MEM: Make port proxies use references rather than pointers

This patch is adding a clearer design intent to all objects that would
not be complete without a port proxy by making the proxies members
rathen than dynamically allocated. In essence, if NULL would not be a
valid value for the proxy, then we avoid using a pointer to make this
clear.

The same approach is used for the methods using these proxies, such as
loadSections, that now use references rather than pointers to better
reflect the fact that NULL would not be an acceptable value (in fact
the code would break and that is how this patch started out).

Overall the concept of "using a reference to express unconditional
composition where a NULL pointer is never valid" could be done on a
much broader scale throughout the code base, but for now it is only
done in the locations affected by the proxies.

10 files changed, 34 insertions, 46 deletions

diff --git a/src/cpu/checker/thread_context.hh b/src/cpu/checker/thread_context.hh
index d21de9f53..0d6fa6e2e 100644
--- a/src/cpu/checker/thread_context.hh
+++ b/src/cpu/checker/thread_context.hh
@@ -125,9 +125,9 @@ class CheckerThreadContext : public ThreadContext
 
     Process *getProcessPtr() { return actualTC->getProcessPtr(); }
 
-    PortProxy* getPhysProxy() { return actualTC->getPhysProxy(); }
+    PortProxy &getPhysProxy() { return actualTC->getPhysProxy(); }
 
-    FSTranslatingPortProxy* getVirtProxy()
+    FSTranslatingPortProxy &getVirtProxy()
     { return actualTC->getVirtProxy(); }
 
     //XXX: How does this work now?
@@ -139,7 +139,7 @@ class CheckerThreadContext : public ThreadContext
         actualTC->connectMemPorts(tc);
     }
 
-    SETranslatingPortProxy* getMemProxy() { return actualTC->getMemProxy(); }
+    SETranslatingPortProxy &getMemProxy() { return actualTC->getMemProxy(); }
 
     /** Executes a syscall in SE mode. */
     void syscall(int64_t callnum)
diff --git a/src/cpu/inorder/thread_context.cc b/src/cpu/inorder/thread_context.cc
index 1a7ac0890..72592c299 100644
--- a/src/cpu/inorder/thread_context.cc
+++ b/src/cpu/inorder/thread_context.cc
@@ -38,7 +38,7 @@
 
 using namespace TheISA;
 
-FSTranslatingPortProxy*
+FSTranslatingPortProxy&
 InOrderThreadContext::getVirtProxy()
 {
     return thread->getVirtProxy();
diff --git a/src/cpu/inorder/thread_context.hh b/src/cpu/inorder/thread_context.hh
index 5a9cfce32..0f9b1028e 100644
--- a/src/cpu/inorder/thread_context.hh
+++ b/src/cpu/inorder/thread_context.hh
@@ -115,9 +115,9 @@ class InOrderThreadContext : public ThreadContext
     TheISA::Kernel::Statistics *getKernelStats()
     { return thread->kernelStats; }
 
-    PortProxy* getPhysProxy() { return thread->getPhysProxy(); }
+    PortProxy &getPhysProxy() { return thread->getPhysProxy(); }
 
-    FSTranslatingPortProxy* getVirtProxy();
+    FSTranslatingPortProxy &getVirtProxy();
 
     void initMemProxies(ThreadContext *tc)
     { thread->initMemProxies(tc); }
@@ -144,7 +144,7 @@ class InOrderThreadContext : public ThreadContext
         return this->thread->quiesceEvent;
     }
 
-    SETranslatingPortProxy* getMemProxy() { return thread->getMemProxy(); }
+    SETranslatingPortProxy &getMemProxy() { return thread->getMemProxy(); }
 
     /** Returns a pointer to this thread's process. */
     Process *getProcessPtr() { return thread->getProcessPtr(); }
diff --git a/src/cpu/o3/thread_context.hh b/src/cpu/o3/thread_context.hh
index c2096fab2..8c32d1c05 100755
--- a/src/cpu/o3/thread_context.hh
+++ b/src/cpu/o3/thread_context.hh
@@ -114,14 +114,14 @@ class O3ThreadContext : public ThreadContext
     /** Returns a pointer to this thread's process. */
     virtual Process *getProcessPtr() { return thread->getProcessPtr(); }
 
-    virtual PortProxy* getPhysProxy() { return thread->getPhysProxy(); }
+    virtual PortProxy &getPhysProxy() { return thread->getPhysProxy(); }
 
-    virtual FSTranslatingPortProxy* getVirtProxy();
+    virtual FSTranslatingPortProxy &getVirtProxy();
 
     virtual void initMemProxies(ThreadContext *tc)
     { thread->initMemProxies(tc); }
 
-    virtual SETranslatingPortProxy* getMemProxy()
+    virtual SETranslatingPortProxy &getMemProxy()
     { return thread->getMemProxy(); }
 
     /** Returns this thread's status. */
diff --git a/src/cpu/o3/thread_context_impl.hh b/src/cpu/o3/thread_context_impl.hh
index 2ea39f3eb..ecc40bd14 100755
--- a/src/cpu/o3/thread_context_impl.hh
+++ b/src/cpu/o3/thread_context_impl.hh
@@ -50,7 +50,7 @@
 #include "debug/O3CPU.hh"
 
 template <class Impl>
-FSTranslatingPortProxy*
+FSTranslatingPortProxy&
 O3ThreadContext<Impl>::getVirtProxy()
 {
     return thread->getVirtProxy();
diff --git a/src/cpu/ozone/cpu.hh b/src/cpu/ozone/cpu.hh
index ff43ad6cb..d2b90bff3 100644
--- a/src/cpu/ozone/cpu.hh
+++ b/src/cpu/ozone/cpu.hh
@@ -114,12 +114,12 @@ class OzoneCPU : public BaseCPU
 
         Process *getProcessPtr() { return thread->getProcessPtr(); }
 
-        PortProxy* getPhysProxy() { return thread->getPhysProxy(); }
+        PortProxy &getPhysProxy() { return thread->getPhysProxy(); }
 
-        FSTranslatingPortProxy* getVirtProxy()
+        FSTranslatingPortProxy &getVirtProxy()
         { return thread->getVirtProxy(); }
 
-        SETranslatingPortProxy* getMemProxy() { return thread->getMemProxy(); }
+        SETranslatingPortProxy &getMemProxy() { return thread->getMemProxy(); }
 
         Status status() const { return thread->status(); }
 
diff --git a/src/cpu/simple_thread.hh b/src/cpu/simple_thread.hh
index b6dc8f047..d12ee9a06 100644
--- a/src/cpu/simple_thread.hh
+++ b/src/cpu/simple_thread.hh
@@ -206,14 +206,6 @@ class SimpleThread : public ThreadState
 
     System *getSystemPtr() { return system; }
 
-    PortProxy* getPhysProxy() { return physProxy; }
-
-    /** Return a virtual port. This port cannot be cached locally in an object.
-     * After a CPU switch it may point to the wrong memory object which could
-     * mean stale data.
-     */
-    FSTranslatingPortProxy* getVirtProxy() { return virtProxy; }
-
     Status status() const { return _status; }
 
     void setStatus(Status newStatus) { _status = newStatus; }
diff --git a/src/cpu/thread_context.hh b/src/cpu/thread_context.hh
index 2f2e5b02b..41941b262 100644
--- a/src/cpu/thread_context.hh
+++ b/src/cpu/thread_context.hh
@@ -143,9 +143,9 @@ class ThreadContext
 
     virtual TheISA::Kernel::Statistics *getKernelStats() = 0;
 
-    virtual PortProxy* getPhysProxy() = 0;
+    virtual PortProxy &getPhysProxy() = 0;
 
-    virtual FSTranslatingPortProxy* getVirtProxy() = 0;
+    virtual FSTranslatingPortProxy &getVirtProxy() = 0;
 
     /**
      * Initialise the physical and virtual port proxies and tie them to
@@ -155,7 +155,7 @@ class ThreadContext
      */
     virtual void initMemProxies(ThreadContext *tc) = 0;
 
-    virtual SETranslatingPortProxy *getMemProxy() = 0;
+    virtual SETranslatingPortProxy &getMemProxy() = 0;
 
     virtual Process *getProcessPtr() = 0;
 
@@ -319,13 +319,13 @@ class ProxyThreadContext : public ThreadContext
     TheISA::Kernel::Statistics *getKernelStats()
     { return actualTC->getKernelStats(); }
 
-    PortProxy* getPhysProxy() { return actualTC->getPhysProxy(); }
+    PortProxy &getPhysProxy() { return actualTC->getPhysProxy(); }
 
-    FSTranslatingPortProxy* getVirtProxy() { return actualTC->getVirtProxy(); }
+    FSTranslatingPortProxy &getVirtProxy() { return actualTC->getVirtProxy(); }
 
     void initMemProxies(ThreadContext *tc) { actualTC->initMemProxies(tc); }
 
-    SETranslatingPortProxy* getMemProxy() { return actualTC->getMemProxy(); }
+    SETranslatingPortProxy &getMemProxy() { return actualTC->getMemProxy(); }
 
     Process *getProcessPtr() { return actualTC->getProcessPtr(); }
 
diff --git a/src/cpu/thread_state.cc b/src/cpu/thread_state.cc
index 33c0d719c..3d58b4da4 100644
--- a/src/cpu/thread_state.cc
+++ b/src/cpu/thread_state.cc
@@ -106,6 +106,9 @@ ThreadState::initMemProxies(ThreadContext *tc)
     // (i.e. due to restoring from a checkpoint and later switching
     // in.
     if (physProxy == NULL)
+        // this cannot be done in the constructor as the thread state
+        // itself is created in the base cpu constructor and the
+        // getPort is a virtual function at the moment
         physProxy = new PortProxy(baseCpu->getDataPort());
     if (virtProxy == NULL)
         virtProxy = new FSTranslatingPortProxy(tc);
@@ -125,16 +128,12 @@ ThreadState::profileSample()
         profile->sample(profileNode, profilePC);
 }
 
-SETranslatingPortProxy *
+SETranslatingPortProxy &
 ThreadState::getMemProxy()
 {
-    if (proxy != NULL)
-        return proxy;
-
-    /* Use this port proxy to for syscall emulation writes to memory. */
-    proxy = new SETranslatingPortProxy(*process->system->getSystemPort(),
-                                       process,
-                                       SETranslatingPortProxy::NextPage);
-
-    return proxy;
+    if (proxy == NULL)
+        proxy = new SETranslatingPortProxy(baseCpu->getDataPort(),
+                                           process,
+                                           SETranslatingPortProxy::NextPage);
+    return *proxy;
 }
diff --git a/src/cpu/thread_state.hh b/src/cpu/thread_state.hh
index d1ce83803..153049812 100644
--- a/src/cpu/thread_state.hh
+++ b/src/cpu/thread_state.hh
@@ -49,9 +49,6 @@ namespace TheISA {
 };
 
 class Checkpoint;
-class PortProxy;
-class SETranslatingPort;
-class FSTranslatingPort;
 
 /**
  *  Struct for holding general thread state that is needed across CPU
@@ -102,13 +99,13 @@ struct ThreadState {
 
     TheISA::Kernel::Statistics *getKernelStats() { return kernelStats; }
 
-    PortProxy* getPhysProxy() { return physProxy; }
+    PortProxy &getPhysProxy() { return *physProxy; }
 
-    FSTranslatingPortProxy* getVirtProxy() { return virtProxy; }
+    FSTranslatingPortProxy &getVirtProxy() { return *virtProxy; }
 
     Process *getProcessPtr() { return process; }
 
-    SETranslatingPortProxy* getMemProxy();
+    SETranslatingPortProxy &getMemProxy();
 
     /** Reads the number of instructions functionally executed and
      * committed.
@@ -183,8 +180,8 @@ struct ThreadState {
 
     /** A translating port proxy, outgoing only, for functional
      * accesse to virtual addresses. */
-    FSTranslatingPortProxy* virtProxy;
-    SETranslatingPortProxy* proxy;
+    FSTranslatingPortProxy *virtProxy;
+    SETranslatingPortProxy *proxy;
 
   public:
     /*