[PATCH] predict_loop fix (PR tree-optimization/48189)

[Jakub Jelinek]

Hi!

This is Steven's patch from the PR plus mine hunk, bootstrapped/regtested on
x86_64-linux and i686-linux, ok for trunk?

2013-01-08  Steven Bosscher  <ste...@gcc.gnu.org>
            Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/48189
        * predict.c (predict_loops): If max is 0, don't call compare_tree_int.
        If nitercst is 0, don't predict the exit edge.

        * gcc.dg/pr48189.c: New test.

--- gcc/predict.c.jj    2013-01-04 13:44:35.000000000 +0100
+++ gcc/predict.c       2013-01-08 15:58:15.552884491 +0100
@@ -1434,7 +1434,8 @@ predict_loops (void)
          if (TREE_CODE (niter) == INTEGER_CST)
            {
              if (host_integerp (niter, 1)
-                 && compare_tree_int (niter, max-1) == -1)
+                 && max
+                 && compare_tree_int (niter, max - 1) == -1)
                nitercst = tree_low_cst (niter, 1) + 1;
              else
                nitercst = max;
@@ -1456,6 +1457,11 @@ predict_loops (void)
          else
            continue;
 
+         /* If the prediction for number of iterations is zero, do not
+            predict the exit edges.  */
+         if (nitercst == 0)
+           continue;
+
          probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst);
          predict_edge (ex, predictor, probability);
        }
--- gcc/testsuite/gcc.dg/pr48189.c.jj   2013-01-08 15:59:38.319433008 +0100
+++ gcc/testsuite/gcc.dg/pr48189.c      2013-01-08 15:52:31.000000000 +0100
@@ -0,0 +1,13 @@
+/* PR tree-optimization/48189 */
+/* { dg-do compile } */
+/* { dg-options "-O --param max-predicted-iterations=0" } */
+
+struct S { int s[8]; };
+  
+void
+foo (int *x, struct S *y)
+{
+  int i;
+  for (i = 0; y[i].s[i]; i++)
+    *x++ = y[i].s[i];
+}

        Jakub