mem-cache: Use SatCounter for prefetchers

Many prefetchers re-implement saturating counters with ints. Make
them use SatCounters instead.

Added missing operators and constructors to SatCounter for that to
be possible and their respective tests.

Change-Id: I36f10c89c27c9b3d1bf461e9ea546920f6ebb888
Signed-off-by: Daniel <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17995
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Javier Bueno Hedo <javier.bueno@metempsy.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

1 files changed, 10 insertions, 15 deletions

diff --git a/src/mem/cache/prefetch/signature_path.hh b/src/mem/cache/prefetch/signature_path.hh
index 974c02746..3bf4dd293 100644
--- a/src/mem/cache/prefetch/signature_path.hh
+++ b/src/mem/cache/prefetch/signature_path.hh
@@ -42,6 +42,7 @@
 #ifndef __MEM_CACHE_PREFETCH_SIGNATURE_PATH_HH__
 #define __MEM_CACHE_PREFETCH_SIGNATURE_PATH_HH__
 
+#include "base/sat_counter.hh"
 #include "mem/cache/prefetch/associative_set.hh"
 #include "mem/cache/prefetch/queued.hh"
 #include "mem/packet.hh"
@@ -62,8 +63,6 @@ class SignaturePathPrefetcher : public QueuedPrefetcher
     const uint8_t signatureShift;
     /** Size of the signature, in bits */
     const signature_t signatureBits;
-    /** Maximum pattern entries counter value */
-    const uint8_t maxCounterValue;
     /** Minimum confidence to issue a prefetch */
     const double prefetchConfidenceThreshold;
     /** Minimum confidence to keep navigating lookahead entries */
@@ -87,9 +86,9 @@ class SignaturePathPrefetcher : public QueuedPrefetcher
     {
         /** stride in a page in blkSize increments */
         stride_t stride;
-        /** counter value (max value defined by maxCounterValue) */
-        uint8_t counter;
-        PatternStrideEntry() : stride(0), counter(0)
+        /** Saturating counter */
+        SatCounter counter;
+        PatternStrideEntry(unsigned bits) : stride(0), counter(bits)
         {}
     };
     /** Pattern entry data type, a set of stride and counter entries */
@@ -98,19 +97,19 @@ class SignaturePathPrefetcher : public QueuedPrefetcher
         /** group of stides */
         std::vector<PatternStrideEntry> strideEntries;
         /** use counter, used by SPPv2 */
-        uint8_t counter;
-        PatternEntry(size_t num_strides) : strideEntries(num_strides),
-                                           counter(0)
+        SatCounter counter;
+        PatternEntry(size_t num_strides, unsigned counter_bits)
+            : strideEntries(num_strides, counter_bits), counter(counter_bits)
         {}
 
         /** Reset the entries to their initial values */
         void reset() override
         {
             for (auto &entry : strideEntries) {
-                entry.counter = 0;
+                entry.counter.reset();
                 entry.stride = 0;
             }
-            counter = 0;
+            counter.reset();
         }
 
         /**
@@ -135,13 +134,9 @@ class SignaturePathPrefetcher : public QueuedPrefetcher
          * Gets the entry with the provided stride, if there is no entry with
          * the associated stride, it replaces one of them.
          * @param stride the stride to find
-         * @param max_counter_value maximum value of the confidence counters,
-         *        it is used when no strides are found and an entry needs to be
-         *        replaced
          * @result reference to the selected entry
          */
-        PatternStrideEntry &getStrideEntry(stride_t stride,
-                                           uint8_t max_counter_value);
+        PatternStrideEntry &getStrideEntry(stride_t stride);
     };
     /** Pattern table */
     AssociativeSet<PatternEntry> patternTable;