Tweak the tree descent loop in fsm_search_avail to not look at the

right child if it doesn't need to.  This saves some miniscule number
of cycles, but the ulterior motive is to avoid an optimization bug
known to exist in SCO's C compiler (and perhaps others?)

diff --git a/src/backend/storage/freespace/fsmpage.c b/src/backend/storage/freespace/fsmpage.c
index 3a25c959299bf574f8c3900f4cbee8cb6a5ff7ae..a4479e88c075dce8bbcaad03ea08a5859750966d 100644 (file)
--- a/src/backend/storage/freespace/fsmpage.c
+++ b/src/backend/storage/freespace/fsmpage.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/storage/freespace/fsmpage.c,v 1.2 2008/10/07 21:10:11 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/storage/freespace/fsmpage.c,v 1.3 2008/12/10 17:11:18 tgl Exp $
  *
  * NOTES:
  *
@@ -243,17 +243,20 @@ fsm_search_avail(Buffer buf, uint8 minvalue, bool advancenext,
     */
    while (nodeno < NonLeafNodesPerPage)
    {
-       int leftnodeno = leftchild(nodeno);
-       int rightnodeno = leftnodeno + 1;
-       bool leftok = (leftnodeno < NodesPerPage) &&
-           (fsmpage->fp_nodes[leftnodeno] >= minvalue);
-       bool rightok = (rightnodeno < NodesPerPage) &&
-           (fsmpage->fp_nodes[rightnodeno] >= minvalue);
-
-       if (leftok)
-           nodeno = leftnodeno;
-       else if (rightok)
-           nodeno = rightnodeno;
+       int childnodeno = leftchild(nodeno);
+
+       if (childnodeno < NodesPerPage &&
+           fsmpage->fp_nodes[childnodeno] >= minvalue)
+       {
+           nodeno = childnodeno;
+           continue;
+       }
+       childnodeno++;          /* point to right child */
+       if (childnodeno < NodesPerPage &&
+           fsmpage->fp_nodes[childnodeno] >= minvalue)
+       {
+           nodeno = childnodeno;
+       }
        else
        {
            /*