* predict.c (estimate_probability): Fix roundoff error.

From-SVN: r62765

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b81e4c8..4597565 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+Wed Feb 12 15:19:42 CET 2003  Jan Hubicka  <jh@suse.cz>
+
+       * predict.c (estimate_probability):  Fix roundoff error.
+
 2003-02-12  Kazu Hirata  <kazu@cs.umass.edu>
 
        * config/h8300/h8300.md (a peephole2): Don't handle 65535.

diff --git a/gcc/predict.c b/gcc/predict.c
index b0170f3..a0fc75a 100644 (file)
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -449,14 +449,19 @@ estimate_probability (loops_info)
       if (simple_loop_p (loops_info, loop, &desc)
          && desc.const_iter)
        {
+         int prob;
          niter = desc.niter + 1;
          if (niter == 0)        /* We might overflow here.  */
            niter = desc.niter;
 
+         prob = (REG_BR_PROB_BASE
+                 - (REG_BR_PROB_BASE + niter /2) / niter);
+         /* Branch prediction algorithm gives 0 frequency for everything
+            after the end of loop for loop having 0 probability to finish.  */
+         if (prob == REG_BR_PROB_BASE)
+           prob = REG_BR_PROB_BASE - 1;
          predict_edge (desc.in_edge, PRED_LOOP_ITERATIONS,
-                       REG_BR_PROB_BASE
-                       - (REG_BR_PROB_BASE + niter /2)
-                       / niter);
+                       prob);
        }
 
       bbs = get_loop_body (loop);