Make amc obey shield invariants.

Copied from Perforce
 Change: 25379
 ServerID: perforce.ravenbrook.com

1 files changed, 9 insertions, 29 deletions

diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index b90d90dbc56..417d5cb455f 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -1397,7 +1397,6 @@ Res AMCFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
   RefSet summary;       /* summary of object being relocated */
   RefSet toSummary;     /* summary of object's destination */
   Seg toSeg;            /* segment to which object is being relocated */
-  Bool shieldUp;        /* whether we have exposed seg */
 
   /* design.mps.trace.fix.noaver */
   AVERT_CRITICAL(Pool, pool);
@@ -1441,13 +1440,9 @@ Res AMCFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
   AVER_CRITICAL(ref < SegLimit(seg));
   arena = pool->arena;
 
-  /* .access.read: Make sure seg isn't behind a read barrier. */
-  shieldUp = FALSE;
-  if (SegPM(seg) & AccessREAD) {
-    ShieldExpose(arena, seg);
-    shieldUp = TRUE;
-  }
+  ShieldExpose(arena, seg);
   newRef = (*format->isMoved)(ref);
+  ShieldCover(arena, seg);
 
   if (newRef == (Addr)0) {
     /* If object is nailed already then we mustn't copy it: */
@@ -1508,12 +1503,9 @@ Res AMCFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
     } while (!BUFFER_COMMIT(buffer, newRef, length));
     ss->copiedSize += length;
 
-    /* Make sure there's no read or write barrier. */
-    if (!shieldUp && (SegPM(seg) & (AccessWRITE | AccessREAD))) {
-      ShieldExpose(arena, seg);
-      shieldUp = TRUE;
-    }
+    ShieldExpose(arena, seg);
     (*format->move)(ref, newRef);
+    ShieldCover(arena, seg);
   } else {
     /* reference to broken heart (which should be snapped out -- */
     /* consider adding to (non-existant) snap-out cache here) */
@@ -1527,8 +1519,6 @@ updateReference:
   res = ResOK;
 
 returnRes:
-  if (shieldUp)
-    ShieldCover(arena, seg);
   return res;
 }
 
@@ -1554,7 +1544,6 @@ static Res AMCHeaderFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
   RefSet summary;       /* summary of object being relocated */
   RefSet toSummary;     /* summary of object's destination */
   Seg toSeg;            /* segment to which object is being relocated */
-  Bool shieldUp;        /* whether we have exposed seg */
 
   /* design.mps.trace.fix.noaver */
   AVERT_CRITICAL(Pool, pool);
@@ -1597,13 +1586,9 @@ static Res AMCHeaderFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
   AVER_CRITICAL(ref < SegLimit(seg)); /* see .ref-limit */
   arena = pool->arena;
 
-  /* .access.read.header: Make sure seg isn't behind a read barrier. */
-  shieldUp = FALSE;
-  if (SegPM(seg) & AccessREAD) {
-    ShieldExpose(arena, seg);
-    shieldUp = TRUE;
-  }
+  ShieldExpose(arena, seg);
   newRef = (*format->isMoved)(ref);
+  ShieldCover(arena, seg);
 
   if (newRef == (Addr)0) {
     /* If object is nailed already then we mustn't copy it: */
@@ -1667,12 +1652,9 @@ static Res AMCHeaderFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
     } while (!BUFFER_COMMIT(buffer, newBase, length));
     ss->copiedSize += length;
 
-    /* Make sure there's no read or write barrier. */
-    if (!shieldUp && (SegPM(seg) & (AccessWRITE | AccessREAD))) {
-      ShieldExpose(arena, seg);
-      shieldUp = TRUE;
-    }
+    ShieldExpose(arena, seg);
     (*format->move)(ref, newRef);
+    ShieldCover(arena, seg);
   } else {
     /* reference to broken heart (which should be snapped out -- */
     /* consider adding to (non-existent) snap-out cache here) */
@@ -1686,8 +1668,6 @@ updateReference:
   res = ResOK;
 
 returnRes:
-  if (shieldUp)
-    ShieldCover(arena, seg);
   return res;
 }
 
@@ -1967,7 +1947,7 @@ DEFINE_POOL_CLASS(AMCZPoolClass, this)
   this->grey = PoolNoGrey;
   this->scan = PoolNoScan;
 }
- 
+
 
 /* mps_class_amc -- return the pool class descriptor to the client */