arch: Make the ISA class inherit from SimObject

The ISA class on stores the contents of ID registers on many
architectures. In order to make reset values of such registers
configurable, we make the class inherit from SimObject, which allows
us to use the normal generated parameter headers.

This patch introduces a Python helper method, BaseCPU.createThreads(),
which creates a set of ISAs for each of the threads in an SMT
system. Although it is currently only needed when creating
multi-threaded CPUs, it should always be called before instantiating
the system as this is an obvious place to configure ID registers
identifying a thread/CPU.

18 files changed, 104 insertions, 59 deletions

diff --git a/src/cpu/BaseCPU.py b/src/cpu/BaseCPU.py
index dfbd459fd..697be87e1 100644
--- a/src/cpu/BaseCPU.py
+++ b/src/cpu/BaseCPU.py
@@ -57,21 +57,33 @@ default_tracer = ExeTracer()
 if buildEnv['TARGET_ISA'] == 'alpha':
     from AlphaTLB import AlphaDTB, AlphaITB
     from AlphaInterrupts import AlphaInterrupts
+    from AlphaISA import AlphaISA
+    isa_class = AlphaISA
 elif buildEnv['TARGET_ISA'] == 'sparc':
     from SparcTLB import SparcTLB
     from SparcInterrupts import SparcInterrupts
+    from SparcISA import SparcISA
+    isa_class = SparcISA
 elif buildEnv['TARGET_ISA'] == 'x86':
     from X86TLB import X86TLB
     from X86LocalApic import X86LocalApic
+    from X86ISA import X86ISA
+    isa_class = X86ISA
 elif buildEnv['TARGET_ISA'] == 'mips':
     from MipsTLB import MipsTLB
     from MipsInterrupts import MipsInterrupts
+    from MipsISA import MipsISA
+    isa_class = MipsISA
 elif buildEnv['TARGET_ISA'] == 'arm':
     from ArmTLB import ArmTLB
     from ArmInterrupts import ArmInterrupts
+    from ArmISA import ArmISA
+    isa_class = ArmISA
 elif buildEnv['TARGET_ISA'] == 'power':
     from PowerTLB import PowerTLB
     from PowerInterrupts import PowerInterrupts
+    from PowerISA import PowerISA
+    isa_class = PowerISA
 
 class BaseCPU(MemObject):
     type = 'BaseCPU'
@@ -113,31 +125,37 @@ class BaseCPU(MemObject):
         itb = Param.SparcTLB(SparcTLB(), "Instruction TLB")
         interrupts = Param.SparcInterrupts(
                 NULL, "Interrupt Controller")
+        isa = VectorParam.SparcISA([ isa_class() ], "ISA instance")
     elif buildEnv['TARGET_ISA'] == 'alpha':
         dtb = Param.AlphaTLB(AlphaDTB(), "Data TLB")
         itb = Param.AlphaTLB(AlphaITB(), "Instruction TLB")
         interrupts = Param.AlphaInterrupts(
                 NULL, "Interrupt Controller")
+        isa = VectorParam.AlphaISA([ isa_class() ], "ISA instance")
     elif buildEnv['TARGET_ISA'] == 'x86':
         dtb = Param.X86TLB(X86TLB(), "Data TLB")
         itb = Param.X86TLB(X86TLB(), "Instruction TLB")
         interrupts = Param.X86LocalApic(NULL, "Interrupt Controller")
+        isa = VectorParam.X86ISA([ isa_class() ], "ISA instance")
     elif buildEnv['TARGET_ISA'] == 'mips':
         dtb = Param.MipsTLB(MipsTLB(), "Data TLB")
         itb = Param.MipsTLB(MipsTLB(), "Instruction TLB")
         interrupts = Param.MipsInterrupts(
                 NULL, "Interrupt Controller")
+        isa = VectorParam.MipsISA([ isa_class() ], "ISA instance")
     elif buildEnv['TARGET_ISA'] == 'arm':
         dtb = Param.ArmTLB(ArmTLB(), "Data TLB")
         itb = Param.ArmTLB(ArmTLB(), "Instruction TLB")
         interrupts = Param.ArmInterrupts(
                 NULL, "Interrupt Controller")
+        isa = VectorParam.ArmISA([ isa_class() ], "ISA instance")
     elif buildEnv['TARGET_ISA'] == 'power':
         UnifiedTLB = Param.Bool(True, "Is this a Unified TLB?")
         dtb = Param.PowerTLB(PowerTLB(), "Data TLB")
         itb = Param.PowerTLB(PowerTLB(), "Instruction TLB")
         interrupts = Param.PowerInterrupts(
                 NULL, "Interrupt Controller")
+        isa = VectorParam.PowerISA([ isa_class() ], "ISA instance")
     else:
         print "Don't know what TLB to use for ISA %s" % \
             buildEnv['TARGET_ISA']
@@ -241,5 +259,10 @@ class BaseCPU(MemObject):
         self.toL2Bus.master = self.l2cache.cpu_side
         self._cached_ports = ['l2cache.mem_side']
 
+    def createThreads(self):
+        self.isa = [ isa_class() for i in xrange(self.numThreads) ]
+        if self.checker != NULL:
+            self.checker.createThreads()
+
     def addCheckerCpu(self):
         pass
diff --git a/src/cpu/base.cc b/src/cpu/base.cc
index aaf9c9cbc..2b1df6696 100644
--- a/src/cpu/base.cc
+++ b/src/cpu/base.cc
@@ -230,6 +230,11 @@ BaseCPU::BaseCPU(Params *p, bool is_checker)
             profileEvent = new ProfileEvent(this, params()->profile);
     }
     tracer = params()->tracer;
+
+    if (params()->isa.size() != numThreads) {
+        fatal("Number of ISAs (%i) assigned to the CPU does not equal number "
+              "of threads (%i).\n", params()->isa.size(), numThreads);
+    }
 }
 
 void
diff --git a/src/cpu/checker/cpu.cc b/src/cpu/checker/cpu.cc
index 3c1690ac3..f695c24df 100644
--- a/src/cpu/checker/cpu.cc
+++ b/src/cpu/checker/cpu.cc
@@ -96,14 +96,17 @@ CheckerCPU::~CheckerCPU()
 void
 CheckerCPU::setSystem(System *system)
 {
+    const Params *p(dynamic_cast<const Params *>(_params));
+
     systemPtr = system;
 
     if (FullSystem) {
-        thread = new SimpleThread(this, 0, systemPtr, itb, dtb, false);
+        thread = new SimpleThread(this, 0, systemPtr, itb, dtb,
+                                  p->isa[0], false);
     } else {
         thread = new SimpleThread(this, 0, systemPtr,
                                   workload.size() ? workload[0] : NULL,
-                                  itb, dtb);
+                                  itb, dtb, p->isa[0]);
     }
 
     tc = thread->getTC();
diff --git a/src/cpu/dummy_checker.cc b/src/cpu/dummy_checker.cc
index 6a0210e3b..7a5b46e43 100644
--- a/src/cpu/dummy_checker.cc
+++ b/src/cpu/dummy_checker.cc
@@ -69,6 +69,7 @@ DummyCheckerParams::create()
 
     params->itb = itb;
     params->dtb = dtb;
+    params->isa = isa;
     params->system = system;
     params->cpu_id = cpu_id;
     params->profile = profile;
diff --git a/src/cpu/inorder/cpu.cc b/src/cpu/inorder/cpu.cc
index 5815775f9..1ca0657ad 100644
--- a/src/cpu/inorder/cpu.cc
+++ b/src/cpu/inorder/cpu.cc
@@ -230,6 +230,7 @@ InOrderCPU::InOrderCPU(Params *params)
       tickEvent(this),
       stageWidth(params->stageWidth),
       resPool(new ResourcePool(this, params)),
+      isa(numThreads, NULL),
       timeBuffer(2 , 2),
       dataPort(resPool->getDataUnit(), ".dcache_port"),
       instPort(resPool->getInstUnit(), ".icache_port"),
@@ -280,6 +281,7 @@ InOrderCPU::InOrderCPU(Params *params)
     }
 
     for (ThreadID tid = 0; tid < numThreads; ++tid) {
+        isa[tid] = params->isa[tid];
         pc[tid].set(0);
         lastCommittedPC[tid].set(0);
 
@@ -358,7 +360,7 @@ InOrderCPU::InOrderCPU(Params *params)
 
         memset(intRegs[tid], 0, sizeof(intRegs[tid]));
         memset(floatRegs.i[tid], 0, sizeof(floatRegs.i[tid]));
-        isa[tid].clear();
+        isa[tid]->clear();
 
         // Define dummy instructions and resource requests to be used.
         dummyInst[tid] = new InOrderDynInst(this, 
@@ -1249,11 +1251,11 @@ InOrderCPU::flattenRegIdx(RegIndex reg_idx, RegType &reg_type, ThreadID tid)
 {
     if (reg_idx < FP_Base_DepTag) {
         reg_type = IntType;
-        return isa[tid].flattenIntIndex(reg_idx);
+        return isa[tid]->flattenIntIndex(reg_idx);
     } else if (reg_idx < Ctrl_Base_DepTag) {
         reg_type = FloatType;
         reg_idx -= FP_Base_DepTag;
-        return isa[tid].flattenFloatIndex(reg_idx);
+        return isa[tid]->flattenFloatIndex(reg_idx);
     } else {
         reg_type = MiscType;
         return reg_idx - TheISA::Ctrl_Base_DepTag;
@@ -1369,25 +1371,25 @@ InOrderCPU::setRegOtherThread(unsigned reg_idx, const MiscReg &val,
 MiscReg
 InOrderCPU::readMiscRegNoEffect(int misc_reg, ThreadID tid)
 {
-    return isa[tid].readMiscRegNoEffect(misc_reg);
+    return isa[tid]->readMiscRegNoEffect(misc_reg);
 }
 
 MiscReg
 InOrderCPU::readMiscReg(int misc_reg, ThreadID tid)
 {
-    return isa[tid].readMiscReg(misc_reg, tcBase(tid));
+    return isa[tid]->readMiscReg(misc_reg, tcBase(tid));
 }
 
 void
 InOrderCPU::setMiscRegNoEffect(int misc_reg, const MiscReg &val, ThreadID tid)
 {
-    isa[tid].setMiscRegNoEffect(misc_reg, val);
+    isa[tid]->setMiscRegNoEffect(misc_reg, val);
 }
 
 void
 InOrderCPU::setMiscReg(int misc_reg, const MiscReg &val, ThreadID tid)
 {
-    isa[tid].setMiscReg(misc_reg, val, tcBase(tid));
+    isa[tid]->setMiscReg(misc_reg, val, tcBase(tid));
 }
 
 
diff --git a/src/cpu/inorder/cpu.hh b/src/cpu/inorder/cpu.hh
index a0fe834e8..acdac11d9 100644
--- a/src/cpu/inorder/cpu.hh
+++ b/src/cpu/inorder/cpu.hh
@@ -325,7 +325,7 @@ class InOrderCPU : public BaseCPU
     TheISA::IntReg intRegs[ThePipeline::MaxThreads][TheISA::NumIntRegs];
 
     /** ISA state */
-    TheISA::ISA isa[ThePipeline::MaxThreads];
+    std::vector<TheISA::ISA *> isa;
 
     /** Dependency Tracker for Integer & Floating Point Regs */
     RegDepMap archRegDepMap[ThePipeline::MaxThreads];
diff --git a/src/cpu/inorder/thread_context.cc b/src/cpu/inorder/thread_context.cc
index b8662ef4c..6b3375a52 100644
--- a/src/cpu/inorder/thread_context.cc
+++ b/src/cpu/inorder/thread_context.cc
@@ -173,7 +173,7 @@ InOrderThreadContext::copyArchRegs(ThreadContext *src_tc)
 void
 InOrderThreadContext::clearArchRegs()
 {
-    cpu->isa[thread->threadId()].clear();
+    cpu->isa[thread->threadId()]->clear();
 }
 
 
@@ -181,7 +181,7 @@ uint64_t
 InOrderThreadContext::readIntReg(int reg_idx)
 {
     ThreadID tid = thread->threadId();
-    reg_idx = cpu->isa[tid].flattenIntIndex(reg_idx);
+    reg_idx = cpu->isa[tid]->flattenIntIndex(reg_idx);
     return cpu->readIntReg(reg_idx, tid);
 }
 
@@ -189,7 +189,7 @@ FloatReg
 InOrderThreadContext::readFloatReg(int reg_idx)
 {
     ThreadID tid = thread->threadId();
-    reg_idx = cpu->isa[tid].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[tid]->flattenFloatIndex(reg_idx);
     return cpu->readFloatReg(reg_idx, tid);
 }
 
@@ -197,7 +197,7 @@ FloatRegBits
 InOrderThreadContext::readFloatRegBits(int reg_idx)
 {
     ThreadID tid = thread->threadId();
-    reg_idx = cpu->isa[tid].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[tid]->flattenFloatIndex(reg_idx);
     return cpu->readFloatRegBits(reg_idx, tid);
 }
 
@@ -211,7 +211,7 @@ void
 InOrderThreadContext::setIntReg(int reg_idx, uint64_t val)
 {
     ThreadID tid = thread->threadId();
-    reg_idx = cpu->isa[tid].flattenIntIndex(reg_idx);
+    reg_idx = cpu->isa[tid]->flattenIntIndex(reg_idx);
     cpu->setIntReg(reg_idx, val, tid);
 }
 
@@ -219,7 +219,7 @@ void
 InOrderThreadContext::setFloatReg(int reg_idx, FloatReg val)
 {
     ThreadID tid = thread->threadId();
-    reg_idx = cpu->isa[tid].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[tid]->flattenFloatIndex(reg_idx);
     cpu->setFloatReg(reg_idx, val, tid);
 }
 
@@ -227,7 +227,7 @@ void
 InOrderThreadContext::setFloatRegBits(int reg_idx, FloatRegBits val)
 {
     ThreadID tid = thread->threadId();
-    reg_idx = cpu->isa[tid].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[tid]->flattenFloatIndex(reg_idx);
     cpu->setFloatRegBits(reg_idx, val, tid);
 }
 
diff --git a/src/cpu/inorder/thread_context.hh b/src/cpu/inorder/thread_context.hh
index 2dd55582e..a959d71d6 100644
--- a/src/cpu/inorder/thread_context.hh
+++ b/src/cpu/inorder/thread_context.hh
@@ -254,10 +254,10 @@ class InOrderThreadContext : public ThreadContext
     void setMiscReg(int misc_reg, const MiscReg &val);
 
     int flattenIntIndex(int reg)
-    { return cpu->isa[thread->threadId()].flattenIntIndex(reg); }
+    { return cpu->isa[thread->threadId()]->flattenIntIndex(reg); }
 
     int flattenFloatIndex(int reg)
-    { return cpu->isa[thread->threadId()].flattenFloatIndex(reg); }
+    { return cpu->isa[thread->threadId()]->flattenFloatIndex(reg); }
 
     void activateContext(Cycles delay)
     { cpu->activateContext(thread->threadId(), delay); }
diff --git a/src/cpu/o3/checker.cc b/src/cpu/o3/checker.cc
index c99428617..3ff3d86bc 100644
--- a/src/cpu/o3/checker.cc
+++ b/src/cpu/o3/checker.cc
@@ -82,6 +82,7 @@ O3CheckerParams::create()
 
     params->itb = itb;
     params->dtb = dtb;
+    params->isa = isa;
     params->system = system;
     params->cpu_id = cpu_id;
     params->profile = profile;
diff --git a/src/cpu/o3/cpu.cc b/src/cpu/o3/cpu.cc
index c5421302d..9de1bf6b4 100644
--- a/src/cpu/o3/cpu.cc
+++ b/src/cpu/o3/cpu.cc
@@ -241,6 +241,8 @@ FullO3CPU<Impl>::FullO3CPU(DerivO3CPUParams *params)
                  TheISA::NumMiscRegs * numThreads,
                  TheISA::ZeroReg),
 
+      isa(numThreads, NULL),
+
       icachePort(&fetch, this),
       dcachePort(&iew.ldstQueue, this),
 
@@ -340,6 +342,8 @@ FullO3CPU<Impl>::FullO3CPU(DerivO3CPUParams *params)
     for (ThreadID tid = 0; tid < numThreads; tid++) {
         bool bindRegs = (tid <= active_threads - 1);
 
+        isa[tid] = params->isa[tid];
+
         commitRenameMap[tid].init(TheISA::NumIntRegs,
                                   params->numPhysIntRegs,
                                   lreg_idx,            //Index for Logical. Regs
@@ -1285,7 +1289,7 @@ template <class Impl>
 TheISA::MiscReg
 FullO3CPU<Impl>::readMiscRegNoEffect(int misc_reg, ThreadID tid)
 {
-    return this->isa[tid].readMiscRegNoEffect(misc_reg);
+    return this->isa[tid]->readMiscRegNoEffect(misc_reg);
 }
 
 template <class Impl>
@@ -1293,7 +1297,7 @@ TheISA::MiscReg
 FullO3CPU<Impl>::readMiscReg(int misc_reg, ThreadID tid)
 {
     miscRegfileReads++;
-    return this->isa[tid].readMiscReg(misc_reg, tcBase(tid));
+    return this->isa[tid]->readMiscReg(misc_reg, tcBase(tid));
 }
 
 template <class Impl>
@@ -1301,7 +1305,7 @@ void
 FullO3CPU<Impl>::setMiscRegNoEffect(int misc_reg,
         const TheISA::MiscReg &val, ThreadID tid)
 {
-    this->isa[tid].setMiscRegNoEffect(misc_reg, val);
+    this->isa[tid]->setMiscRegNoEffect(misc_reg, val);
 }
 
 template <class Impl>
@@ -1310,7 +1314,7 @@ FullO3CPU<Impl>::setMiscReg(int misc_reg,
         const TheISA::MiscReg &val, ThreadID tid)
 {
     miscRegfileWrites++;
-    this->isa[tid].setMiscReg(misc_reg, val, tcBase(tid));
+    this->isa[tid]->setMiscReg(misc_reg, val, tcBase(tid));
 }
 
 template <class Impl>
diff --git a/src/cpu/o3/cpu.hh b/src/cpu/o3/cpu.hh
index 1f9a8da6c..06e1ea336 100644
--- a/src/cpu/o3/cpu.hh
+++ b/src/cpu/o3/cpu.hh
@@ -634,7 +634,7 @@ class FullO3CPU : public BaseO3CPU
     /** Integer Register Scoreboard */
     Scoreboard scoreboard;
 
-    TheISA::ISA isa[Impl::MaxThreads];
+    std::vector<TheISA::ISA *> isa;
 
     /** Instruction port. Note that it has to appear after the fetch stage. */
     IcachePort icachePort;
diff --git a/src/cpu/o3/thread_context_impl.hh b/src/cpu/o3/thread_context_impl.hh
index 38e7c5dec..9d60a9700 100755
--- a/src/cpu/o3/thread_context_impl.hh
+++ b/src/cpu/o3/thread_context_impl.hh
@@ -219,14 +219,14 @@ template <class Impl>
 void
 O3ThreadContext<Impl>::clearArchRegs()
 {
-    cpu->isa[thread->threadId()].clear();
+    cpu->isa[thread->threadId()]->clear();
 }
 
 template <class Impl>
 uint64_t
 O3ThreadContext<Impl>::readIntReg(int reg_idx)
 {
-    reg_idx = cpu->isa[thread->threadId()].flattenIntIndex(reg_idx);
+    reg_idx = cpu->isa[thread->threadId()]->flattenIntIndex(reg_idx);
     return cpu->readArchIntReg(reg_idx, thread->threadId());
 }
 
@@ -234,7 +234,7 @@ template <class Impl>
 TheISA::FloatReg
 O3ThreadContext<Impl>::readFloatReg(int reg_idx)
 {
-    reg_idx = cpu->isa[thread->threadId()].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[thread->threadId()]->flattenFloatIndex(reg_idx);
     return cpu->readArchFloatReg(reg_idx, thread->threadId());
 }
 
@@ -242,7 +242,7 @@ template <class Impl>
 TheISA::FloatRegBits
 O3ThreadContext<Impl>::readFloatRegBits(int reg_idx)
 {
-    reg_idx = cpu->isa[thread->threadId()].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[thread->threadId()]->flattenFloatIndex(reg_idx);
     return cpu->readArchFloatRegInt(reg_idx, thread->threadId());
 }
 
@@ -250,7 +250,7 @@ template <class Impl>
 void
 O3ThreadContext<Impl>::setIntReg(int reg_idx, uint64_t val)
 {
-    reg_idx = cpu->isa[thread->threadId()].flattenIntIndex(reg_idx);
+    reg_idx = cpu->isa[thread->threadId()]->flattenIntIndex(reg_idx);
     cpu->setArchIntReg(reg_idx, val, thread->threadId());
 
     conditionalSquash();
@@ -260,7 +260,7 @@ template <class Impl>
 void
 O3ThreadContext<Impl>::setFloatReg(int reg_idx, FloatReg val)
 {
-    reg_idx = cpu->isa[thread->threadId()].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[thread->threadId()]->flattenFloatIndex(reg_idx);
     cpu->setArchFloatReg(reg_idx, val, thread->threadId());
 
     conditionalSquash();
@@ -270,7 +270,7 @@ template <class Impl>
 void
 O3ThreadContext<Impl>::setFloatRegBits(int reg_idx, FloatRegBits val)
 {
-    reg_idx = cpu->isa[thread->threadId()].flattenFloatIndex(reg_idx);
+    reg_idx = cpu->isa[thread->threadId()]->flattenFloatIndex(reg_idx);
     cpu->setArchFloatRegInt(reg_idx, val, thread->threadId());
 
     conditionalSquash();
@@ -298,14 +298,14 @@ template <class Impl>
 int
 O3ThreadContext<Impl>::flattenIntIndex(int reg)
 {
-    return cpu->isa[thread->threadId()].flattenIntIndex(reg);
+    return cpu->isa[thread->threadId()]->flattenIntIndex(reg);
 }
 
 template <class Impl>
 int
 O3ThreadContext<Impl>::flattenFloatIndex(int reg)
 {
-    return cpu->isa[thread->threadId()].flattenFloatIndex(reg);
+    return cpu->isa[thread->threadId()]->flattenFloatIndex(reg);
 }
 
 template <class Impl>
diff --git a/src/cpu/ozone/checker_builder.cc b/src/cpu/ozone/checker_builder.cc
index f4bb03dcc..970591d33 100644
--- a/src/cpu/ozone/checker_builder.cc
+++ b/src/cpu/ozone/checker_builder.cc
@@ -89,6 +89,7 @@ OzoneCheckerParams::create()
 
     params->itb = itb;
     params->dtb = dtb;
+    params->isa = isa;
     params->system = system;
     params->cpu_id = cpu_id;
     params->profile = profile;
diff --git a/src/cpu/ozone/cpu_builder.cc b/src/cpu/ozone/cpu_builder.cc
index 65f68152f..ffd05375b 100644
--- a/src/cpu/ozone/cpu_builder.cc
+++ b/src/cpu/ozone/cpu_builder.cc
@@ -80,6 +80,7 @@ DerivOzoneCPUParams::create()
 
     params->itb = itb;
     params->dtb = dtb;
+    params->isa = isa;
 
     params->system = system;
     params->cpu_id = cpu_id;
diff --git a/src/cpu/ozone/simple_cpu_builder.cc b/src/cpu/ozone/simple_cpu_builder.cc
index 512dc3b9e..1fd9d3b79 100644
--- a/src/cpu/ozone/simple_cpu_builder.cc
+++ b/src/cpu/ozone/simple_cpu_builder.cc
@@ -83,6 +83,7 @@ SimpleOzoneCPUParams::create()
 
     params->itb = itb;
     params->dtb = dtb;
+    params->isa = isa;
 
     params->system = system;
     params->cpu_id = cpu_id;
diff --git a/src/cpu/simple/base.cc b/src/cpu/simple/base.cc
index 9ca943900..da965450a 100644
--- a/src/cpu/simple/base.cc
+++ b/src/cpu/simple/base.cc
@@ -87,10 +87,11 @@ BaseSimpleCPU::BaseSimpleCPU(BaseSimpleCPUParams *p)
     : BaseCPU(p), traceData(NULL), thread(NULL)
 {
     if (FullSystem)
-        thread = new SimpleThread(this, 0, p->system, p->itb, p->dtb);
+        thread = new SimpleThread(this, 0, p->system, p->itb, p->dtb,
+                                  p->isa[0]);
     else
         thread = new SimpleThread(this, /* thread_num */ 0, p->system,
-                p->workload[0], p->itb, p->dtb);
+                                  p->workload[0], p->itb, p->dtb, p->isa[0]);
 
     thread->setStatus(ThreadContext::Halted);
 
diff --git a/src/cpu/simple_thread.cc b/src/cpu/simple_thread.cc
index cf9bb4840..af121e43f 100644
--- a/src/cpu/simple_thread.cc
+++ b/src/cpu/simple_thread.cc
@@ -61,9 +61,9 @@ using namespace std;
 // constructor
 SimpleThread::SimpleThread(BaseCPU *_cpu, int _thread_num, System *_sys,
                            Process *_process, TheISA::TLB *_itb,
-                           TheISA::TLB *_dtb)
-    : ThreadState(_cpu, _thread_num, _process), system(_sys), itb(_itb),
-      dtb(_dtb)
+                           TheISA::TLB *_dtb, TheISA::ISA *_isa)
+    : ThreadState(_cpu, _thread_num, _process), isa(_isa), system(_sys),
+      itb(_itb), dtb(_dtb)
 {
     clearArchRegs();
     tc = new ProxyThreadContext<SimpleThread>(this);
@@ -71,8 +71,9 @@ SimpleThread::SimpleThread(BaseCPU *_cpu, int _thread_num, System *_sys,
 
 SimpleThread::SimpleThread(BaseCPU *_cpu, int _thread_num, System *_sys,
                            TheISA::TLB *_itb, TheISA::TLB *_dtb,
-                           bool use_kernel_stats)
-    : ThreadState(_cpu, _thread_num, NULL), system(_sys), itb(_itb), dtb(_dtb)
+                           TheISA::ISA *_isa, bool use_kernel_stats)
+    : ThreadState(_cpu, _thread_num, NULL), isa(_isa), system(_sys), itb(_itb),
+      dtb(_dtb)
 {
     tc = new ProxyThreadContext<SimpleThread>(this);
 
@@ -99,7 +100,7 @@ SimpleThread::SimpleThread(BaseCPU *_cpu, int _thread_num, System *_sys,
 }
 
 SimpleThread::SimpleThread()
-    : ThreadState(NULL, -1, NULL)
+    : ThreadState(NULL, -1, NULL), isa(NULL)
 {
     tc = new ProxyThreadContext<SimpleThread>(this);
 }
@@ -182,7 +183,7 @@ SimpleThread::serialize(ostream &os)
     // 
     // Now must serialize all the ISA dependent state
     //
-    isa.serialize(baseCpu, os);
+    isa->serialize(baseCpu, os);
 }
 
 
@@ -198,7 +199,7 @@ SimpleThread::unserialize(Checkpoint *cp, const std::string &section)
     // 
     // Now must unserialize all the ISA dependent state
     //
-    isa.unserialize(baseCpu, cp, section);
+    isa->unserialize(baseCpu, cp, section);
 }
 
 void
diff --git a/src/cpu/simple_thread.hh b/src/cpu/simple_thread.hh
index 8594e4471..8e6df9466 100644
--- a/src/cpu/simple_thread.hh
+++ b/src/cpu/simple_thread.hh
@@ -108,7 +108,7 @@ class SimpleThread : public ThreadState
         FloatRegBits i[TheISA::NumFloatRegs];
     } floatRegs;
     TheISA::IntReg intRegs[TheISA::NumIntRegs];
-    TheISA::ISA isa;    // one "instance" of the current ISA.
+    TheISA::ISA *const isa;    // one "instance" of the current ISA.
 
     TheISA::PCState _pcState;
 
@@ -133,11 +133,12 @@ class SimpleThread : public ThreadState
     // constructor: initialize SimpleThread from given process structure
     // FS
     SimpleThread(BaseCPU *_cpu, int _thread_num, System *_system,
-                 TheISA::TLB *_itb, TheISA::TLB *_dtb,
+                 TheISA::TLB *_itb, TheISA::TLB *_dtb, TheISA::ISA *_isa,
                  bool use_kernel_stats = true);
     // SE
     SimpleThread(BaseCPU *_cpu, int _thread_num, System *_system,
-                 Process *_process, TheISA::TLB *_itb, TheISA::TLB *_dtb);
+                 Process *_process, TheISA::TLB *_itb, TheISA::TLB *_dtb,
+                 TheISA::ISA *_isa);
 
     SimpleThread();
 
@@ -226,7 +227,7 @@ class SimpleThread : public ThreadState
         _pcState = 0;
         memset(intRegs, 0, sizeof(intRegs));
         memset(floatRegs.i, 0, sizeof(floatRegs.i));
-        isa.clear();
+        isa->clear();
     }
 
     //
@@ -234,7 +235,7 @@ class SimpleThread : public ThreadState
     //
     uint64_t readIntReg(int reg_idx)
     {
-        int flatIndex = isa.flattenIntIndex(reg_idx);
+        int flatIndex = isa->flattenIntIndex(reg_idx);
         assert(flatIndex < TheISA::NumIntRegs);
         uint64_t regVal = intRegs[flatIndex];
         DPRINTF(IntRegs, "Reading int reg %d (%d) as %#x.\n",
@@ -244,7 +245,7 @@ class SimpleThread : public ThreadState
 
     FloatReg readFloatReg(int reg_idx)
     {
-        int flatIndex = isa.flattenFloatIndex(reg_idx);
+        int flatIndex = isa->flattenFloatIndex(reg_idx);
         assert(flatIndex < TheISA::NumFloatRegs);
         FloatReg regVal = floatRegs.f[flatIndex];
         DPRINTF(FloatRegs, "Reading float reg %d (%d) as %f, %#x.\n",
@@ -254,7 +255,7 @@ class SimpleThread : public ThreadState
 
     FloatRegBits readFloatRegBits(int reg_idx)
     {
-        int flatIndex = isa.flattenFloatIndex(reg_idx);
+        int flatIndex = isa->flattenFloatIndex(reg_idx);
         assert(flatIndex < TheISA::NumFloatRegs);
         FloatRegBits regVal = floatRegs.i[flatIndex];
         DPRINTF(FloatRegs, "Reading float reg %d (%d) bits as %#x, %f.\n",
@@ -264,7 +265,7 @@ class SimpleThread : public ThreadState
 
     void setIntReg(int reg_idx, uint64_t val)
     {
-        int flatIndex = isa.flattenIntIndex(reg_idx);
+        int flatIndex = isa->flattenIntIndex(reg_idx);
         assert(flatIndex < TheISA::NumIntRegs);
         DPRINTF(IntRegs, "Setting int reg %d (%d) to %#x.\n",
                 reg_idx, flatIndex, val);
@@ -273,7 +274,7 @@ class SimpleThread : public ThreadState
 
     void setFloatReg(int reg_idx, FloatReg val)
     {
-        int flatIndex = isa.flattenFloatIndex(reg_idx);
+        int flatIndex = isa->flattenFloatIndex(reg_idx);
         assert(flatIndex < TheISA::NumFloatRegs);
         floatRegs.f[flatIndex] = val;
         DPRINTF(FloatRegs, "Setting float reg %d (%d) to %f, %#x.\n",
@@ -282,7 +283,7 @@ class SimpleThread : public ThreadState
 
     void setFloatRegBits(int reg_idx, FloatRegBits val)
     {
-        int flatIndex = isa.flattenFloatIndex(reg_idx);
+        int flatIndex = isa->flattenFloatIndex(reg_idx);
         assert(flatIndex < TheISA::NumFloatRegs);
         // XXX: Fix array out of bounds compiler error for gem5.fast
         // when checkercpu enabled
@@ -341,37 +342,37 @@ class SimpleThread : public ThreadState
     MiscReg
     readMiscRegNoEffect(int misc_reg, ThreadID tid = 0)
     {
-        return isa.readMiscRegNoEffect(misc_reg);
+        return isa->readMiscRegNoEffect(misc_reg);
     }
 
     MiscReg
     readMiscReg(int misc_reg, ThreadID tid = 0)
     {
-        return isa.readMiscReg(misc_reg, tc);
+        return isa->readMiscReg(misc_reg, tc);
     }
 
     void
     setMiscRegNoEffect(int misc_reg, const MiscReg &val, ThreadID tid = 0)
     {
-        return isa.setMiscRegNoEffect(misc_reg, val);
+        return isa->setMiscRegNoEffect(misc_reg, val);
     }
 
     void
     setMiscReg(int misc_reg, const MiscReg &val, ThreadID tid = 0)
     {
-        return isa.setMiscReg(misc_reg, val, tc);
+        return isa->setMiscReg(misc_reg, val, tc);
     }
 
     int
     flattenIntIndex(int reg)
     {
-        return isa.flattenIntIndex(reg);
+        return isa->flattenIntIndex(reg);
     }
 
     int
     flattenFloatIndex(int reg)
     {
-        return isa.flattenFloatIndex(reg);
+        return isa->flattenFloatIndex(reg);
     }
 
     unsigned readStCondFailures() { return storeCondFailures; }