From 7776ff6176109fdcc5113b8b0eaa01f04ff66aa7 Mon Sep 17 00:00:00 2001
From: Richard Kistruck <rhsk@ravenbrook.com>
Date: Thu, 23 Aug 2007 17:50:31 +0100
Subject: [PATCH] Mps master: poolamc.c amcfix, amcheaderfix: correct bad
 shield

code (but badness was being masked by the shield cache; see
job001706).  ShieldExpose(seg) once, and ShieldCover it once, so
that _all_ .exposed.seg statements are between Expose and Cover.

Copied from Perforce
 Change: 163171
 ServerID: perforce.ravenbrook.com
---
 mps/code/poolamc.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index c4fbf8f46a3..7ab6e5b9875 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -1656,11 +1656,10 @@ Res AMCFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
   AVER_CRITICAL(ref < SegLimit(seg));
   arena = pool->arena;
 
-  /* .exposed.seg: statements tagged ".exposed.seg" below require */
+  /* .exposed.seg: Statements tagged ".exposed.seg" below require */
   /* that "seg" (that is: the 'from' seg) has been ShieldExposed. */
   ShieldExpose(arena, seg);
   newRef = (*format->isMoved)(ref);  /* .exposed.seg */
-  ShieldCover(arena, seg);  /* .exposed.seg */
 
   if(newRef == (Addr)0) {
     /* If object is nailed already then we mustn't copy it: */
@@ -1724,9 +1723,7 @@ Res AMCFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
     } while(!BUFFER_COMMIT(buffer, newRef, length));
     ss->copiedSize += length;
 
-    ShieldExpose(arena, seg);
     (*format->move)(ref, newRef);  /* .exposed.seg */
-    ShieldCover(arena, seg);
   } else {
     /* reference to broken heart (which should be snapped out -- */
     /* consider adding to (non-existant) snap-out cache here) */
@@ -1740,6 +1737,7 @@ updateReference:
   res = ResOK;
 
 returnRes:
+  ShieldCover(arena, seg);  /* .exposed.seg */
   return res;
 }
 
@@ -1809,11 +1807,10 @@ static Res AMCHeaderFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
   AVER_CRITICAL(ref < SegLimit(seg)); /* see .ref-limit */
   arena = pool->arena;
 
-  /* .exposed.seg: statements tagged ".exposed.seg" below require */
+  /* .exposed.seg: Statements tagged ".exposed.seg" below require */
   /* that "seg" (that is: the 'from' seg) has been ShieldExposed. */
   ShieldExpose(arena, seg);
   newRef = (*format->isMoved)(ref);  /* .exposed.seg */
-  ShieldCover(arena, seg);  /* .exposed.seg */
 
   if(newRef == (Addr)0) {
     /* If object is nailed already then we mustn't copy it: */
@@ -1877,9 +1874,7 @@ static Res AMCHeaderFix(Pool pool, ScanState ss, Seg seg, Ref *refIO)
     } while (!BUFFER_COMMIT(buffer, newBase, length));
     ss->copiedSize += length;
 
-    ShieldExpose(arena, seg);
     (*format->move)(ref, newRef);  /* .exposed.seg */
-    ShieldCover(arena, seg);
   } else {
     /* reference to broken heart (which should be snapped out -- */
     /* consider adding to (non-existent) snap-out cache here) */
@@ -1893,6 +1888,7 @@ updateReference:
   res = ResOK;
 
 returnRes:
+  ShieldCover(arena, seg);  /* .exposed.seg */
   return res;
 }