Method FIST

FEXCore/Source/Interface/Core/OpcodeDispatcher/X87.cpp:152–186

Store integer to memory (possibly with truncation)

// Store integer to memory (possibly with truncation)
void OpDispatchBuilder::FIST(OpcodeArgs, bool Truncate) {
  const auto Size = OpSizeFromSrc(Op);
  Ref Data = _ReadStackValue(0);

  // For 16-bit integers, we need to manually check for overflow
  // since _F80CVTInt doesn't handle 16-bit overflow detection properly
  if (Size == OpSize::i16Bit) {
    // Extract the 80-bit float value to check for special cases
    // Get the upper 64 bits which contain sign and exponent and then the exponent from upper.
    Ref Upper = _VExtractToGPR(OpSize::i128Bit, OpSize::i64Bit, Data, 1);
    Ref Exponent = _And(OpSize::i64Bit, Upper, Constant(0x7fff));

    // Check for NaN/Infinity: exponent = 0x7fff
    SaveNZCV();
    _TestNZ(OpSize::i64Bit, Exponent, Constant(0x7fff));
    Ref IsSpecial = _NZCVSelect01({COND_EQ});

    // For overflow detection, check if exponent indicates a value >= 2^15
    // Biased exponent for 2^15 is 0x3fff + 15 = 0x400e
    SubWithFlags(OpSize::i64Bit, Exponent, 0x400e);
    Ref IsOverflow = _NZCVSelect01({COND_UGE});

    // Set Invalid Operation flag if overflow or special value
    Ref InvalidFlag = _Or(OpSize::i64Bit, IsSpecial, IsOverflow);
    SetRFLAG<FEXCore::X86State::X87FLAG_IE_LOC>(InvalidFlag);
  }

  Data = _F80CVTInt(Size, Data, Truncate);

  StoreResult_WithOpSize(GPRClass, Op, Op->Dest, Data, Size, OpSize::i8Bit);

  if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
    _PopStackDestroy();
  }
}

void OpDispatchBuilder::FADD(OpcodeArgs, IR::OpSize Width, bool Integer, OpDispatchBuilder::OpResult ResInST0) {
  if (Op->Src[0].IsNone()) { // Implicit argument case