mirrors/ParkanPlayground
0
Fork 0
mirror of https://github.com/sampletext32/ParkanPlayground.git synced 2025-06-20 16:18:37 +03:00
Code Issues Releases Activity

Fixed floating point comparison handlers for FCOM ST(i) and FCOMP ST(i) instructions

Browse Source
This commit is contained in:
bird_egop
2025-04-18 01:25:34 +03:00
parent 84d5652a62
commit 2a8cf9534e
6 changed files with 47 additions and 57 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
X86Disassembler/X86/Handlers/FloatingPoint/Comparison/FcompStHandler.cs
View File

@ -3,7 +3,7 @@ namespace X86Disassembler.X86.Handlers.FloatingPoint.Comparison;
using X86Disassembler.X86.Operands;
/// <summary>
/// Handler for FCOMP ST(0) instruction (DE D3)
/// Handler for FCOMP ST(i) instruction (D8 D8-DF) - compares ST(0) with ST(i) and pops the register stack
/// </summary>
public class FcompStHandler : InstructionHandler
{
@ -23,21 +23,25 @@ public class FcompStHandler : InstructionHandler
/// <returns>True if this handler can decode the opcode</returns>
public override bool CanHandle(byte opcode)
{
// FCOMP ST(0) is DE D3
if (opcode != 0xDE) return false;
// FCOMP ST(i) is D8 D8-DF (compares ST(0) with ST(i) and pops the register stack)
if (opcode != 0xD8) return false;
if (!Decoder.CanReadByte())
{
return false;
}
// Check if the ModR/M byte is exactly D3 (reg = 2, rm = 3, mod = 3)
byte modRm = Decoder.PeakByte();
return modRm == 0xD3;
var opcodeSecond = Decoder.PeakByte();
// this is a special case of a handler, only handling FCOMP with ST(i)
if (opcodeSecond < 0xD8 || opcodeSecond > 0xDF)
return false;
return true;
}
/// <summary>
/// Decodes a FCOMP ST(0) instruction
/// Decodes a FCOMP ST(i) instruction - compares ST(0) with ST(i) and pops the register stack
/// </summary>
/// <param name="opcode">The opcode of the instruction</param>
/// <param name="instruction">The instruction object to populate</param>
@ -48,20 +52,19 @@ public class FcompStHandler : InstructionHandler
{
return false;
}
// Read the ModR/M byte
var (mod, reg, rm, _) = ModRMDecoder.ReadModRM();
var stIndex = (FpuRegisterIndex)(Decoder.ReadByte() - 0xD8);
// Set the instruction type
instruction.Type = InstructionType.Fcomp;
// Create the FPU register operand
var fpuRegisterOperand = OperandFactory.CreateFPURegisterOperand(FpuRegisterIndex.ST0);
// Create the FPU register operands
var stiOperand = OperandFactory.CreateFPURegisterOperand(stIndex);
// Set the structured operands
instruction.StructuredOperands =
[
fpuRegisterOperand
stiOperand // The instruction is FCOMP ST(i), which compares ST(0) with ST(i) and pops the register stack
];
return true;