Added 16-bit register-to-register ADD handlers for r16, r/m16 and r/m16, r16 instructions

X86Disassembler/X86/Handlers/Add/AddR16Rm16Handler.cs

@@ -0,0 +1,72 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Add;
+
+/// <summary>
+/// Handler for ADD r16, r/m16 instruction (opcode 03 with 0x66 prefix)
+/// </summary>
+public class AddR16Rm16Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the AddR16Rm16Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public AddR16Rm16Handler(InstructionDecoder decoder)
+        : base(decoder)
+    {
+    }
+
+    /// <summary>
+    /// Checks if this handler can decode the given opcode
+    /// </summary>
+    /// <param name="opcode">The opcode to check</param>
+    /// <returns>True if this handler can decode the opcode</returns>
+    public override bool CanHandle(byte opcode)
+    {
+        // ADD r16, r/m16 is encoded as 0x03 with 0x66 prefix
+        if (opcode != 0x03)
+        {
+            return false;
+        }
+
+        // Only handle when the operand size prefix is present
+        return Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes an ADD r16, r/m16 instruction
+    /// </summary>
+    /// <param name="opcode">The opcode of the instruction</param>
+    /// <param name="instruction">The instruction object to populate</param>
+    /// <returns>True if the instruction was successfully decoded</returns>
+    public override bool Decode(byte opcode, Instruction instruction)
+    {
+        // Set the instruction type
+        instruction.Type = InstructionType.Add;
+
+        // Check if we can read the ModR/M byte
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // For ADD r16, r/m16 (0x03 with 0x66 prefix):
+        // - The reg field of the ModR/M byte specifies the destination register
+        // - The r/m field with mod specifies the source operand (register or memory)
+        var (_, reg, _, sourceOperand) = ModRMDecoder.ReadModRM16();
+
+        // Note: The operand size is already set to 16-bit by the ReadModRM16 method
+
+        // Create the destination register operand with 16-bit size
+        var destinationOperand = OperandFactory.CreateRegisterOperand(reg, 16);
+
+        // Set the structured operands
+        instruction.StructuredOperands = 
+        [
+            destinationOperand,
+            sourceOperand
+        ];
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/Add/AddRm16R16Handler.cs

@@ -0,0 +1,72 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Add;
+
+/// <summary>
+/// Handler for ADD r/m16, r16 instruction (opcode 01 with 0x66 prefix)
+/// </summary>
+public class AddRm16R16Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the AddRm16R16Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public AddRm16R16Handler(InstructionDecoder decoder)
+        : base(decoder)
+    {
+    }
+
+    /// <summary>
+    /// Checks if this handler can decode the given opcode
+    /// </summary>
+    /// <param name="opcode">The opcode to check</param>
+    /// <returns>True if this handler can decode the opcode</returns>
+    public override bool CanHandle(byte opcode)
+    {
+        // ADD r/m16, r16 is encoded as 0x01 with 0x66 prefix
+        if (opcode != 0x01)
+        {
+            return false;
+        }
+
+        // Only handle when the operand size prefix is present
+        return Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes an ADD r/m16, r16 instruction
+    /// </summary>
+    /// <param name="opcode">The opcode of the instruction</param>
+    /// <param name="instruction">The instruction object to populate</param>
+    /// <returns>True if the instruction was successfully decoded</returns>
+    public override bool Decode(byte opcode, Instruction instruction)
+    {
+        // Set the instruction type
+        instruction.Type = InstructionType.Add;
+
+        // Check if we can read the ModR/M byte
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // For ADD r/m16, r16 (0x01 with 0x66 prefix):
+        // - The reg field of the ModR/M byte specifies the source register
+        // - The r/m field with mod specifies the destination operand (register or memory)
+        var (_, reg, _, destinationOperand) = ModRMDecoder.ReadModRM16();
+
+        // Note: The operand size is already set to 16-bit by the ReadModRM16 method
+
+        // Create the source register operand with 16-bit size
+        var sourceOperand = OperandFactory.CreateRegisterOperand(reg, 16);
+
+        // Set the structured operands
+        instruction.StructuredOperands = 
+        [
+            destinationOperand,
+            sourceOperand
+        ];
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/InstructionHandlerFactory.cs

@@ -297,6 +297,10 @@ public class InstructionHandlerFactory
         _handlers.Add(new AddRm32R32Handler(_decoder));    // ADD r/m32, r32 (opcode 01)
         _handlers.Add(new AddEaxImmHandler(_decoder));     // ADD EAX, imm32 (opcode 05)
         
+        // Add ADD register-to-register handlers (16-bit)
+        _handlers.Add(new AddR16Rm16Handler(_decoder));    // ADD r16, r/m16 (opcode 03 with 0x66 prefix)
+        _handlers.Add(new AddRm16R16Handler(_decoder));    // ADD r/m16, r16 (opcode 01 with 0x66 prefix)
+        
         // Add ADD register-to-register handlers (8-bit)
         _handlers.Add(new AddRm8R8Handler(_decoder));      // ADD r/m8, r8 (opcode 00)
         _handlers.Add(new AddR8Rm8Handler(_decoder));      // ADD r8, r/m8 (opcode 02)

X86DisassemblerTests/TestData/add_tests.csv

@@ -31,6 +31,6 @@ RawBytes;Instructions
 810488AA000000;[{ "Type": "Add", "Operands": ["dword ptr [eax+ecx*4]", "0xAA"] }]
 
 # Mixed addressing modes
-00A314285600;[{ "Type": "Add", "Operands": ["byte ptr [ebx+0x562814]", "ah"] }]
-6601B310203040;[{ "Type": "Add", "Operands": ["si", "word ptr [ebx+0x40302010]"] }]
-030C8D10203040;[{ "Type": "Add", "Operands": ["ecx", "dword ptr [ebp*4+0x40302010]"] }]
+00A314285600;[{ "Type": "Add", "Operands": ["byte ptr [ebx+0x00562814]", "ah"] }]
+6601B310203040;[{ "Type": "Add", "Operands": ["word ptr [ebx+0x40302010]", "si"] }]
+030C8D10203040;[{ "Type": "Add", "Operands": ["ecx", "dword ptr [ecx*4+0x40302010]"] }]