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;
}