Force prefetches to check cache and MSHRs immediately prior to issue.

This prevents redundant prefetches from being issued, solving the
occasional 'needsExclusive && !blk->isWritable()' assertion failure
in cache_impl.hh that several people have run into.
Eliminates "prefetch_cache_check_push" flag, neither setting of
which really solved the problem.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh
index 80b7c545c..d8630c1f5 100644
--- a/src/mem/cache/cache_impl.hh
+++ b/src/mem/cache/cache_impl.hh
@@ -1301,11 +1301,14 @@ Cache<TagStore>::getNextMSHR()
         // If we have a miss queue slot, we can try a prefetch
         PacketPtr pkt = prefetcher->getPacket();
         if (pkt) {
-            // Update statistic on number of prefetches issued
-            // (hwpf_mshr_misses)
-            mshr_misses[pkt->cmdToIndex()][0/*pkt->req->threadId()*/]++;
-            // Don't request bus, since we already have it
-            return allocateMissBuffer(pkt, curTick, false);
+            Addr pf_addr = blockAlign(pkt->getAddr());
+            if (!tags->findBlock(pf_addr) && !mshrQueue.findMatch(pf_addr)) {
+                // Update statistic on number of prefetches issued
+                // (hwpf_mshr_misses)
+                mshr_misses[pkt->cmdToIndex()][0/*pkt->req->threadId()*/]++;
+                // Don't request bus, since we already have it
+                return allocateMissBuffer(pkt, curTick, false);
+            }
         }
     }