mem,ext: Integrating DRAMSim3 with gem5

Adding DRAMSim3 source code to the gem5 source code, the original
code was taken from umd-memsys github at https://github.com/umd-memsys/

Change-Id: I32c982206f33b0acf2121f322d15baa064c412c4
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/31757
Reviewed-by: Ayaz Akram <yazakram@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

ext/dramsim3/README

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+Follow these steps to get DRAMSim3 as part of gem5
+
+1. Download DRAMSim3
+    1.1 Go to ext/dramsim3 (this directory)
+    1.2 Clone DRAMSim3: git clone git@github.com:umd-memsys/DRAMSim3.git DRAMsim3
+    1.3 cd DRAMSim3 && mkdir build
+    1.4 cd build
+    1.5 cmake ..
+    1.6 make
+
+2. Compile gem5
+    2.1 cd gem5
+    2.2 Business as usual
+

ext/dramsim3/SConscript

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+# -*- mode:python -*-
+
+# Copyright (c) 2013 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met: redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer;
+# redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution;
+# neither the name of the copyright holders nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+
+import os
+
+Import('main')
+
+thermal = False
+
+# See if we got a cloned DRAMSim3 repo as a subdirectory and set the
+# HAVE_DRAMSIM flag accordingly
+if not os.path.exists(Dir('.').srcnode().abspath + '/DRAMsim3'):
+    main['HAVE_DRAMSIM3'] = False
+    Return()
+
+# We have got the folder, so add the library and build the wrappers
+main['HAVE_DRAMSIM3'] = True
+
+
+dramsim_path = os.path.join(Dir('#').abspath, 'ext/dramsim3/DRAMsim3/')
+
+if thermal:
+    superlu_path = os.path.join(dramsim_path, 'ext/SuperLU_MT_3.1/lib')
+    main.Prepend(CPPPATH=Dir('.'))
+    main.Append(LIBS=['dramsim3', 'superlu_mt_OPENMP', 'm', 'f77blas',
+                      'atlas', 'gomp'],
+                LIBPATH=[dramsim_path, superlu_path])
+else:
+    main.Prepend(CPPPATH=Dir('.'))
+    # a littel hacky but can get a shared library working
+    main.Append(LIBS=['dramsim3', 'gomp'],
+                LIBPATH=[dramsim_path],  # compile-time lookup
+                RPATH=[dramsim_path],  # runtime lookup
+                CPPPATH=[dramsim_path+'/src/'])