float handlers

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

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+namespace X86Disassembler.X86.Handlers.FloatingPoint.Arithmetic;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FSUBR ST, ST(i) instruction (D8 E8-EF)
+/// </summary>
+public class FsubrStStiHandler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FsubrStStHandler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FsubrStStiHandler(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 ST, ST(i) is D8 E8-EF
+        if (opcode != 0xD8) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check second opcode byte
+        byte secondOpcode = Decoder.PeakByte();
+        
+        // Only handle E8-EF
+        return secondOpcode is >= 0xE8 and <= 0xEF;
+    }
+    
+    /// <summary>
+    /// Decodes a FSUBR ST, ST(i) 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 and calculate ST(i) index
+        var stIndex = (FpuRegisterIndex)(Decoder.ReadByte() - 0xE8);
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fsubr;
+        
+        // Create the FPU register operands
+        var st0Operand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0);
+        var stiOperand = OperandFactory.CreateFPURegisterOperand(stIndex);
+        
+        // Set the structured operands
+        instruction.StructuredOperands = 
+        [
+            st0Operand,
+            stiOperand
+        ];
+
+        return true;
+    }
+}