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Added support for 0x83 opcode (Group 1 operations with sign-extended immediate)

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bird_egop 2025-04-12 19:04:43 +03:00
parent 1a76bb4e77
commit 2e6e133159
1 changed files with 41 additions and 0 deletions
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41
X86Disassembler/X86/InstructionDecoder.cs
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@ -94,6 +94,11 @@ public class InstructionDecoder
OneByteOpcodes[0xDE] = "fiadd"; // Various FP instructions based on ModR/M
OneByteOpcodes[0xDF] = "fistp"; // Various FP instructions based on ModR/M
// Group 1 instructions (ADD, OR, ADC, SBB, AND, SUB, XOR, CMP)
OneByteOpcodes[0x80] = "group1b";
OneByteOpcodes[0x81] = "group1d";
OneByteOpcodes[0x83] = "group1s"; // Sign-extended immediate
// Data transfer instructions
for (int i = 0x88; i <= 0x8B; i++)
{
@ -441,6 +446,42 @@ public class InstructionDecoder
}
break;
case 0x83: // Group 1 with sign-extended immediate byte
if (_position < _length)
{
byte modRM = _codeBuffer[_position++];
byte mod = (byte)((modRM & MODRM_MOD_MASK) >> 6);
byte reg = (byte)((modRM & MODRM_REG_MASK) >> 3); // This is the operation type
byte rm = (byte)(modRM & MODRM_RM_MASK);
// Determine the operation based on reg field
string[] group1Ops = { "add", "or", "adc", "sbb", "and", "sub", "xor", "cmp" };
mnemonic = group1Ops[reg];
// Decode the destination operand
string destOperand;
if (mod == 3) // Register operand
{
destOperand = RegisterNames32[rm];
}
else // Memory operand
{
destOperand = DecodeModRM(mod, rm, false);
}
// Read the immediate byte
if (_position < _length)
{
sbyte imm8 = (sbyte)_codeBuffer[_position++];
operands = $"{destOperand}, 0x{imm8:X2}";
}
else
{
operands = $"{destOperand}, ???";
}
}
break;
default:
// Handle register-based instructions
if (opcode >= 0x40 && opcode <= 0x47) // INC r32