Use functions to access XC.

cpu/exec_context.hh:
    Include readNextNPC function.
cpu/simple/cpu.cc:
    Use functions to set and access nextPC, nextNPC.

--HG--
extra : convert_revision : 22622b9c110e1d99cc9106a2a27c479579d7e1ad

cpu/exec_context.hh

@@ -422,6 +422,11 @@ class ExecContext
         regs.npc = val;
     }
 
+    uint64_t readNextNPC()
+    {
+        return regs.nnpc;
+    }
+
     void setNextNPC(uint64_t val)
     {
         regs.nnpc = val;

cpu/simple/cpu.cc

@@ -825,8 +825,8 @@ SimpleCPU::tick()
 #else
         // go to the next instruction
         xc->regs.pc = xc->regs.npc;
-        xc->regs.npc = xc->regs.nnpc;
-        xc->regs.nnpc += sizeof(MachInst);
+        xc->setNextPC(xc->readNextNPC());
+        xc->setNextNPC(xc->readNextNPC() + sizeof(MachInst));
 #endif
 
     }