unroll-1.c: New testcase.

	* gcc.dg/tree-prof/unroll-1.c: New testcase.

	* loop-unroll.c (decide_unroll_constant_iterations): Don't
	perform unrolling for loops with low iterations bounds or estimates.

From-SVN: r192638

gcc/ChangeLog

 2012-10-20  Jan Hubicka  <jh@suse.cz>
 
+	* loop-unroll.c (decide_unroll_constant_iterations): Don't
+	perform unrolling for loops with low iterations bounds or estimates.
+
+2012-10-20  Jan Hubicka  <jh@suse.cz>
+
 	* loop-iv.c (iv_number_of_iterations): Record the upper bound
 	only if there are no further conditions on it.
 

gcc/loop-unroll.c

@@ -519,6 +519,7 @@ decide_unroll_constant_iterations (struct loop *loop, int flags)
 {
   unsigned nunroll, nunroll_by_av, best_copies, best_unroll = 0, n_copies, i;
   struct niter_desc *desc;
+  double_int iterations;
 
   if (!(flags & UAP_UNROLL))
     {
@@ -561,8 +562,14 @@ decide_unroll_constant_iterations (struct loop *loop, int flags)
       return;
     }
 
-  /* Check whether the loop rolls enough to consider.  */
-  if (desc->niter < 2 * nunroll)
+  /* Check whether the loop rolls enough to consider.  
+     Consult also loop bounds and profile; in the case the loop has more
+     than one exit it may well loop less than determined maximal number
+     of iterations.  */
+  if (desc->niter < 2 * nunroll
+      || ((estimated_loop_iterations (loop, &iterations)
+	   || max_loop_iterations (loop, &iterations))
+	  && iterations.ult (double_int::from_shwi (2 * nunroll))))
     {
       if (dump_file)
 	fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");

gcc/testsuite/ChangeLog

+2012-10-20  Jan Hubicka  <jh@suse.cz>
+
+	* gcc.dg/tree-prof/unroll-1.c: New testcase.
+
 2012-10-19  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/54224

gcc/testsuite/gcc.dg/tree-prof/unroll-1.c

+/* { dg-options "-O3 -fdump-rtl-loop2_unroll -funroll-loops -fno-peel-loops" } */
+void abort ();
+
+int a[1000];
+int
+__attribute__ ((noinline))
+t()
+{
+  int i;
+  for (i=0;i<1000;i++)
+    if (!a[i])
+      return 1;
+  abort ();
+}
+main()
+{
+  int i;
+  for (i=0;i<1000;i++)
+    t();
+  return 0;
+}
+/* { dg-final-use { scan-rtl-dump "Considering unrolling loop with constant number of iterations" "loop2_unroll" } } */
+/* { dg-final-use { cleanup-rtl-dump "Not unrolling loop, doesn't roll" } } */
+/* { dg-options "-O3 -fdump-rtl-loop2_unroll -funroll-loops -fno-peel-loops" } */