Reorganize floating point handlers into logical subfolders

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FaddFloat32Handler.cs

@@ -0,0 +1,91 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FADD float32 instruction (D8 /0)
+/// </summary>
+public class FaddFloat32Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FaddFloat32Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FaddFloat32Handler(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)
+    {
+        // FADD is D8 /0
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 0
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 0;
+    }
+    
+    /// <summary>
+    /// Decodes a FADD float32 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+
+        // Verify reg field is 0 (FADD)
+        if (reg != 0)
+        {
+            return false;
+        }
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fadd;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For register operands, we need to handle the stack registers
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                st0Operand,
+                stiOperand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FaddFloat64Handler.cs

@@ -0,0 +1,91 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FADD float64 instruction (DC /0)
+/// </summary>
+public class FaddFloat64Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FaddFloat64Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FaddFloat64Handler(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)
+    {
+        // FADD is DC /0
+        if (opcode != 0xDC) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 0
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 0;
+    }
+    
+    /// <summary>
+    /// Decodes a FADD float64 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+
+        // Verify reg field is 0 (FADD)
+        if (reg != 0)
+        {
+            return false;
+        }
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fadd;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM64
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For DC C0-DC FF, the operands are reversed: ST(i), ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                stiOperand,
+                st0Operand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FdivFloat32Handler.cs

@@ -0,0 +1,85 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+/// <summary>
+/// Handler for FDIV float32 instruction (D8 /6)
+/// </summary>
+public class FdivFloat32Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FdivFloat32Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FdivFloat32Handler(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)
+    {
+        // FDIV is D8 /6
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 6
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 6;
+    }
+    
+    /// <summary>
+    /// Decodes a FDIV float32 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fdiv;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For register operands, we need to handle the stack registers
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                st0Operand,
+                stiOperand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FdivFloat64Handler.cs

@@ -0,0 +1,85 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FDIV float64 instruction (DC /6)
+/// </summary>
+public class FdivFloat64Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FdivFloat64Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FdivFloat64Handler(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)
+    {
+        // FDIV is DC /6
+        if (opcode != 0xDC) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 6
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 6;
+    }
+    
+    /// <summary>
+    /// Decodes a FDIV float64 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fdiv;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For DC F0-DC F7, the operands are reversed: ST(i), ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                stiOperand,
+                st0Operand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FdivrFloat32Handler.cs

@@ -0,0 +1,85 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+/// <summary>
+/// Handler for FDIVR float32 instruction (D8 /7)
+/// </summary>
+public class FdivrFloat32Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FdivrFloat32Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FdivrFloat32Handler(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)
+    {
+        // FDIVR is D8 /7
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 7
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 7;
+    }
+    
+    /// <summary>
+    /// Decodes a FDIVR float32 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fdivr;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For register operands, we need to handle the stack registers
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                st0Operand,
+                stiOperand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FdivrFloat64Handler.cs

@@ -0,0 +1,85 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FDIVR float64 instruction (DC /7)
+/// </summary>
+public class FdivrFloat64Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FdivrFloat64Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FdivrFloat64Handler(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)
+    {
+        // FDIVR is DC /7
+        if (opcode != 0xDC) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 7
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 7;
+    }
+    
+    /// <summary>
+    /// Decodes a FDIVR float64 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fdivr;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For DC F8-DC FF, the operands are reversed: ST(i), ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                stiOperand,
+                st0Operand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FmulFloat32Handler.cs

@@ -0,0 +1,87 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+/// <summary>
+/// Handler for FMUL float32 instruction (D8 /1)
+/// </summary>
+public class FmulFloat32Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FmulFloat32Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FmulFloat32Handler(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)
+    {
+        // FMUL is D8 /1
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 1
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 1;
+    }
+    
+    /// <summary>
+    /// Decodes a FMUL float32 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fmul;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For register operands, we need to handle the stack registers
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                st0Operand,
+                stiOperand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FmulFloat64Handler.cs

@@ -0,0 +1,85 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+/// <summary>
+/// Handler for FMUL float64 instruction (DC /1)
+/// </summary>
+public class FmulFloat64Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FmulFloat64Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FmulFloat64Handler(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)
+    {
+        // FMUL is DC /1
+        if (opcode != 0xDC) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 1
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 1;
+    }
+    
+    /// <summary>
+    /// Decodes a FMUL float64 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fmul;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM64
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For DC C0-DC FF, the operands are reversed: ST(i), ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                stiOperand,
+                st0Operand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FsubFloat32Handler.cs

@@ -0,0 +1,85 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+/// <summary>
+/// Handler for FSUB float32 instruction (D8 /4)
+/// </summary>
+public class FsubFloat32Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FsubFloat32Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FsubFloat32Handler(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)
+    {
+        // FSUB is D8 /4
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 4
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 4;
+    }
+    
+    /// <summary>
+    /// Decodes a FSUB float32 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fsub;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For register operands, we need to handle the stack registers
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                st0Operand,
+                stiOperand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FsubFloat64Handler.cs

@@ -0,0 +1,85 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FSUB float64 instruction (DC /4)
+/// </summary>
+public class FsubFloat64Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FsubFloat64Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FsubFloat64Handler(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)
+    {
+        // FSUB is DC /4
+        if (opcode != 0xDC) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 4
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 4;
+    }
+    
+    /// <summary>
+    /// Decodes a FSUB float64 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fsub;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For DC E0-DC E7, the operands are reversed: ST(i), ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                stiOperand,
+                st0Operand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FsubrFloat32Handler.cs

@@ -0,0 +1,85 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+/// <summary>
+/// Handler for FSUBR float32 instruction (D8 /5)
+/// </summary>
+public class FsubrFloat32Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FsubrFloat32Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FsubrFloat32Handler(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)
+    {
+        // FSUBR is D8 /5
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 5
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 5;
+    }
+    
+    /// <summary>
+    /// Decodes a FSUBR float32 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fsubr;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For register operands, we need to handle the stack registers
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                st0Operand,
+                stiOperand
+            ];
+        }
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/FloatingPoint/Arithmetic/FsubrFloat64Handler.cs

@@ -0,0 +1,85 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FSUBR float64 instruction (DC /5)
+/// </summary>
+public class FsubrFloat64Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FsubrFloat64Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FsubrFloat64Handler(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)
+    {
+        // FSUBR is DC /5
+        if (opcode != 0xDC) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the ModR/M byte has reg field = 5
+        byte modRm = Decoder.PeakByte();
+        byte reg = (byte)((modRm >> 3) & 0x7);
+        
+        return reg == 5;
+    }
+    
+    /// <summary>
+    /// Decodes a FSUBR float64 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte using the specialized FPU method
+        var (mod, reg, fpuRm, rawOperand) = ModRMDecoder.ReadModRMFpu();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fsubr;
+
+        // For memory operands, set the operand
+        if (mod != 3) // Memory operand
+        {
+            // Set the structured operands - the operand already has the correct size from ReadModRM
+            instruction.StructuredOperands = 
+            [
+                rawOperand
+            ];
+        }
+        else // Register operand (ST(i))
+        {
+            // For DC E8-DC EF, the operands are reversed: ST(i), ST(0)
+            var stiOperand = OperandFactory.CreateFPURegisterOperand(fpuRm); // ST(i)
+            var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0); // ST(0)
+            
+            // Set the structured operands
+            instruction.StructuredOperands = 
+            [
+                stiOperand,
+                st0Operand
+            ];
+        }
+
+        return true;
+    }
+}