Add extra OPTIMIZATION-IF-FALSE comments where required to pcache.c.

FossilOrigin-Name: 9d55b8f541de43deb82d460d32005fd62f5430b2

1 files changed, 6 insertions, 3 deletions

diff --git a/src/pcache.c b/src/pcache.c
index ee7914a44..f8fe90177 100644
--- a/src/pcache.c
+++ b/src/pcache.c
@@ -424,8 +424,11 @@ void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
   if( (--p->nRef)==0 ){
     if( p->flags&PGHDR_CLEAN ){
       pcacheUnpin(p);
-    }else if( p->pDirtyPrev!=0 ){
-      /* Move the page to the head of the dirty list. */
+    }else if( p->pDirtyPrev!=0 ){ /*OPTIMIZATION-IF-FALSE*/
+      /* Move the page to the head of the dirty list. If p->pDirtyPrev==0,
+      ** then page p is already at the head of the dirty list and the
+      ** following call would be a no-op. Hence the OPTIMIZATION-IF-FALSE
+      ** tag above.  */
       pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
     }
   }
@@ -460,7 +463,7 @@ void sqlite3PcacheDrop(PgHdr *p){
 */
 void sqlite3PcacheMakeDirty(PgHdr *p){
   assert( p->nRef>0 );
-  if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){
+  if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){    /*OPTIMIZATION-IF-FALSE*/
     p->flags &= ~PGHDR_DONT_WRITE;
     if( p->flags & PGHDR_CLEAN ){
       p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN);