base: Add error messages to BloomFilter::Perfect

Warn the user when they use BloomFilter::Perfect's
parameters incorrectly.

Change-Id: Ib493c5f508e47a5f18e43c023755ef960954f5cc
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/44112
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/filters/BloomFilters.py

@@ -98,3 +98,8 @@ class BloomFilterPerfect(BloomFilterBase):
 
     # The base filter is not needed. Use a dummy value.
     size = 1
+
+    # This filter does not use saturating counters - as long as the entry is
+    # set, it is present; thus, it only needs one bit.
+    num_bits = 1
+    threshold = 1

src/base/filters/perfect_bloom_filter.cc

@@ -28,6 +28,7 @@
 
 #include "base/filters/perfect_bloom_filter.hh"
 
+#include "base/logging.hh"
 #include "params/BloomFilterPerfect.hh"
 
 namespace gem5
@@ -40,6 +41,12 @@ namespace bloom_filter
 Perfect::Perfect(const BloomFilterPerfectParams &p)
     : Base(p)
 {
+    fatal_if(p.size != 1, "The perfect Bloom filter cannot be limited to a "
+        "specific size.");
+    fatal_if(p.num_bits != 1, "The perfect Bloom filter tracks entries "
+        "perfectly using an unlimited amount of 1-bit entries.");
+    fatal_if(p.threshold != 1, "The perfect Bloom filter uses 1-bit entries; "
+        "thus, their thresholds must be 1.");
 }
 
 Perfect::~Perfect()