mem: Support any number of master-IDs in stride prefetcher

The stride prefetcher had a hardcoded number of contexts (i.e. master-IDs)
that it could handle. Since master IDs need to be unique per system, and
every core, cache etc. requires a separate master port, a static limit on
these does not make much sense.

Instead, this patch adds a small hash map that will map all master IDs to
the right prefetch state and dynamically allocates new state for new master
IDs.

1 files changed, 24 insertions, 13 deletions

diff --git a/src/mem/cache/prefetch/stride.cc b/src/mem/cache/prefetch/stride.cc
index 74c84b94f..bcd72f25a 100644
--- a/src/mem/cache/prefetch/stride.cc
+++ b/src/mem/cache/prefetch/stride.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2013 ARM Limited
+ * Copyright (c) 2012-2013, 2015 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -59,27 +59,40 @@ StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p)
       pcTableAssoc(p->table_assoc),
       pcTableSets(p->table_sets),
       useMasterId(p->use_master_id),
-      degree(p->degree)
+      degree(p->degree),
+      pcTable(pcTableAssoc, pcTableSets, name())
 {
     // Don't consult stride prefetcher on instruction accesses
     onInst = false;
 
     assert(isPowerOf2(pcTableSets));
+}
 
-    for (int c = 0; c < maxContexts; c++) {
-        pcTable[c] = new StrideEntry*[pcTableSets];
-        for (int s = 0; s < pcTableSets; s++) {
-            pcTable[c][s] = new StrideEntry[pcTableAssoc];
-        }
+StridePrefetcher::StrideEntry**
+StridePrefetcher::PCTable::allocateNewContext(int context)
+{
+    auto res = entries.insert(std::make_pair(context,
+                              new StrideEntry*[pcTableSets]));
+    auto it = res.first;
+    chatty_assert(res.second, "Allocating an already created context\n");
+    assert(it->first == context);
+
+    DPRINTF(HWPrefetch, "Adding context %i with stride entries at %p\n",
+            context, it->second);
+
+    StrideEntry** entry = it->second;
+    for (int s = 0; s < pcTableSets; s++) {
+        entry[s] = new StrideEntry[pcTableAssoc];
     }
+    return entry;
 }
 
-StridePrefetcher::~StridePrefetcher()
-{
-    for (int c = 0; c < maxContexts; c++) {
+StridePrefetcher::PCTable::~PCTable() {
+    for (auto entry : entries) {
         for (int s = 0; s < pcTableSets; s++) {
-            delete[] pcTable[c][s];
+            delete[] entry.second[s];
         }
+        delete[] entry.second;
     }
 }
 
@@ -98,8 +111,6 @@ StridePrefetcher::calculatePrefetch(const PacketPtr &pkt,
     bool is_secure = pkt->isSecure();
     MasterID master_id = useMasterId ? pkt->req->masterId() : 0;
 
-    assert(master_id < maxContexts);
-
     // Lookup pc-based information
     StrideEntry *entry;