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

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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?)
This commit is contained in:
Tom Lane 2008-12-10 17:11:18 +00:00
parent 253fa736b9
commit 55368223cd
1 changed files with 14 additions and 11 deletions
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25
src/backend/storage/freespace/fsmpage.c
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@ -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);
int childnodeno = leftchild(nodeno);
if (leftok)
nodeno = leftnodeno;
else if (rightok)
nodeno = rightnodeno;
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
{
/*