012-02-08  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/46886
+	* testsuite/libgomp.c/pr46886.c: New testcase.
+
 2012-01-25  Matthias Klose  <doko@ubuntu.com>
 
 	* config/linux/arm: Remove empty directory.

libgomp/testsuite/libgomp.c/pr46886.c

@@ -0,0 +1,28 @@
+/* { dg-do run } */
+/* { dg-options "-O -ftree-parallelize-loops=4 -fno-tree-ch -fno-tree-dominator-opts" } */
+
+void abort(void);
+
+int d[1024], e[1024];
+
+int foo (void)
+{
+  int s = 0;
+  int i;
+  for (i = 0; i < 1024; i++)
+    s += d[i] - e[i];
+  return s;
+}
+
+int main ()
+{
+  int i;
+  for (i = 0; i < 1024; i++)
+    {
+      d[i] = i * 2;
+      e[i] = i;
+    }
+  if (foo () != 1023 * 1024 / 2)
+    abort ();
+  return 0;
+}