mem: cache: tags: Implement FIFO Cache Replacement Policy

Signed-off-by: Ranjeet Kumar <rkumar15@hawk.iit.edu>

configs/learning_gem5/part1/caches.py

@@ -96,7 +96,7 @@ class L1DCache(L1Cache):
                     help="L1 data cache associativity. Default: %s" % assoc)
     SimpleOpts.add_option('--replacement_policy',
                     help="L1 cache replacement policy. [NMRU,LFU,LIFO,LRU,"
-                         "Random]")
+                         "Random,FIFO]")
 
     def __init__(self, opts=None):
         super(L1DCache, self).__init__(opts)
@@ -124,6 +124,9 @@ class L1DCache(L1Cache):
         elif opts.replacement_policy == "LIFO":
             from m5.objects import LIFO
             self.tags = LIFO()
+        elif opts.replacement_policy == "FIFO":
+            from m5.objects import FIFO
+            self.tags = FIFO()
         elif opts.replacement_policy:
             fatal("Unsupported replacement policy: %s" %
                   opts.replacement_policy)

src/mem/cache/tags/SConscript

@@ -40,3 +40,4 @@ Source('fa_lru.cc')
 Source('nmru.cc')
 Source('lfu.cc')
 Source('lifo.cc')
+Source('fifo.cc')

src/mem/cache/tags/Tags.py

@@ -95,3 +95,7 @@ class LIFO(BaseSetAssoc):
     type = 'LIFO'
     cxx_class = 'LIFO'
     cxx_header = "mem/cache/tags/lifo.hh"
+class FIFO(BaseSetAssoc):
+    type = 'FIFO'
+    cxx_class = 'FIFO'
+    cxx_header = "mem/cache/tags/fifo.hh"

src/mem/cache/tags/fifo.cc

@@ -0,0 +1,74 @@
+/*
+ * Authors: Ranjeet Kumar
+ */
+
+/**
+ * @file
+ * Definitions of a FIFO tag store.
+ */
+
+#include "mem/cache/tags/fifo.hh"
+
+#include "debug/CacheRepl.hh"
+#include "mem/cache/base.hh"
+
+FIFO::FIFO(const Params *p)
+    : BaseSetAssoc(p)
+{
+}
+
+CacheBlk*
+FIFO::accessBlock(Addr addr, bool is_secure, Cycles &lat, int master_id)
+{
+    CacheBlk *blk = BaseSetAssoc::accessBlock(addr, is_secure, lat, master_id);
+
+    return blk;
+}
+
+CacheBlk*
+FIFO::findVictim(Addr addr)
+{
+    int set = extractSet(addr);
+    // grab a replacement candidate
+    BlkType *blk = nullptr;
+    for (int i = assoc-1; i >= 0; i--) {
+        BlkType *b = sets[set].blks[i];
+        if (b->way < allocAssoc) {
+            blk = b;
+            break;
+        }
+    }
+    assert(!blk || blk->way < allocAssoc);
+
+    if (blk && blk->isValid()) {
+        DPRINTF(CacheRepl, "set %x: selecting blk %x for replacement\n",
+                set, regenerateBlkAddr(blk->tag, set));
+    }
+
+    return blk;
+}
+
+void
+FIFO::insertBlock(PacketPtr pkt, BlkType *blk)
+{
+    BaseSetAssoc::insertBlock(pkt, blk);
+
+    int set = extractSet(pkt->getAddr());
+    sets[set].moveToHead(blk);
+}
+
+void
+FIFO::invalidate(CacheBlk *blk)
+{
+    BaseSetAssoc::invalidate(blk);
+
+    // should be evicted before valid blocks
+    int set = blk->set;
+    sets[set].moveToTail(blk);
+}
+
+FIFO*
+FIFOParams::create()
+{
+    return new FIFO(this);
+}

src/mem/cache/tags/fifo.hh

@@ -0,0 +1,41 @@
+/*
+ * Authors: Ranjeet Kumar
+ */
+
+/**
+ * @file
+ * Declaration of a FIFO tag store.
+ * The FIFO tags guarantee that the true least-recently-used way in
+ * a set will always be evicted.
+ */
+
+#ifndef __MEM_CACHE_TAGS_FIFO_HH__
+#define __MEM_CACHE_TAGS_FIFO_HH__
+
+#include "mem/cache/tags/base_set_assoc.hh"
+#include "params/FIFO.hh"
+
+class FIFO : public BaseSetAssoc
+{
+  public:
+    /** Convenience typedef. */
+    typedef FIFOParams Params;
+
+    /**
+     * Construct and initialize this tag store.
+     */
+    FIFO(const Params *p);
+
+    /**
+     * Destructor
+     */
+    ~FIFO() {}
+
+    CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat,
+                         int context_src);
+    CacheBlk* findVictim(Addr addr);
+    void insertBlock(PacketPtr pkt, BlkType *blk);
+    void invalidate(CacheBlk *blk);
+};
+
+#endif // __MEM_CACHE_TAGS_FIFO_HH__