Mps br/diag: start to demonstrate job001658 defect:

Show that after finding one RankFINAL segment, traceFindGrey then 
goes back to RankEXACT segs before tracing the next RankFINAL segment.

Copied from Perforce
 Change: 162626
 ServerID: perforce.ravenbrook.com

mps/code/fint1658.c

@@ -20,9 +20,6 @@
  * The modifications are to make lots of guardians, such that they 
  * don't all fit on one segment, in order to test for the (suspected) 
  * finalization promptness defect described in job001658.
- *
- *****  NOTE: It doesn't do that yet!  Currently it's just a copy of 
- *****  finalcv.c.  RHSK 2007-06-21
  */
 
 #include "testlib.h"
@@ -39,7 +36,11 @@
 
 
 #define testArenaSIZE   ((size_t)16<<20)
-#define rootCOUNT 20
+
+/* usually (ArenaAlign / sizeof(Ref)) = 1024 */
+/* so choose 2050 to force 3 segments of guardians */
+#define rootCOUNT 2050
+
 #define churnFACTOR 10
 #define finalizationRATE 6
 #define gcINTERVAL ((size_t)150 * 1024)

mps/code/poolmrg.c

@@ -634,6 +634,9 @@ static Res MRGInit(Pool pool, va_list args)
   mrg->sig = MRGSig;
 
   AVERT(MRG, mrg);
+  DIAG_PRINTF(( "mrg->extendBy = %u, MRGGuardiansPerSeg = %u\n", 
+                (unsigned int) mrg->extendBy, 
+                (unsigned int) MRGGuardiansPerSeg(mrg) ));
   EVENT_PPP(PoolInit, pool, PoolArena(pool), ClassOfPool(pool));
   return ResOK;
 }

mps/code/trace.c

@@ -993,8 +993,36 @@ static void traceReclaim(Trace trace)
  * which does not have a higher rank than any other such segment (i.e.,
  * a next segment to scan).  */
 
+static Bool traceFindGreyORIGINAL(Seg *segReturn, Rank *rankReturn,
+                                  Arena arena, TraceId ti);
+/* wrap debugging around original traceFindGrey */
 static Bool traceFindGrey(Seg *segReturn, Rank *rankReturn,
                           Arena arena, TraceId ti)
+{
+  Bool found;
+  char this;
+
+  found = traceFindGreyORIGINAL(segReturn, rankReturn, arena, ti);
+
+  this = !found ? '0'
+         : (*rankReturn == RankAMBIG) ? 'A'
+         : (*rankReturn == RankEXACT) ? 'E'
+         : (*rankReturn == RankFINAL) ? 'F'
+         : (*rankReturn == RankWEAK) ? 'W'
+         : '?';
+
+  DIAG_PRINTF(( "%c", this ));
+  if(!found) {
+    /* that's the end of the trace */
+    DIAG_PRINTF(( "\n" ));
+  }
+  
+  return found;
+}
+
+/* original traceFindGrey */
+static Bool traceFindGreyORIGINAL(Seg *segReturn, Rank *rankReturn,
+                                  Arena arena, TraceId ti)
 {
   Rank rank;
   Trace trace;