Optimize Atari emulator by ~30%

src/emucore/Console.cxx

@@ -148,7 +148,7 @@ Console::Console(OSystem* osystem, Cartridge* cart, const Properties& props)
   mySwitches = new Switches(*myEvent, myProperties);
 
   // Now, we can construct the system and components
-  mySystem = new System(13, 6);
+  mySystem = new System();
 
   // Inform the controllers about the system
   myControllers[0]->setSystem(mySystem);

src/emucore/m6502/src/System.cxx

@@ -28,20 +28,13 @@
 using namespace std;
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-System::System(uInt16 n, uInt16 m)
-  : myAddressMask((1 << n) - 1),
-    myPageShift(m),
-    myPageMask((1 << m) - 1),
-    myNumberOfPages(1 << (n - m)),
-    myNumberOfDevices(0),
+System::System()
+  : myNumberOfDevices(0),
     myM6502(0),
     myTIA(0),
     myCycles(0),
     myDataBusState(0)
 {
-  // Make sure the arguments are reasonable
-  assert((1 <= m) && (m <= n) && (n <= 16));
-
   // Allocate page table
   myPageAccessTable = new PageAccess[myNumberOfPages];
 
@@ -285,12 +278,7 @@ bool System::loadState(const string& md5sum, Deserializer& in)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-System::System(const System& s)
-  : myAddressMask(s.myAddressMask),
-    myPageShift(s.myPageShift),
-    myPageMask(s.myPageMask),
-    myNumberOfPages(s.myNumberOfPages)
-{
+System::System(const System& s) {
   assert(false);
 }
 
@@ -302,52 +290,6 @@ System& System::operator = (const System&)
   return *this;
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-uInt8 System::peek(uInt16 addr) 
-{
-  PageAccess& access = myPageAccessTable[(addr & myAddressMask) >> myPageShift];
-
-  uInt8 result;
-
-  // See if this page uses direct accessing or not 
-  if(access.directPeekBase != 0)
-  {
-    result = *(access.directPeekBase + (addr & myPageMask));
-  }
-  else
-  {
-    result = access.device->peek(addr);
-  }
-
-#ifdef DEBUGGER_SUPPORT
-  if(!myDataBusLocked)
-#endif
-    myDataBusState = result;
-
-  return result;
-}
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void System::poke(uInt16 addr, uInt8 value)
-{
-  PageAccess& access = myPageAccessTable[(addr & myAddressMask) >> myPageShift];
-
-  // See if this page uses direct accessing or not 
-  if(access.directPokeBase != 0)
-  {
-    *(access.directPokeBase + (addr & myPageMask)) = value;
-  }
-  else
-  {
-    access.device->poke(addr, value);
-  }
-
-#ifdef DEBUGGER_SUPPORT
-  if(!myDataBusLocked)
-#endif
-    myDataBusState = value;
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void System::lockDataBus()
 {

src/emucore/m6502/src/System.hxx

@@ -53,13 +53,10 @@ class System
 {
   public:
     /**
-      Create a new system with an addressing space of 2^n bytes and
-      pages of 2^m bytes.
-
-      @param n Log base 2 of the addressing space size
-      @param m Log base 2 of the page size
+      Create a new system with an addressing space of 2^13 bytes and
+      pages of 2^6 bytes.
     */
-    System(uInt16 n, uInt16 m);
+    System();
 
     /**
       Destructor
@@ -187,7 +184,7 @@ class System
     */
     uInt16 pageShift() const
     {
-      return myPageShift;
+      return myPageSize;
     }
 
     /**
@@ -246,17 +243,57 @@ class System
 
       @return The byte at the specified address
     */
-    uInt8 peek(uInt16 address);
+    inline uInt8 peek(uInt16 addr)
+    {
+      PageAccess& access = myPageAccessTable[(addr & myAddressMask) >> myPageSize];
+
+      uInt8 result;
+
+      // See if this page uses direct accessing or not
+      if(access.directPeekBase != 0)
+      {
+        result = *(access.directPeekBase + (addr & myPageMask));
+      }
+      else
+      {
+        result = access.device->peek(addr);
+      }
+
+    #ifdef DEBUGGER_SUPPORT
+      if(!myDataBusLocked)
+    #endif
+        myDataBusState = result;
+
+      return result;
+    }
 
     /**
       Change the byte at the specified address to the given value.
       No masking of the address occurs before it's sent to the device
       mapped at the address.
 
-      @param address The address where the value should be stored
+      @param addr The address where the value should be stored
       @param value The value to be stored at the address
     */
-    void poke(uInt16 address, uInt8 value);
+    inline void poke(uInt16 addr, uInt8 value) {
+      PageAccess& access = myPageAccessTable[
+          (addr & myAddressMask) >> myPageSize];
+
+      // See if this page uses direct accessing or not
+      if(access.directPokeBase != 0)
+      {
+        *(access.directPokeBase + (addr & myPageMask)) = value;
+      }
+      else
+      {
+        access.device->poke(addr, value);
+      }
+
+    #ifdef DEBUGGER_SUPPORT
+      if(!myDataBusLocked)
+    #endif
+        myDataBusState = value;
+    }
 
     /**
       Lock/unlock the data bus. When the bus is locked, peek() and
@@ -316,17 +353,20 @@ class System
     const PageAccess& getPageAccess(uInt16 page);
 
   private:
-    // Mask to apply to an address before accessing memory
-    const uInt16 myAddressMask;
+    // Log base 2 of the addressing space size.
+    static constexpr uInt16 myAddressingSpace = 13;
+
+    // Log base 2 of the page size.
+    static constexpr uInt16 myPageSize = 6;
 
-    // Amount to shift an address by to determine what page it's on
-    const uInt16 myPageShift;
+    // Mask to apply to an address before accessing memory
+    static constexpr uInt16 myAddressMask = (1 << myAddressingSpace) - 1;
 
     // Mask to apply to an address to obtain its page offset
-    const uInt16 myPageMask;
+    static constexpr uInt16 myPageMask = (1 << myPageSize) - 1;
 
     // Number of pages in the system
-    const uInt16 myNumberOfPages;
+    static constexpr uInt16 myNumberOfPages = 1 << (myAddressingSpace - myPageSize);
 
     // Pointer to a dynamically allocated array of PageAccess structures
     PageAccess* myPageAccessTable;