public object TryLookup(CodeContext mode,
ImmutableLegacyPrefixList legacyPrefixes, Xex xex, byte opcode,
out bool hasModRM, out int immediateSizeInBytes)
{
if (xex.OpcodeMap == OpcodeMap.Default && opcode == 0x90)
{
// NOP
hasModRM = false;
immediateSizeInBytes = 0;
return found;
}
else if (xex.OpcodeMap == OpcodeMap.Escape0F && opcode == 0x1F)
{
// 3+ byte nop form
hasModRM = true;
immediateSizeInBytes = 0;
return found;
}
else if (xex.OpcodeMap == OpcodeMap.Default && (opcode & 0xF8) == 0xB0)
{
// MOV x8, imm8
hasModRM = false;
immediateSizeInBytes = 1;
return found;
}
else if (xex.OpcodeMap == OpcodeMap.Default && (opcode & 0xF8) == 0xB8)
{
// Mov r(16|32|64), imm(16|32|64)
OperandSize operandSize;
if (mode == CodeContext.SixtyFourBit)
operandSize = xex.OperandSize64 ? OperandSize.Qword : OperandSize.Dword;
else
operandSize = mode.GetDefaultOperandSize().OverrideWordDword(
legacyPrefixes.HasOperandSizeOverride);
hasModRM = false;
immediateSizeInBytes = operandSize.InBytes();
return found;
}
else if (xex.OpcodeMap == OpcodeMap.Escape0F
&& (xex.SimdPrefix ?? legacyPrefixes.GetSimdPrefix(xex.OpcodeMap)) == SimdPrefix._66
&& opcode == 0x58)
{
hasModRM = true;
immediateSizeInBytes = 0;
return found;
}
else
{
hasModRM = false;
immediateSizeInBytes = 0;
return null;
}
}
object IInstructionDecoderLookup.TryLookup(
CodeContext mode, ImmutableLegacyPrefixList legacyPrefixes,
Xex xex, byte opcode, out bool hasModRM, out int immediateSizeInBytes)
{
var operandSize = mode.GetEffectiveOperandSize(legacyPrefixes, xex);
var addressSize = mode.GetEffectiveAddressSize(legacyPrefixes);
InstructionDefinition bestMatch = null;
int bestOperandSizeMatchLevel = -1;
var lookupKey = OpcodeEnum.MakeLookupKey(legacyPrefixes.GetSimdPrefix(xex.OpcodeMap), xex.OpcodeMap, opcode);
foreach (var instruction in byOpcodeKey[lookupKey])
{
var encoding = instruction.Encoding;
// Ensure we match the RexW requirements
if ((encoding & InstructionEncoding.RexW_Mask) == InstructionEncoding.RexW_Fixed
&& xex.OperandSize64 != ((instruction.Opcode & Opcode.RexW) != 0))
{
continue;
}
// Ensure we match the opcode
if ((opcode & encoding.GetOpcodeMainByteFixedMask()) != instruction.Opcode.GetMainByte())
continue;
// Record the candidate, favoring more specific operand size matches
var operandSizeMatchLevel = GetOperandSizeMatchLevel(encoding, operandSize);
if (operandSizeMatchLevel > bestOperandSizeMatchLevel)
{
bestMatch = instruction;
bestOperandSizeMatchLevel = operandSizeMatchLevel;
}
}
if (bestMatch == null)
{
hasModRM = false;
immediateSizeInBytes = 0;
return null;
}
hasModRM = bestMatch.Encoding.HasModRM();
immediateSizeInBytes = bestMatch.Encoding.GetImmediatesSizeInBytes(operandSize, addressSize);
return bestMatch;
}
