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?)

Author: tglsfdc

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
 		{
 			/*