re PR tree-optimization/18815 (Tree if-conversion screws up cfg very badly)

       PR tree-optimization/18815
       * tree-if-conv.c (combine_blocks): Adjust loop header edges for
       loops with zero exit edges.

From-SVN: r95796

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e5e19ccd4939db7519f8050571c3d82c01b84608..a4aced01cdd08f13b188390cf060c8fa22167602 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2005-03-02  Devang Patel  <dpatel@apple.com>
+
+       PR tree-optimization/18815
+       * tree-if-conv.c (combine_blocks): Adjust loop header edges for
+       loops with zero exit edges.
+       
 2005-03-02  Kazu Hirata  <kazu@cs.umass.edu>
 
        * cfg.c (connect_src, connect_dest, disconnect_src,

diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index bb832d2461668d2d61b50e3b64b698918bd0e9d1..ce66e2a7bbce2956f45db26a446847c9d1136a40 100644 (file)
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -905,11 +905,22 @@ combine_blocks (struct loop *loop)
        continue;
 
       /* It is time to remove this basic block.         First remove edges.  */
-      while (EDGE_COUNT (bb->succs) > 0)
-       remove_edge (EDGE_SUCC (bb, 0));
       while (EDGE_COUNT (bb->preds) > 0)
        remove_edge (EDGE_PRED (bb, 0));
 
+      /* This is loop latch and loop does not have exit then do not
+        delete this basic block. Just remove its PREDS and reconnect 
+        loop->header and loop->latch blocks.  */
+      if (bb == loop->latch && loop->num_exits == 0)
+       {
+         make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
+         set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
+         continue;
+       }
+
+      while (EDGE_COUNT (bb->succs) > 0)
+       remove_edge (EDGE_SUCC (bb, 0));
+
       /* Remove labels and make stmts member of loop->header.  */
       for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
        {