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Code Issues Releases Activity

Add support for FNSTSW instruction

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bird_egop
2025-04-12 19:21:32 +03:00
parent dffc405c10
commit ae1c4730d0
1 changed files with 36 additions and 0 deletions
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36
X86Disassembler/X86/Handlers/FloatingPointHandler.cs
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@ -8,12 +8,16 @@ public class FloatingPointHandler : InstructionHandler
// Floating-point instruction mnemonics based on opcode and ModR/M reg field
private static readonly string[][] FpuMnemonics = new string[8][];
// Two-byte floating-point instructions
private static readonly Dictionary<ushort, string> TwoByteInstructions = new Dictionary<ushort, string>();
/// <summary>
/// Static constructor to initialize the FPU mnemonic tables
/// </summary>
static FloatingPointHandler()
{
InitializeFpuMnemonics();
InitializeTwoByteInstructions();
}
/// <summary>
@ -105,6 +109,17 @@ public class FloatingPointHandler : InstructionHandler
FpuMnemonics[7][7] = "fistp";
}
/// <summary>
/// Initializes the two-byte floating-point instructions
/// </summary>
private static void InitializeTwoByteInstructions()
{
// DF E0 - FNSTSW AX (Store FPU status word to AX without checking for pending unmasked floating-point exceptions)
TwoByteInstructions.Add(0xDFE0, "fnstsw");
// Add other two-byte instructions as needed
}
/// <summary>
/// Initializes a new instance of the FloatingPointHandler class
/// </summary>
@ -141,6 +156,27 @@ public class FloatingPointHandler : InstructionHandler
return false;
}
// Check for two-byte instructions
if (position < Length)
{
// Create a two-byte opcode by combining the primary opcode with the next byte
ushort twoByteOpcode = (ushort)((opcode << 8) | CodeBuffer[position]);
// Check if this is a known two-byte instruction
if (TwoByteInstructions.TryGetValue(twoByteOpcode, out string? mnemonic) && mnemonic != null)
{
instruction.Mnemonic = mnemonic;
// Special handling for specific instructions
if (twoByteOpcode == 0xDFE0) // FNSTSW AX
{
instruction.Operands = "ax";
Decoder.SetPosition(position + 1); // Skip the second byte
return true;
}
}
}
// The opcode index in our tables (0-7 for D8-DF)
int opcodeIndex = opcode - 0xD8;