mem-cache: ReplacementPolicy specific replacement data

Replacement data is specific for each replacement policy, and thus
should be instantiated differently by each policy.

Touch() and reset() do not need to be aware of CacheBlk, as they
only update its ReplacementData.

Invalidate() makes replacement policies independent of cache blocks,
by removing the awareness of the valid state.

An inheritable base ReplaceableEntry class was created to allow usage
of replacement policies with any table-like structure.

Change-Id: I998917d800fa48504ed95abffa2f1b7bfd68522b
Reviewed-on: https://gem5-review.googlesource.com/9421
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

1 files changed, 38 insertions, 14 deletions

diff --git a/src/mem/cache/replacement_policies/lfu_rp.cc b/src/mem/cache/replacement_policies/lfu_rp.cc
index 90a5ee227..ffa653e87 100644
--- a/src/mem/cache/replacement_policies/lfu_rp.cc
+++ b/src/mem/cache/replacement_policies/lfu_rp.cc
@@ -30,36 +30,60 @@
 
 #include "mem/cache/replacement_policies/lfu_rp.hh"
 
-#include "debug/CacheRepl.hh"
+#include <memory>
 
 LFURP::LFURP(const Params *p)
     : BaseReplacementPolicy(p)
 {
 }
 
-CacheBlk*
-LFURP::getVictim(const ReplacementCandidates& candidates)
+void
+LFURP::invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
+const
+{
+    // Reset reference count
+    std::static_pointer_cast<LFUReplData>(replacement_data)->refCount = 0;
+}
+
+void
+LFURP::touch(const std::shared_ptr<ReplacementData>& replacement_data) const
+{
+    // Update reference count
+    std::static_pointer_cast<LFUReplData>(replacement_data)->refCount++;
+}
+
+void
+LFURP::reset(const std::shared_ptr<ReplacementData>& replacement_data) const
+{
+    // Reset reference count
+    std::static_pointer_cast<LFUReplData>(replacement_data)->refCount = 1;
+}
+
+ReplaceableEntry*
+LFURP::getVictim(const ReplacementCandidates& candidates) const
 {
     // There must be at least one replacement candidate
     assert(candidates.size() > 0);
 
     // Visit all candidates to find victim
-    CacheBlk* blk = candidates[0];
+    ReplaceableEntry* victim = candidates[0];
     for (const auto& candidate : candidates) {
-        // Stop iteration if found an invalid block
-        if (!candidate->isValid()) {
-            blk = candidate;
-            break;
-        // Update victim block if necessary
-        } else if (candidate->refCount < blk->refCount) {
-            blk = candidate;
+        // Update victim entry if necessary
+        if (std::static_pointer_cast<LFUReplData>(
+                    candidate->replacementData)->refCount <
+                std::static_pointer_cast<LFUReplData>(
+                    victim->replacementData)->refCount) {
+            victim = candidate;
         }
     }
 
-    DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
-            blk->set, blk->way);
+    return victim;
+}
 
-    return blk;
+std::shared_ptr<ReplacementData>
+LFURP::instantiateEntry()
+{
+    return std::shared_ptr<ReplacementData>(new LFUReplData());
 }
 
 LFURP*