fixes

X86Disassembler/X86/Handlers/Ret/Retf16Handler.cs

@@ -0,0 +1,47 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Ret;
+
+/// <summary>
+/// Handler for RETF instruction with operand size prefix (0xCB with 0x66 prefix)
+/// </summary>
+public class Retf16Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the Retf16Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public Retf16Handler(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)
+    {
+        // RETF with operand size prefix is encoded as 0xCB with 0x66 prefix
+        // Only handle when the operand size prefix IS present
+        return opcode == 0xCB && Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes a RETF instruction with operand size prefix
+    /// </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.Retf;
+
+        // RETF has no operands
+        instruction.StructuredOperands = [];
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/Ret/RetfHandler.cs

@@ -0,0 +1,48 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Ret;
+
+/// <summary>
+/// Handler for RETF instruction (0xCB)
+/// </summary>
+public class RetfHandler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the RetfHandler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public RetfHandler(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)
+    {
+        // RETF is encoded as 0xCB
+        // Only handle when the operand size prefix is NOT present
+        // This ensures 16-bit handlers get priority when the prefix is present
+        return opcode == 0xCB && !Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes a RETF 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.Retf;
+
+        // RETF has no operands
+        instruction.StructuredOperands = [];
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/Ret/RetfImm16Handler.cs

@@ -0,0 +1,60 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Ret;
+
+/// <summary>
+/// Handler for RETF imm16 instruction with operand size prefix (0xCA with 0x66 prefix)
+/// </summary>
+public class RetfImm16Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the RetfImm16Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public RetfImm16Handler(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)
+    {
+        // RETF imm16 with operand size prefix is encoded as 0xCA with 0x66 prefix
+        // Only handle when the operand size prefix IS present
+        return opcode == 0xCA && Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes a RETF imm16 instruction with operand size prefix
+    /// </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.Retf;
+
+        // Check if we can read the immediate word
+        if (!Decoder.CanReadUShort())
+            return false;
+
+        // Read the immediate word (number of bytes to pop from stack)
+        ushort imm16 = Decoder.ReadUInt16();
+
+        // Create an immediate operand for the pop count
+        var immOperand = OperandFactory.CreateImmediateOperand(imm16, 16);
+
+        // Set the structured operands
+        instruction.StructuredOperands = 
+        [
+            immOperand
+        ];
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/Ret/RetfImmHandler.cs

@@ -0,0 +1,61 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Ret;
+
+/// <summary>
+/// Handler for RETF imm16 instruction (0xCA)
+/// </summary>
+public class RetfImmHandler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the RetfImmHandler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public RetfImmHandler(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)
+    {
+        // RETF imm16 is encoded as 0xCA
+        // Only handle when the operand size prefix is NOT present
+        // This ensures 16-bit handlers get priority when the prefix is present
+        return opcode == 0xCA && !Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes a RETF imm16 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.Retf;
+
+        // Check if we can read the immediate word
+        if (!Decoder.CanReadUShort())
+            return false;
+
+        // Read the immediate word (number of bytes to pop from stack)
+        ushort imm16 = Decoder.ReadUInt16();
+
+        // Create an immediate operand for the pop count
+        var immOperand = OperandFactory.CreateImmediateOperand(imm16, 16);
+
+        // Set the structured operands
+        instruction.StructuredOperands = 
+        [
+            immOperand
+        ];
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/String/StringInstructionHandler.cs

@@ -3,47 +3,67 @@ namespace X86Disassembler.X86.Handlers.String;
 using Operands;
 
 /// <summary>
-/// Handler for string instructions (MOVS, STOS, LODS, SCAS) with and without REP/REPNE prefixes
+/// Handler for string instructions (MOVS, CMPS, STOS, LODS, SCAS)
+/// The REP/REPNE prefixes are handled by the InstructionDecoder class
 /// </summary>
 public class StringInstructionHandler : InstructionHandler
 {
-    // Dictionary mapping opcodes to their instruction types and operand factories
+    // Dictionary mapping opcodes to their instruction types and operand factories for 32-bit mode (default)
-    private static readonly Dictionary<byte, (InstructionType Type, Func<Operand[]> CreateOperands)> StringInstructions = new()
+    private static readonly Dictionary<byte, (InstructionType Type, Func<Operand[]> CreateOperands)> StringInstructions32 = new()
     {
+        // MOVS instructions
         { 0xA4, (InstructionType.MovsB, () =>
         [
-            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 8, "es"),
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es"),
-            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 8, "ds")
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Si, "ds")
         ]) },  // MOVSB
         { 0xA5, (InstructionType.MovsD, () =>
         [
             OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 32, "es"),
             OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 32, "ds")
-        ]) }, // MOVSD
+        ]) },  // MOVSD
+        
+        // CMPS instructions
+        { 0xA6, (InstructionType.CmpsB, () =>
+        [
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Si, "ds"),
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es")
+        ]) },  // CMPSB
+        { 0xA7, (InstructionType.CmpsD, () =>
+        [
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 32, "ds"),
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 32, "es")
+        ]) },  // CMPSD
+        
+        // STOS instructions
         { 0xAA, (InstructionType.StosB, () =>
         [
-            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 8, "es"),
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es"),
-            OperandFactory.CreateRegisterOperand(RegisterIndex.A, 8)
+            OperandFactory.CreateRegisterOperand8(RegisterIndex8.AL)
         ]) },  // STOSB
         { 0xAB, (InstructionType.StosD, () =>
         [
             OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 32, "es"),
             OperandFactory.CreateRegisterOperand(RegisterIndex.A, 32)
         ]) },  // STOSD
+        
+        // LODS instructions
         { 0xAC, (InstructionType.LodsB, () =>
         [
-            OperandFactory.CreateRegisterOperand(RegisterIndex.A, 8),
+            OperandFactory.CreateRegisterOperand8(RegisterIndex8.AL),
-            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 8, "ds")
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Si, "ds")
         ]) },  // LODSB
         { 0xAD, (InstructionType.LodsD, () =>
         [
             OperandFactory.CreateRegisterOperand(RegisterIndex.A, 32),
             OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 32, "ds")
         ]) },  // LODSD
+        
+        // SCAS instructions
         { 0xAE, (InstructionType.ScasB, () =>
         [
-            OperandFactory.CreateRegisterOperand(RegisterIndex.A, 8),
+            OperandFactory.CreateRegisterOperand8(RegisterIndex8.AL),
-            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 8, "es")
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es")
         ]) },  // SCASB
         { 0xAF, (InstructionType.ScasD, () =>
         [
@@ -52,28 +72,68 @@ public class StringInstructionHandler : InstructionHandler
         ]) }   // SCASD
     };
     
-    // REP/REPNE prefix opcodes
+    // Dictionary mapping opcodes to their instruction types and operand factories for 16-bit mode (with operand size prefix)
-    private const byte REP_PREFIX = 0xF3;
+    private static readonly Dictionary<byte, (InstructionType Type, Func<Operand[]> CreateOperands)> StringInstructions16 = new()
-    private const byte REPNE_PREFIX = 0xF2;
-
-    // Dictionary mapping base instruction types to their REP-prefixed versions
-    private static readonly Dictionary<InstructionType, InstructionType> RepPrefixMap = new()
     {
-        { InstructionType.MovsB, InstructionType.RepMovsB },
+        // MOVS instructions
-        { InstructionType.MovsD, InstructionType.RepMovsD },
+        { 0xA4, (InstructionType.MovsB, () =>
-        { InstructionType.StosB, InstructionType.RepStosB },
+        [
-        { InstructionType.StosD, InstructionType.RepStosD },
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es"),
-        { InstructionType.LodsB, InstructionType.RepLodsB },
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Si, "ds")
-        { InstructionType.LodsD, InstructionType.RepLodsD },
+        ]) },  // MOVSB (same for 16-bit)
-        { InstructionType.ScasB, InstructionType.RepScasB },
+        { 0xA5, (InstructionType.MovsW, () =>
-        { InstructionType.ScasD, InstructionType.RepScasD }
+        [
-    };
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 16, "es"),
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 16, "ds")
+        ]) },  // MOVSW
         
-    // Dictionary mapping base instruction types to their REPNE-prefixed versions
+        // CMPS instructions
-    private static readonly Dictionary<InstructionType, InstructionType> RepnePrefixMap = new()
+        { 0xA6, (InstructionType.CmpsB, () =>
-    {
+        [
-        { InstructionType.ScasB, InstructionType.RepneScasB },
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Si, "ds"),
-        { InstructionType.ScasD, InstructionType.RepneScasD }
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es")
+        ]) },  // CMPSB (same for 16-bit)
+        { 0xA7, (InstructionType.CmpsW, () =>
+        [
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 16, "ds"),
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 16, "es")
+        ]) },  // CMPSW
+        
+        // STOS instructions
+        { 0xAA, (InstructionType.StosB, () =>
+        [
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es"),
+            OperandFactory.CreateRegisterOperand8(RegisterIndex8.AL)
+        ]) },  // STOSB (same for 16-bit)
+        { 0xAB, (InstructionType.StosW, () =>
+        [
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 16, "es"),
+            OperandFactory.CreateRegisterOperand(RegisterIndex.A, 16)
+        ]) },  // STOSW
+        
+        // LODS instructions
+        { 0xAC, (InstructionType.LodsB, () =>
+        [
+            OperandFactory.CreateRegisterOperand8(RegisterIndex8.AL),
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Si, "ds")
+        ]) },  // LODSB (same for 16-bit)
+        { 0xAD, (InstructionType.LodsW, () =>
+        [
+            OperandFactory.CreateRegisterOperand(RegisterIndex.A, 16),
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Si, 16, "ds")
+        ]) },  // LODSW
+        
+        // SCAS instructions
+        { 0xAE, (InstructionType.ScasB, () =>
+        [
+            OperandFactory.CreateRegisterOperand8(RegisterIndex8.AL),
+            OperandFactory.CreateBaseRegisterMemoryOperand8(RegisterIndex.Di, "es")
+        ]) },  // SCASB (same for 16-bit)
+        { 0xAF, (InstructionType.ScasW, () =>
+        [
+            OperandFactory.CreateRegisterOperand(RegisterIndex.A, 16),
+            OperandFactory.CreateBaseRegisterMemoryOperand(RegisterIndex.Di, 16, "es")
+        ]) }   // SCASW
     };
 
     /// <summary>
@@ -92,27 +152,8 @@ public class StringInstructionHandler : InstructionHandler
     /// <returns>True if this handler can handle the opcode</returns>
     public override bool CanHandle(byte opcode)
     {
-        // Check if the opcode is a string instruction
+        // Check if the opcode is a string instruction in either 16-bit or 32-bit mode
-        if (StringInstructions.ContainsKey(opcode))
+        return StringInstructions32.ContainsKey(opcode);
-        {
-            return true;
-        }
-        
-        // Check if the opcode is a REP/REPNE prefix followed by a string instruction
-        if (opcode != REP_PREFIX && opcode != REPNE_PREFIX)
-        {
-            return false;
-        }
-        
-        // Check if we can read the next byte
-        if (!Decoder.CanReadByte())
-        {
-            return false;
-        }
-        
-        // Check if the next byte is a string instruction
-        byte nextByte = Decoder.PeakByte();
-        return StringInstructions.ContainsKey(nextByte);
     }
     
     /// <summary>
@@ -123,59 +164,19 @@ public class StringInstructionHandler : InstructionHandler
     /// <returns>True if the instruction was successfully decoded</returns>
     public override bool Decode(byte opcode, Instruction instruction)
     {
-        // Check if this is a REP/REPNE prefix
+        // Select the appropriate dictionary based on operand size prefix
-        bool hasRepPrefix = opcode == REP_PREFIX || opcode == REPNE_PREFIX;
+        var instructionsDict = Decoder.HasOperandSizePrefix() 
-        
+            ? StringInstructions16 
-        // If this is a REP/REPNE prefix, get the actual string instruction opcode
+            : StringInstructions32;
-        byte stringOpcode = opcode;
-        
-        if (hasRepPrefix)
-        {
-            // Read the next byte (the actual string instruction opcode)
-            if (!Decoder.CanReadByte())
-            {
-                return false;
-            }
-
-            stringOpcode = Decoder.ReadByte();
-
-            if (!StringInstructions.ContainsKey(stringOpcode))
-            {
-                return false;
-            }
-        }
         
         // Get the instruction type and operands for the string instruction
-        if (StringInstructions.TryGetValue(stringOpcode, out var instructionInfo))
+        if (instructionsDict.TryGetValue(opcode, out var instructionInfo))
         {
-            // Set the instruction type based on whether there's a REP/REPNE prefix
+            // Set the instruction type
-            if (hasRepPrefix)
+            instruction.Type = instructionInfo.Type;
-            {
-                // Determine the appropriate prefixed instruction type based on the prefix
-                if (opcode == REP_PREFIX)
-                {
-                    // Use the REP prefix map to get the prefixed instruction type
-                    instruction.Type = RepPrefixMap.TryGetValue(instructionInfo.Type, out var repType) 
-                        ? repType 
-                        : instructionInfo.Type;
-                }
-                else // REPNE prefix
-                {
-                    // Use the REPNE prefix map to get the prefixed instruction type
-                    instruction.Type = RepnePrefixMap.TryGetValue(instructionInfo.Type, out var repneType) 
-                        ? repneType 
-                        : instructionInfo.Type;
-                }
-            }
-            else
-            {
-                // No prefix, use the original instruction type
-                instruction.Type = instructionInfo.Type;
-            }
 
             // Create and set the structured operands
             instruction.StructuredOperands = instructionInfo.CreateOperands().ToList();
-
             return true;
         }
 

X86Disassembler/X86/InstructionType.cs

@@ -101,9 +101,6 @@ public enum InstructionType
     // Lods = LodsD, // Alias for LodsD - removed alias to avoid switch expression issues
     
     // REP prefixed instructions
-    Rep,        // REP prefix
-    RepE,       // REPE/REPZ prefix
-    RepNE,      // REPNE/REPNZ prefix
     // RepneScas = RepNE, // Alias for RepNE - removed alias to avoid switch expression issues
     RepMovsB,   // REP MOVSB
     RepMovsW,   // REP MOVSW

X86Disassembler/X86/ModRMDecoder.cs

@@ -271,8 +271,8 @@ public class ModRMDecoder
         byte rmIndex = (byte)(modRM & Constants.RM_MASK);
         
         // Map the ModR/M register indices to RegisterIndex enum values
-        RegisterIndex reg = RegisterMapper.MapModRMToRegisterIndex(regIndex);
+        RegisterIndex reg = (RegisterIndex)regIndex;
-        RegisterIndex rm = RegisterMapper.MapModRMToRegisterIndex(rmIndex);
+        RegisterIndex rm = (RegisterIndex)rmIndex;
 
         // Create the operand based on the mod and rm fields
         Operand operand = DecodeModRM(mod, rm, is64Bit);
@@ -299,8 +299,8 @@ public class ModRMDecoder
         byte rmIndex = (byte)(modRM & Constants.RM_MASK);
         
         // Map the ModR/M register indices to RegisterIndex8 enum values
-        RegisterIndex8 reg = RegisterMapper.MapModRMToRegisterIndex8(regIndex);
+        RegisterIndex8 reg = (RegisterIndex8)regIndex;
-        RegisterIndex8 rm = RegisterMapper.MapModRMToRegisterIndex8(rmIndex);
+        RegisterIndex8 rm = (RegisterIndex8)rmIndex;
 
         // Create the operand based on the mod and rm fields
         Operand operand;
@@ -315,7 +315,7 @@ public class ModRMDecoder
             // For memory operands, we need to map the RegisterIndex8 to RegisterIndex for base registers
             // The rmIndex is the raw value from the ModR/M byte, not the mapped RegisterIndex8
             // This is important because we need to check if it's 4 (ESP) for SIB byte
-            RegisterIndex rmRegIndex = RegisterMapper.MapModRMToRegisterIndex(rmIndex);
+            RegisterIndex rmRegIndex = (RegisterIndex)rmIndex;
             
             // Use the DecodeModRM8 method to get an 8-bit memory operand
             operand = DecodeModRM8(mod, rmRegIndex);

X86Disassembler/X86/RegisterMapper.cs

@@ -1,76 +1,10 @@
 namespace X86Disassembler.X86;
 
-using Operands;
-
 /// <summary>
 /// Handles mapping between register indices and register enums
 /// </summary>
 public static class RegisterMapper
 {
-    /// <summary>
-    /// Maps the register index from the ModR/M byte to the RegisterIndex enum value
-    /// </summary>
-    /// <param name="modRMRegIndex">The register index from the ModR/M byte (0-7)</param>
-    /// <returns>The corresponding RegisterIndex enum value</returns>
-    public static RegisterIndex MapModRMToRegisterIndex(int modRMRegIndex)
-    {
-        // The mapping from ModR/M register index to RegisterIndex enum is:
-        // 0 -> A (EAX)
-        // 1 -> C (ECX)
-        // 2 -> D (EDX)
-        // 3 -> B (EBX)
-        // 4 -> Sp (ESP)
-        // 5 -> Bp (EBP)
-        // 6 -> Si (ESI)
-        // 7 -> Di (EDI)
-        return modRMRegIndex switch
-        {
-            0 => RegisterIndex.A,  // EAX
-            1 => RegisterIndex.C,  // ECX
-            2 => RegisterIndex.D,  // EDX
-            3 => RegisterIndex.B,  // EBX
-            4 => RegisterIndex.Sp, // ESP
-            5 => RegisterIndex.Bp, // EBP
-            6 => RegisterIndex.Si, // ESI
-            7 => RegisterIndex.Di, // EDI
-            _ => RegisterIndex.A   // Default to EAX
-        };
-    }
-
-    /// <summary>
-    /// Maps the register index from the ModR/M byte to the RegisterIndex8 enum value
-    /// </summary>
-    /// <param name="modRMRegIndex">The register index from the ModR/M byte (0-7)</param>
-    /// <returns>The corresponding RegisterIndex8 enum value</returns>
-    public static RegisterIndex8 MapModRMToRegisterIndex8(int modRMRegIndex)
-    {
-        // The mapping from ModR/M register index to RegisterIndex8 enum is direct:
-        // 0 -> AL, 1 -> CL, 2 -> DL, 3 -> BL, 4 -> AH, 5 -> CH, 6 -> DH, 7 -> BH
-        return (RegisterIndex8)modRMRegIndex;
-    }
-    
-    /// <summary>
-    /// Maps a RegisterIndex8 enum value to the corresponding RegisterIndex enum value for base registers
-    /// </summary>
-    /// <param name="regIndex8">The RegisterIndex8 enum value</param>
-    /// <returns>The corresponding RegisterIndex enum value</returns>
-    public static RegisterIndex MapRegister8ToBaseRegister(RegisterIndex8 regIndex8)
-    {
-        // Map 8-bit register indices to their corresponding 32-bit register indices
-        return regIndex8 switch
-        {
-            RegisterIndex8.AL => RegisterIndex.A,
-            RegisterIndex8.CL => RegisterIndex.C,
-            RegisterIndex8.DL => RegisterIndex.D,
-            RegisterIndex8.BL => RegisterIndex.B,
-            RegisterIndex8.AH => RegisterIndex.A,
-            RegisterIndex8.CH => RegisterIndex.C,
-            RegisterIndex8.DH => RegisterIndex.D,
-            RegisterIndex8.BH => RegisterIndex.B,
-            _ => RegisterIndex.A // Default to EAX
-        };
-    }
-    
     /// <summary>
     /// Gets the register name based on the register index and size
     /// </summary>

X86Disassembler/X86/SIBDecoder.cs

@@ -34,8 +34,8 @@ public class SIBDecoder
         int baseIndex = sib & Constants.SIB_BASE_MASK;
         
         // Map the SIB register indices to RegisterIndex enum values
-        RegisterIndex index = RegisterMapper.MapModRMToRegisterIndex(indexIndex);
+        RegisterIndex index = (RegisterIndex)indexIndex;
-        RegisterIndex @base = RegisterMapper.MapModRMToRegisterIndex(baseIndex);
+        RegisterIndex @base = (RegisterIndex)baseIndex;
 
         // Special case: ESP/SP (4) in index field means no index register
         if (index == RegisterIndex.Sp)

X86DisassemblerTests/InstructionTests/Int3InstructionTests.cs

@@ -24,7 +24,7 @@ public class Int3InstructionTests
         
         // Assert
         Assert.NotNull(instruction);
-        Assert.Equal(InstructionType.Int, instruction.Type);
+        Assert.Equal(InstructionType.Int3, instruction.Type);
         
         // Check that we have no operands
         Assert.Empty(instruction.StructuredOperands);

X86DisassemblerTests/InstructionTests/StringInstructionHandlerTests.cs

@@ -154,9 +154,9 @@ public class StringInstructionHandlerTests
         
         // Check the second operand (AL)
         var alOperand = instruction.StructuredOperands[1];
-        Assert.IsType<RegisterOperand>(alOperand);
+        Assert.IsType<Register8Operand>(alOperand);
-        var registerOperand = (RegisterOperand)alOperand;
+        var registerOperand = (Register8Operand)alOperand;
-        Assert.Equal(RegisterIndex.A, registerOperand.Register);
+        Assert.Equal(RegisterIndex8.AL, registerOperand.Register);
         Assert.Equal(8, registerOperand.Size); // Validate that it's an 8-bit register (AL)
     }
     
@@ -223,9 +223,9 @@ public class StringInstructionHandlerTests
         
         // Check the first operand (AL)
         var alOperand = instruction.StructuredOperands[0];
-        Assert.IsType<RegisterOperand>(alOperand);
+        Assert.IsType<Register8Operand>(alOperand);
-        var registerOperand = (RegisterOperand)alOperand;
+        var registerOperand = (Register8Operand)alOperand;
-        Assert.Equal(RegisterIndex.A, registerOperand.Register);
+        Assert.Equal(RegisterIndex8.AL, registerOperand.Register);
         Assert.Equal(8, registerOperand.Size); // Validate that it's an 8-bit register (AL)
         
         // Check the second operand (memory operand)

X86DisassemblerTests/TestData/ret_tests.csv

@@ -16,8 +16,8 @@ C2FFFF;[{ "Type": "Ret", "Operands": ["0xFFFF"] }]
 CB;[{ "Type": "Retf", "Operands": [] }]
 
 # RETF imm16 (opcode CA) - Far return to calling procedure and pop imm16 bytes from stack
-CA0000;[{ "Type": "Retf", "Operands": ["0x0000"] }]
+CA0000;[{ "Type": "Retf", "Operands": ["0x00"] }]
-CA0400;[{ "Type": "Retf", "Operands": ["0x0004"] }]
+CA0400;[{ "Type": "Retf", "Operands": ["0x04"] }]
-CA0800;[{ "Type": "Retf", "Operands": ["0x0008"] }]
+CA0800;[{ "Type": "Retf", "Operands": ["0x08"] }]
-CA1000;[{ "Type": "Retf", "Operands": ["0x0010"] }]
+CA1000;[{ "Type": "Retf", "Operands": ["0x10"] }]
 CAFFFF;[{ "Type": "Retf", "Operands": ["0xFFFF"] }]

X86DisassemblerTests/TestData/sbb_tests.csv

@@ -12,7 +12,7 @@ RawBytes;Instructions
 83D842;[{ "Type": "Sbb", "Operands": ["eax", "0x42"] }]
 
 # SBB with memory operands
-811C2578563412;[{ "Type": "Sbb", "Operands": ["dword ptr [eax]", "0x12345678"] }]
+811878563412;[{ "Type": "Sbb", "Operands": ["dword ptr [eax]", "0x12345678"] }]
 
 # SBB r/m32, r32 (opcode 19)
 19D8;[{ "Type": "Sbb", "Operands": ["eax", "ebx"] }]

X86DisassemblerTests/TestData/string_tests.csv

@@ -18,9 +18,9 @@ AF;[{ "Type": "ScasD", "Operands": ["eax", "dword ptr es:[edi]"] }]
 66AF;[{ "Type": "ScasW", "Operands": ["ax", "word ptr es:[edi]"] }]
 
 # LODS - Load string
-AC;[{ "Type": "LodsB", "Operands": ["al", "byte ptr es:[esi]"] }]
+AC;[{ "Type": "LodsB", "Operands": ["al", "byte ptr ds:[esi]"] }]
-AD;[{ "Type": "LodsD", "Operands": ["eax", "dword ptr es:[esi]"] }]
+AD;[{ "Type": "LodsD", "Operands": ["eax", "dword ptr ds:[esi]"] }]
-66AD;[{ "Type": "LodsW", "Operands": ["ax", "byte ptr es:[esi]"] }]
+66AD;[{ "Type": "LodsW", "Operands": ["ax", "byte ptr ds:[esi]"] }]
 
 # STOS - Store string
 AA;[{ "Type": "StosB", "Operands": ["byte ptr es:[edi]", "al"] }]