Make Register16 a class, rather than struct. Tricky, but a bit faster than before.

Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>

EightBit/BigEndianProcessor.cs

@@ -33,7 +33,7 @@ namespace EightBit
         protected override Register16 GetWord()
         {
             var high = this.BusRead();
-            ++this.Bus.Address();
+            ++this.Bus.Address.Word;
             var low = this.BusRead();
             return new Register16(low, high);
         }
@@ -61,7 +61,7 @@ namespace EightBit
         protected override void SetWord(Register16 value)
         {
             this.BusWrite(value.High);
-            ++this.Bus.Address();
+            ++this.Bus.Address.Word;
             this.BusWrite(value.Low);
         }
 

EightBit/Bus.cs

@@ -8,7 +8,6 @@ namespace EightBit
 
     public abstract class Bus : IMapper
     {
-        private Register16 address;
         private byte data;
 
         public event EventHandler<EventArgs> WritingByte;
@@ -21,7 +20,7 @@ namespace EightBit
 
         public byte Data { get => this.data; set => this.data = value; }
 
-        public ref Register16 Address() => ref this.address;
+        public Register16 Address { get; } = new Register16();
 
         public abstract MemoryMapping Mapping(ushort absolute);
 
@@ -51,7 +50,7 @@ namespace EightBit
 
         public byte Read(ushort absolute)
         {
-            this.Address().Word = absolute;
+            this.Address.Word = absolute;
             return this.Read();
         }
 
@@ -59,8 +58,8 @@ namespace EightBit
 
         public byte Read(byte low, byte high)
         {
-            this.Address().Low = low;
-            this.Address().High = high;
+            this.Address.Low = low;
+            this.Address.High = high;
             return this.Read();
         }
 
@@ -79,7 +78,7 @@ namespace EightBit
 
         public void Write(ushort absolute, byte value)
         {
-            this.Address().Word = absolute;
+            this.Address.Word = absolute;
             this.Write(value);
         }
 
@@ -87,8 +86,8 @@ namespace EightBit
 
         public void Write(byte low, byte high, byte value)
         {
-            this.Address().Low = low;
-            this.Address().High = high;
+            this.Address.Low = low;
+            this.Address.High = high;
             this.Write(value);
         }
 
@@ -125,7 +124,7 @@ namespace EightBit
 
         protected ref byte Reference(Register16 absolute) => ref this.Reference(absolute.Word);
 
-        protected ref byte Reference() => ref this.Reference(this.Address());
+        protected ref byte Reference() => ref this.Reference(this.Address);
 
         protected ref byte Reference(byte low, byte high) => ref this.Reference(new Register16(low, high).Word);
 

EightBit/IntelProcessor.cs

@@ -13,10 +13,6 @@ namespace EightBit
 
         private readonly IntelOpCodeDecoded[] decodedOpCodes = new IntelOpCodeDecoded[0x100];
 
-        private Register16 sp = new Register16((ushort)Mask.Mask16);
-
-        private Register16 memptr = new Register16((ushort)Mask.Mask16);
-
         private PinLevel haltLine;
 
         protected IntelProcessor(Bus bus)
@@ -36,36 +32,36 @@ namespace EightBit
 
         public event EventHandler<EventArgs> LoweredHALT;
 
+        public Register16 SP { get; } = new Register16((ushort)Mask.Mask16);
+
+        public Register16 MEMPTR { get; } = new Register16((ushort)Mask.Mask16);
+
+        public abstract Register16 AF { get; }
+
+        public byte A { get => this.AF.High; set => this.AF.High = value; }
+
+        public byte F { get => this.AF.Low; set => this.AF.Low = value; }
+
+        public abstract Register16 BC { get; }
+
+        public byte B { get => this.BC.High; set => this.BC.High = value; }
+
+        public byte C { get => this.BC.Low; set => this.BC.Low = value; }
+
+        public abstract Register16 DE { get; }
+
+        public byte D { get => this.DE.High; set => this.DE.High = value; }
+
+        public byte E { get => this.DE.Low; set => this.DE.Low = value; }
+
+        public abstract Register16 HL { get; }
+
+        public byte H { get => this.HL.High; set => this.HL.High = value; }
+
+        public byte L { get => this.HL.Low; set => this.HL.Low = value; }
+
         protected bool Halted => this.HALT().Lowered();
 
-        public ref Register16 SP() => ref this.sp;
-
-        public ref Register16 MEMPTR() => ref this.memptr;
-
-        public abstract ref Register16 AF();
-
-        public ref byte A() => ref this.AF().High;
-
-        public ref byte F() => ref this.AF().Low;
-
-        public abstract ref Register16 BC();
-
-        public ref byte B() => ref this.BC().High;
-
-        public ref byte C() => ref this.BC().Low;
-
-        public abstract ref Register16 DE();
-
-        public ref byte D() => ref this.DE().High;
-
-        public ref byte E() => ref this.DE().Low;
-
-        public abstract ref Register16 HL();
-
-        public ref byte H() => ref this.HL().High;
-
-        public ref byte L() => ref this.HL().Low;
-
         public ref PinLevel HALT() => ref this.haltLine;
 
         public IntelOpCodeDecoded GetDecodedOpCode(byte opCode) => this.decodedOpCodes[opCode];
@@ -74,7 +70,7 @@ namespace EightBit
         {
             base.RaisePOWER();
             this.RaiseHALT();
-            this.SP().Word = this.AF().Word = this.BC().Word = this.DE().Word = this.HL().Word = (ushort)Mask.Mask16;
+            this.SP.Word = this.AF.Word = this.BC.Word = this.DE.Word = this.HL.Word = (ushort)Mask.Mask16;
         }
 
         public virtual void RaiseHALT()
@@ -122,38 +118,38 @@ namespace EightBit
             this.Jump(0);
         }
 
-        protected sealed override void Push(byte value) => this.Bus.Write(--this.SP(), value);
+        protected sealed override void Push(byte value) => this.Bus.Write(--this.SP.Word, value);
 
-        protected sealed override byte Pop() => this.Bus.Read(this.SP()++);
+        protected sealed override byte Pop() => this.Bus.Read(this.SP.Word++);
 
         protected sealed override Register16 GetWord()
         {
             var returned = base.GetWord();
-            this.MEMPTR().Word = this.Bus.Address().Word;
+            this.MEMPTR.Word = this.Bus.Address.Word;
             return returned;
         }
 
         protected sealed override void SetWord(Register16 value)
         {
             base.SetWord(value);
-            this.MEMPTR().Word = this.Bus.Address().Word;
+            this.MEMPTR.Word = this.Bus.Address.Word;
         }
 
         ////
 
         protected void Restart(byte address)
         {
-            this.MEMPTR().Low = address;
-            this.MEMPTR().High = 0;
-            this.Call(this.MEMPTR());
+            this.MEMPTR.Low = address;
+            this.MEMPTR.High = 0;
+            this.Call(this.MEMPTR);
         }
 
         protected bool CallConditional(bool condition)
         {
-            this.MEMPTR().Word = this.FetchWord().Word;
+            this.MEMPTR.Word = this.FetchWord().Word;
             if (condition)
             {
-                this.Call(this.MEMPTR());
+                this.Call(this.MEMPTR);
             }
 
             return condition;
@@ -161,10 +157,10 @@ namespace EightBit
 
         protected bool JumpConditional(bool condition)
         {
-            this.MEMPTR().Word = this.FetchWord().Word;
+            this.MEMPTR.Word = this.FetchWord().Word;
             if (condition)
             {
-                this.Jump(this.MEMPTR());
+                this.Jump(this.MEMPTR);
             }
 
             return condition;
@@ -182,8 +178,8 @@ namespace EightBit
 
         protected void JumpRelative(sbyte offset)
         {
-            this.MEMPTR().Word = (ushort)(this.PC().Word + offset);
-            this.Jump(this.MEMPTR());
+            this.MEMPTR.Word = (ushort)(this.PC.Word + offset);
+            this.Jump(this.MEMPTR);
         }
 
         protected bool JumpRelativeConditional(bool condition)
@@ -200,18 +196,18 @@ namespace EightBit
         protected override sealed void Return()
         {
             base.Return();
-            this.MEMPTR().Word = this.PC().Word;
+            this.MEMPTR.Word = this.PC.Word;
         }
 
         protected void Halt()
         {
-            --this.PC();
+            --this.PC.Word;
             this.LowerHALT();
         }
 
         protected void Proceed()
         {
-            ++this.PC();
+            ++this.PC.Word;
             this.RaiseHALT();
         }
     }

EightBit/LittleEndianProcessor.cs

@@ -34,7 +34,7 @@ namespace EightBit
         protected override Register16 GetWord()
         {
             var low = this.BusRead();
-            ++this.Bus.Address();
+            ++this.Bus.Address.Word;
             var high = this.BusRead();
             return new Register16(low, high);
         }
@@ -62,7 +62,7 @@ namespace EightBit
         protected override void SetWord(Register16 value)
         {
             this.BusWrite(value.Low);
-            ++this.Bus.Address();
+            ++this.Bus.Address.Word;
             this.BusWrite(value.High);
         }
 

EightBit/Processor.cs

@@ -10,7 +10,6 @@ namespace EightBit
     {
         private PinLevel resetLine;
         private PinLevel intLine;
-        private Register16 pc;
 
         protected Processor(Bus memory)
         {
@@ -35,9 +34,9 @@ namespace EightBit
 
         public Bus Bus { get; }
 
-        protected byte OpCode { get; set; }
+        public Register16 PC { get; } = new Register16();
 
-        public ref Register16 PC() => ref this.pc;
+        protected byte OpCode { get; set; }
 
         public ref PinLevel RESET() => ref this.resetLine;
 
@@ -118,14 +117,14 @@ namespace EightBit
 
         protected void BusWrite(byte low, byte high, byte data)
         {
-            this.Bus.Address().Low = low;
-            this.Bus.Address().High = high;
+            this.Bus.Address.Low = low;
+            this.Bus.Address.High = high;
             this.BusWrite(data);
         }
 
         protected void BusWrite(ushort address, byte data)
         {
-            this.Bus.Address().Word = address;
+            this.Bus.Address.Word = address;
             this.BusWrite(data);
         }
 
@@ -141,14 +140,14 @@ namespace EightBit
 
         protected byte BusRead(byte low, byte high)
         {
-            this.Bus.Address().Low = low;
-            this.Bus.Address().High = high;
+            this.Bus.Address.Low = low;
+            this.Bus.Address.High = high;
             return this.BusRead();
         }
 
         protected byte BusRead(ushort address)
         {
-            this.Bus.Address().Word = address;
+            this.Bus.Address.Word = address;
             return this.BusRead();
         }
 
@@ -156,7 +155,7 @@ namespace EightBit
 
         protected virtual byte BusRead() => this.Bus.Read();   // N.B. Should be the only real call into the "Bus.Read" code.
 
-        protected byte FetchByte() => this.BusRead(this.PC()++);
+        protected byte FetchByte() => this.BusRead(this.PC.Word++);
 
         protected abstract Register16 GetWord();
 
@@ -178,23 +177,23 @@ namespace EightBit
 
         protected Register16 GetWord(ushort address)
         {
-            this.Bus.Address().Word = address;
+            this.Bus.Address.Word = address;
             return this.GetWord();
         }
 
         protected void SetWord(ushort address, Register16 value)
         {
-            this.Bus.Address().Word = address;
+            this.Bus.Address.Word = address;
             this.SetWord(value);
         }
 
-        protected void Jump(ushort destination) => this.PC().Word = destination;
+        protected void Jump(ushort destination) => this.PC.Word = destination;
 
         protected void Jump(Register16 destination) => this.Jump(destination.Word);
 
         protected void Call(ushort destination)
         {
-            this.PushWord(this.PC());
+            this.PushWord(this.PC);
             this.Jump(destination);
         }
 

EightBit/Ram.cs

@@ -6,11 +6,16 @@ namespace EightBit
 {
     public class Ram : Rom
     {
-        public Ram(int size = 0)
+        public Ram(int size)
         : base(size)
         {
         }
 
+        public Ram()
+        : this(0)
+        {
+        }
+
         public override sealed ref byte Reference(ushort address) => ref this.Bytes()[address];
 
         public new void Poke(ushort address, byte value) => base.Poke(address, value);

EightBit/Register16.cs

@@ -8,11 +8,8 @@ namespace EightBit
     using System.Runtime.InteropServices;
 
     [DebuggerDisplay("Word = {Word}")]
-    public struct Register16
+    public class Register16
     {
-        public byte Low;
-        public byte High;
-
         public Register16(byte low, byte high)
         {
             this.Low = low;
@@ -25,6 +22,11 @@ namespace EightBit
             this.High = Chip.HighByte(value);
         }
 
+        public Register16()
+        : this((ushort)0)
+        {
+        }
+
         public Register16(int value)
         : this((ushort)value)
         {
@@ -55,6 +57,10 @@ namespace EightBit
             }
         }
 
+        public byte Low { get; set; }
+
+        public byte High { get; set; }
+
         public static Register16 operator ++(Register16 value) => Increment(value);
 
         public static Register16 operator --(Register16 value) => Decrement(value);
@@ -77,12 +83,12 @@ namespace EightBit
 
         public override bool Equals(object obj)
         {
-            if (!(obj is Register16))
+            var rhs = obj as Register16;
+            if (rhs == null)
             {
                 return false;
             }
 
-            var rhs = (Register16)obj;
             return rhs.Low == this.Low && rhs.High == this.High;
         }