mem-ruby: Enable set size increase

Add NUMBER_BITS_PER_SET environment variable to control
the size of the bitmask in Set.hh (default=64).
Necessary for configs which require >64 instances of a given
machine type. This can be set in the build_opts file, e.g.
by adding the following line:
NUMBER_BITS_PER_SET = <number>

Change-Id: I314a3cadca8ce975fcf4a60d9022494751688e88
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18968
Reviewed-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/ruby/common/SConscript

@@ -33,6 +33,8 @@ Import('*')
 if env['PROTOCOL'] == 'None':
     Return()
 
+env.Append(CPPDEFINES={'NUMBER_BITS_PER_SET': env['NUMBER_BITS_PER_SET']})
+
 Source('Address.cc')
 Source('BoolVec.cc')
 Source('Consumer.cc')

src/mem/ruby/common/Set.hh

@@ -39,13 +39,11 @@
 #include "base/logging.hh"
 #include "mem/ruby/common/TypeDefines.hh"
 
-// Change for systems with more than 64 controllers of a particular type.
-const int NUMBER_BITS_PER_SET = 64;
-
 class Set
 {
   private:
     // Number of bits in use in this set.
+    // can be defined in build_opts file (default=64).
     int m_nSize;
     std::bitset<NUMBER_BITS_PER_SET> bits;