arch: Resurrect the NOISA build target and rename it NULL

This patch makes it possible to once again build gem5 without any
ISA. The main purpose is to enable work around the interconnect and
memory system without having to build any CPU models or device models.

The regress script is updated to include the NULL ISA target. Currently
no regressions make use of it, but all the testers could (and perhaps
should) transition to it.

--HG--
rename : build_opts/NOISA => build_opts/NULL
rename : src/arch/noisa/SConsopts => src/arch/null/SConsopts
rename : src/arch/noisa/cpu_dummy.hh => src/arch/null/cpu_dummy.hh
rename : src/cpu/intr_control.cc => src/cpu/intr_control_noisa.cc

39 files changed, 575 insertions, 62 deletions

diff --git a/build_opts/NOISA b/build_opts/NOISA
deleted file mode 100644
index dd1f82a78..000000000
--- a/build_opts/NOISA
+++ /dev/null
@@ -1,2 +0,0 @@
-TARGET_ISA = 'no'
-CPU_MODELS = 'no'
diff --git a/build_opts/NULL b/build_opts/NULL
new file mode 100644
index 000000000..5d85833f3
--- /dev/null
+++ b/build_opts/NULL
@@ -0,0 +1,2 @@
+TARGET_ISA = 'null'
+CPU_MODELS = ''
diff --git a/src/arch/generic/SConscript b/src/arch/generic/SConscript
index f2edc805d..3dfc509a4 100644
--- a/src/arch/generic/SConscript
+++ b/src/arch/generic/SConscript
@@ -28,4 +28,7 @@
 
 Import('*')
 
+if env['TARGET_ISA'] == 'null':
+    Return()
+
 Source('decode_cache.cc')
diff --git a/src/arch/noisa/SConsopts b/src/arch/noisa/SConsopts
deleted file mode 100644
index fbfcf05c9..000000000
--- a/src/arch/noisa/SConsopts
+++ /dev/null
@@ -1,4 +0,0 @@
-
-Import('*')
-
-all_isa_list.append('no')
diff --git a/src/arch/noisa/cpu_dummy.hh b/src/arch/noisa/cpu_dummy.hh
deleted file mode 100644
index 0d494d6a5..000000000
--- a/src/arch/noisa/cpu_dummy.hh
+++ /dev/null
@@ -1,7 +0,0 @@
-
-class BaseCPU
-{
-  public:
-    static int numSimulatedInsts() { return 0; }
-    static int numSimulatedOps() { return 0; }
-};
diff --git a/src/arch/null/SConscript b/src/arch/null/SConscript
new file mode 100644
index 000000000..e64b69c41
--- /dev/null
+++ b/src/arch/null/SConscript
@@ -0,0 +1,43 @@
+# -*- 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.
+#
+# Authors: Andreas Hansson
+
+Import('*')
+
+if env['TARGET_ISA'] == 'null':
+    Source('cpu_dummy.cc')
diff --git a/src/arch/null/SConsopts b/src/arch/null/SConsopts
new file mode 100644
index 000000000..e377564de
--- /dev/null
+++ b/src/arch/null/SConsopts
@@ -0,0 +1,42 @@
+# -*- 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.
+#
+# Authors: Andreas Hansson
+
+Import('*')
+
+all_isa_list.append('null')
diff --git a/src/arch/null/cpu_dummy.cc b/src/arch/null/cpu_dummy.cc
new file mode 100644
index 000000000..4c78bf777
--- /dev/null
+++ b/src/arch/null/cpu_dummy.cc
@@ -0,0 +1,44 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+/**
+ * Provide the actual storage for maxThreadsPerCPU which is declared
+ * extern and normally provided by src/cpu/base.cc
+ */
+int maxThreadsPerCPU = 1;
diff --git a/src/arch/null/cpu_dummy.hh b/src/arch/null/cpu_dummy.hh
new file mode 100644
index 000000000..ed6f6d1d6
--- /dev/null
+++ b/src/arch/null/cpu_dummy.hh
@@ -0,0 +1,52 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+#ifndef __ARCH_NULL_CPU_DUMMY_HH__
+#define __ARCH_NULL_CPU_DUMMY_HH__
+
+#include "sim/core.hh"
+
+class BaseCPU
+{
+  public:
+    static int numSimulatedInsts() { return 0; }
+    static int numSimulatedOps() { return 0; }
+};
+
+#endif // __ARCH_NULL_CPU_DUMMY_HH__
diff --git a/src/arch/null/isa_traits.hh b/src/arch/null/isa_traits.hh
new file mode 100644
index 000000000..d09b1e876
--- /dev/null
+++ b/src/arch/null/isa_traits.hh
@@ -0,0 +1,59 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+#ifndef __ARCH_NULL_ISA_TRAITS_HH__
+#define __ARCH_NULL_ISA_TRAITS_HH__
+
+#include "base/types.hh"
+
+namespace LittleEndianGuest {}
+
+namespace NullISA
+{
+    using namespace LittleEndianGuest;
+
+    const Addr PageShift = 12;
+    const Addr PageBytes = ULL(1) << PageShift;
+
+    const int LogVMPageSize = 12;       // 4K bytes
+    const int VMPageSize = (1 << LogVMPageSize);
+
+}
+
+#endif //__ARCH_NULL_ISA_TRAITS_HH__
diff --git a/src/arch/null/registers.hh b/src/arch/null/registers.hh
new file mode 100644
index 000000000..f33b7e5bd
--- /dev/null
+++ b/src/arch/null/registers.hh
@@ -0,0 +1,54 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+#ifndef __ARCH_NULL_REGISTERS_HH__
+#define __ARCH_NULL_REGISTERS_HH__
+
+#include "base/types.hh"
+
+namespace NullISA {
+
+typedef uint64_t IntReg;
+typedef uint32_t FloatRegBits;
+typedef float FloatReg;
+typedef uint64_t MiscReg;
+
+}
+
+#endif // __ARCH_NULL_REGISTERS_HH__
diff --git a/src/arch/null/remote_gdb.hh b/src/arch/null/remote_gdb.hh
new file mode 100644
index 000000000..dddebce7d
--- /dev/null
+++ b/src/arch/null/remote_gdb.hh
@@ -0,0 +1,56 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+#ifndef __ARCH_NULL_REMOTE_GDB_HH__
+#define __ARCH_NULL_REMOTE_GDB_HH__
+
+class ThreadContext;
+
+class BaseRemoteGDB
+{
+
+  public:
+
+    bool breakpoint() { return false; }
+    void replaceThreadContext(ThreadContext *tc) {}
+
+    virtual ~BaseRemoteGDB() {}
+};
+
+#endif // __ARCH_NULL_REMOTE_GDB_H__
diff --git a/src/arch/null/types.hh b/src/arch/null/types.hh
new file mode 100644
index 000000000..b62b8f2ff
--- /dev/null
+++ b/src/arch/null/types.hh
@@ -0,0 +1,58 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+#ifndef __ARCH_NULL_TYPES_HH__
+#define __ARCH_NULL_TYPES_HH__
+
+#include "arch/generic/types.hh"
+
+namespace NullISA
+{
+    typedef uint32_t MachInst;
+
+    class PCState : public GenericISA::UPCState<MachInst>
+    {
+      protected:
+
+        typedef GenericISA::UPCState<MachInst> Base;
+    };
+
+}
+
+#endif // __ARCH_NULL_TYPES_HH__
diff --git a/src/arch/null/utility.hh b/src/arch/null/utility.hh
new file mode 100644
index 000000000..cf65ef5cd
--- /dev/null
+++ b/src/arch/null/utility.hh
@@ -0,0 +1,55 @@
+/*
+ * 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.
+ *
+ * Authors: Andreas Hansson
+ */
+
+#ifndef __ARCH_NULL_UTILITY_HH__
+#define __ARCH_NULL_UTILITY_HH__
+
+#include "base/types.hh"
+#include "cpu/thread_context.hh"
+
+namespace NullISA {
+
+inline uint64_t getArgument(ThreadContext *tc, int &number, uint16_t size,
+                            bool fp) { return 0; }
+
+inline void startupCPU(ThreadContext *tc, int cpuId) {}
+
+}
+
+#endif // __ARCH_NULL_UTILITY_HH__
diff --git a/src/base/SConscript b/src/base/SConscript
index b2a348f15..8c32bb3c9 100644
--- a/src/base/SConscript
+++ b/src/base/SConscript
@@ -52,7 +52,7 @@ Source('output.cc')
 Source('pollevent.cc')
 Source('random.cc')
 Source('random_mt.cc')
-if env['TARGET_ISA'] != 'no':
+if env['TARGET_ISA'] != 'null':
     Source('remote_gdb.cc')
 Source('socket.cc')
 Source('statistics.cc')
diff --git a/src/cpu/SConscript b/src/cpu/SConscript
index c52dbc53b..999de1e49 100644
--- a/src/cpu/SConscript
+++ b/src/cpu/SConscript
@@ -30,7 +30,9 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
+if env['TARGET_ISA'] == 'null':
+    SimObject('IntrControl.py')
+    Source('intr_control_noisa.cc')
     Return()
 
 #################################################################
diff --git a/src/cpu/base.hh b/src/cpu/base.hh
index 9e7198763..540c72833 100644
--- a/src/cpu/base.hh
+++ b/src/cpu/base.hh
@@ -48,11 +48,16 @@
 
 #include <vector>
 
+// Before we do anything else, check if this build is the NULL ISA,
+// and if so stop here
+#include "config/the_isa.hh"
+#if THE_ISA == NULL_ISA
+#include "arch/null/cpu_dummy.hh"
+#else
 #include "arch/interrupts.hh"
 #include "arch/isa_traits.hh"
 #include "arch/microcode_rom.hh"
 #include "base/statistics.hh"
-#include "config/the_isa.hh"
 #include "mem/mem_object.hh"
 #include "sim/eventq.hh"
 #include "sim/full_system.hh"
@@ -476,4 +481,6 @@ class BaseCPU : public MemObject
     Stats::Scalar numWorkItemsCompleted;
 };
 
+#endif // THE_ISA == NULL_ISA
+
 #endif // __CPU_BASE_HH__
diff --git a/src/cpu/intr_control_noisa.cc b/src/cpu/intr_control_noisa.cc
new file mode 100644
index 000000000..ff49976d0
--- /dev/null
+++ b/src/cpu/intr_control_noisa.cc
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2002-2005 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * Authors: Nathan Binkert
+ *          Ron Dreslinski
+ */
+
+#include "cpu/intr_control.hh"
+
+using namespace std;
+
+IntrControl::IntrControl(const Params *p)
+    : SimObject(p), sys(p->sys)
+{}
+
+void
+IntrControl::post(int cpu_id, int int_num, int index)
+{
+}
+
+void
+IntrControl::clear(int cpu_id, int int_num, int index)
+{
+}
+
+IntrControl *
+IntrControlParams::create()
+{
+    return new IntrControl(this);
+}
diff --git a/src/dev/SConscript b/src/dev/SConscript
index cba821f87..1bcddb6ee 100644
--- a/src/dev/SConscript
+++ b/src/dev/SConscript
@@ -31,7 +31,7 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
+if env['TARGET_ISA'] == 'null':
     Return()
 
 SimObject('BadDevice.py')
diff --git a/src/dev/sinic.cc b/src/dev/sinic.cc
index 02eb8a113..7da70c482 100644
--- a/src/dev/sinic.cc
+++ b/src/dev/sinic.cc
@@ -32,7 +32,9 @@
 #include <limits>
 #include <string>
 
+#ifdef SINIC_VTOPHYS
 #include "arch/vtophys.hh"
+#endif
 #include "base/compiler.hh"
 #include "base/debug.hh"
 #include "base/inet.hh"
diff --git a/src/kern/SConscript b/src/kern/SConscript
index 38734e650..2f4d70a48 100644
--- a/src/kern/SConscript
+++ b/src/kern/SConscript
@@ -30,7 +30,7 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
+if env['TARGET_ISA'] == 'null':
     Return()
 
 Source('kernel_stats.cc')
diff --git a/src/mem/SConscript b/src/mem/SConscript
index ca89418b5..02d0aee73 100644
--- a/src/mem/SConscript
+++ b/src/mem/SConscript
@@ -36,11 +36,15 @@ if env['HAVE_PROTOBUF']:
     SimObject('CommMonitor.py')
     Source('comm_monitor.cc')
 
+SimObject('AbstractMemory.py')
 SimObject('AddrMapper.py')
 SimObject('Bridge.py')
 SimObject('Bus.py')
 SimObject('MemObject.py')
+SimObject('SimpleMemory.py')
+SimObject('SimpleDRAM.py')
 
+Source('abstract_mem.cc')
 Source('addr_mapper.cc')
 Source('bridge.cc')
 Source('bus.cc')
@@ -53,18 +57,14 @@ Source('port.cc')
 Source('packet_queue.cc')
 Source('tport.cc')
 Source('port_proxy.cc')
-Source('fs_translating_port_proxy.cc')
-Source('se_translating_port_proxy.cc')
+Source('simple_mem.cc')
+Source('physical.cc')
+Source('simple_dram.cc')
 
-if env['TARGET_ISA'] != 'no':
-    SimObject('AbstractMemory.py')
-    SimObject('SimpleMemory.py')
-    SimObject('SimpleDRAM.py')
-    Source('abstract_mem.cc')
-    Source('simple_mem.cc')
+if env['TARGET_ISA'] != 'null':
+    Source('fs_translating_port_proxy.cc')
+    Source('se_translating_port_proxy.cc')
     Source('page_table.cc')
-    Source('physical.cc')
-    Source('simple_dram.cc')
 
 DebugFlag('BaseBus')
 DebugFlag('BusAddrRanges')
diff --git a/src/mem/cache/SConscript b/src/mem/cache/SConscript
index 8323602d2..a4fbe04c0 100644
--- a/src/mem/cache/SConscript
+++ b/src/mem/cache/SConscript
@@ -30,9 +30,6 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
-    Return()
-
 SimObject('BaseCache.py')
 
 Source('base.cc')
diff --git a/src/mem/cache/base.cc b/src/mem/cache/base.cc
index 03b4d5dc1..af324527f 100644
--- a/src/mem/cache/base.cc
+++ b/src/mem/cache/base.cc
@@ -45,8 +45,6 @@
  * Definition of BaseCache functions.
  */
 
-#include "cpu/base.hh"
-#include "cpu/smt.hh"
 #include "debug/Cache.hh"
 #include "debug/Drain.hh"
 #include "mem/cache/tags/fa_lru.hh"
diff --git a/src/mem/cache/prefetch/SConscript b/src/mem/cache/prefetch/SConscript
index 2310940c1..61291f715 100644
--- a/src/mem/cache/prefetch/SConscript
+++ b/src/mem/cache/prefetch/SConscript
@@ -30,8 +30,6 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
-    Return()
 SimObject('Prefetcher.py')
 
 Source('base.cc')
diff --git a/src/mem/cache/tags/SConscript b/src/mem/cache/tags/SConscript
index de835c1d0..dca8d3bd8 100644
--- a/src/mem/cache/tags/SConscript
+++ b/src/mem/cache/tags/SConscript
@@ -30,9 +30,6 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
-    Return()
-
 SimObject('Tags.py')
 
 Source('base.cc')
diff --git a/src/mem/cache/tags/base.cc b/src/mem/cache/tags/base.cc
index d9909f5de..947bd05de 100644
--- a/src/mem/cache/tags/base.cc
+++ b/src/mem/cache/tags/base.cc
@@ -46,6 +46,7 @@
  * Definitions of BaseTags.
  */
 
+#include "config/the_isa.hh"
 #include "cpu/smt.hh" //maxThreadsPerCPU
 #include "mem/cache/tags/base.hh"
 #include "mem/cache/base.hh"
diff --git a/src/mem/fs_translating_port_proxy.cc b/src/mem/fs_translating_port_proxy.cc
index 8fb9b91ef..52e8b49d8 100644
--- a/src/mem/fs_translating_port_proxy.cc
+++ b/src/mem/fs_translating_port_proxy.cc
@@ -46,6 +46,7 @@
  * Port object definitions.
  */
 
+#include "arch/vtophys.hh"
 #include "base/chunk_generator.hh"
 #include "cpu/base.hh"
 #include "cpu/thread_context.hh"
diff --git a/src/mem/fs_translating_port_proxy.hh b/src/mem/fs_translating_port_proxy.hh
index 2a9223050..c8f099d2c 100644
--- a/src/mem/fs_translating_port_proxy.hh
+++ b/src/mem/fs_translating_port_proxy.hh
@@ -59,9 +59,10 @@
 #ifndef __MEM_FS_PORT_PROXY_HH__
 #define __MEM_FS_PORT_PROXY_HH__
 
-#include "arch/vtophys.hh"
 #include "mem/port_proxy.hh"
 
+class ThreadContext;
+
 /**
  * A TranslatingPortProxy in FS mode translates a virtual address to a
  * physical address and then calls the read/write functions of the
diff --git a/src/mem/port_proxy.hh b/src/mem/port_proxy.hh
index f1e01c385..1213daafa 100644
--- a/src/mem/port_proxy.hh
+++ b/src/mem/port_proxy.hh
@@ -60,7 +60,7 @@
 #define __MEM_PORT_PROXY_HH__
 
 #include "config/the_isa.hh"
-#if THE_ISA != NO_ISA
+#if THE_ISA != NULL_ISA
     #include "arch/isa_traits.hh"
 #endif
 
@@ -127,7 +127,7 @@ class PortProxy
     template <typename T>
     void write(Addr address, T data) const;
 
-#if THE_ISA != NO_ISA
+#if THE_ISA != NULL_ISA
     /**
      * Read sizeof(T) bytes from address and return as object T.
      * Performs Guest to Host endianness transform.
@@ -161,7 +161,7 @@ PortProxy::write(Addr address, T data) const
     writeBlob(address, (uint8_t*)&data, sizeof(T));
 }
 
-#if THE_ISA != NO_ISA
+#if THE_ISA != NULL_ISA
 template <typename T>
 T
 PortProxy::readGtoH(Addr address) const
diff --git a/src/mem/ruby/SConscript b/src/mem/ruby/SConscript
index 086c2f764..b655caa7d 100644
--- a/src/mem/ruby/SConscript
+++ b/src/mem/ruby/SConscript
@@ -37,7 +37,7 @@ import SCons
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
+if env['TARGET_ISA'] == 'null':
     Return()
 
 if env['PROTOCOL'] == 'None':
diff --git a/src/python/swig/pyobject.cc b/src/python/swig/pyobject.cc
index f534623f8..fe849ec88 100644
--- a/src/python/swig/pyobject.cc
+++ b/src/python/swig/pyobject.cc
@@ -34,16 +34,19 @@
 
 #include "base/inifile.hh"
 #include "base/output.hh"
+#include "config/the_isa.hh"
+#if THE_ISA != NULL_ISA
 #include "dev/etherdevice.hh"
 #include "dev/etherobject.hh"
+#endif
 #include "mem/mem_object.hh"
-#include "mem/port.hh"
 #include "python/swig/pyobject.hh"
 #include "sim/full_system.hh"
 #include "sim/sim_object.hh"
 
 using namespace std;
 
+#if THE_ISA != NULL_ISA
 EtherInt *
 lookupEthPort(SimObject *so, const std::string &name, int i)
 {
@@ -61,6 +64,7 @@ lookupEthPort(SimObject *so, const std::string &name, int i)
         p = ed->getEthPort(name, i);
     return p;
 }
+#endif
 
 /**
  * Connect the described MemObject ports.  Called from Python via SWIG.
@@ -71,6 +75,7 @@ int
 connectPorts(SimObject *o1, const std::string &name1, int i1,
              SimObject *o2, const std::string &name2, int i2)
 {
+#if THE_ISA != NULL_ISA
     if (FullSystem) {
         EtherObject *eo1, *eo2;
         EtherDevice *ed1, *ed2;
@@ -92,6 +97,7 @@ connectPorts(SimObject *o1, const std::string &name1, int i1,
             }
         }
     }
+#endif
     MemObject *mo1, *mo2;
     mo1 = dynamic_cast<MemObject*>(o1);
     mo2 = dynamic_cast<MemObject*>(o2);
diff --git a/src/sim/SConscript b/src/sim/SConscript
index 90d77848b..850af230e 100644
--- a/src/sim/SConscript
+++ b/src/sim/SConscript
@@ -33,9 +33,9 @@ Import('*')
 SimObject('BaseTLB.py')
 SimObject('ClockedObject.py')
 SimObject('Root.py')
-SimObject('InstTracer.py')
 SimObject('ClockDomain.py')
 SimObject('VoltageDomain.py')
+SimObject('System.py')
 
 Source('arguments.cc')
 Source('async.cc')
@@ -51,19 +51,17 @@ Source('sim_events.cc')
 Source('sim_object.cc')
 Source('simulate.cc')
 Source('stat_control.cc')
-Source('syscall_emul.cc')
 Source('clock_domain.cc')
 Source('voltage_domain.cc')
+Source('system.cc')
 
-if env['TARGET_ISA'] != 'no':
+if env['TARGET_ISA'] != 'null':
+    SimObject('InstTracer.py')
     SimObject('Process.py')
-    SimObject('System.py')
     Source('faults.cc')
     Source('process.cc')
     Source('pseudo_inst.cc')
-    Source('system.cc')
-
-if env['TARGET_ISA'] != 'no':
+    Source('syscall_emul.cc')
     Source('tlb.cc')
 
 DebugFlag('Checkpoint')
diff --git a/src/sim/arguments.hh b/src/sim/arguments.hh
index fad955999..58a43852c 100644
--- a/src/sim/arguments.hh
+++ b/src/sim/arguments.hh
@@ -33,7 +33,6 @@
 
 #include <cassert>
 
-#include "arch/vtophys.hh"
 #include "base/refcnt.hh"
 #include "base/types.hh"
 #include "mem/fs_translating_port_proxy.hh"
diff --git a/src/sim/stat_control.cc b/src/sim/stat_control.cc
index 5429861d6..7a8d48ae2 100644
--- a/src/sim/stat_control.cc
+++ b/src/sim/stat_control.cc
@@ -52,13 +52,7 @@
 #include "base/hostinfo.hh"
 #include "base/statistics.hh"
 #include "base/time.hh"
-#include "config/the_isa.hh"
-#if THE_ISA == NO_ISA
-#include "arch/noisa/cpu_dummy.hh"
-#else
 #include "cpu/base.hh"
-#endif
-
 #include "sim/eventq_impl.hh"
 #include "sim/stat_control.hh"
 
diff --git a/src/sim/system.cc b/src/sim/system.cc
index 24f9dfbad..7de483216 100644
--- a/src/sim/system.cc
+++ b/src/sim/system.cc
@@ -48,7 +48,6 @@
 #include "arch/isa_traits.hh"
 #include "arch/remote_gdb.hh"
 #include "arch/utility.hh"
-#include "arch/vtophys.hh"
 #include "base/loader/object_file.hh"
 #include "base/loader/symtab.hh"
 #include "base/str.hh"
@@ -228,6 +227,7 @@ System::registerThreadContext(ThreadContext *tc, int assigned)
     threadContexts[id] = tc;
     _numContexts++;
 
+#if THE_ISA != NULL_ISA
     int port = getRemoteGDBPort();
     if (port) {
         RemoteGDB *rgdb = new RemoteGDB(this, tc);
@@ -243,6 +243,7 @@ System::registerThreadContext(ThreadContext *tc, int assigned)
 
         remoteGDB[id] = rgdb;
     }
+#endif
 
     activeCpus.push_back(false);
 
diff --git a/src/sim/system.hh b/src/sim/system.hh
index 5058e7b26..5b166eabf 100644
--- a/src/sim/system.hh
+++ b/src/sim/system.hh
@@ -184,7 +184,9 @@ class System : public MemObject
      */
     unsigned int cacheLineSize() const { return _cacheLineSize; }
 
+#if THE_ISA != NULL_ISA
     PCEventQueue pcEventQueue;
+#endif
 
     std::vector<ThreadContext *> threadContexts;
     int _numContexts;
@@ -380,11 +382,13 @@ class System : public MemObject
     {
         Addr addr = 0; // initialize only to avoid compiler warning
 
+#if THE_ISA != NULL_ISA
         if (symtab->findAddress(lbl, addr)) {
             T *ev = new T(&pcEventQueue, desc, fixFuncEventAddr(addr),
                           std::forward<Args>(args)...);
             return ev;
         }
+#endif
 
         return NULL;
     }
diff --git a/src/unittest/SConscript b/src/unittest/SConscript
index 841cbb8a6..4cb14a290 100644
--- a/src/unittest/SConscript
+++ b/src/unittest/SConscript
@@ -30,9 +30,6 @@
 
 Import('*')
 
-if env['TARGET_ISA'] == 'no':
-    Return()
-
 Source('unittest.cc')
 
 UnitTest('bitvectest', 'bitvectest.cc')
diff --git a/util/regress b/util/regress
index b17da8797..2ed2b6970 100755
--- a/util/regress
+++ b/util/regress
@@ -45,6 +45,7 @@ add_option('--builds',
            'ALPHA_MOESI_CMP_directory,' \
            'ALPHA_MOESI_CMP_token,' \
            'MIPS,' \
+           'NULL,' \
            'POWER,' \
            'SPARC,' \
            'X86,X86_MESI_CMP_directory,' \