[llvm] AMDGPU: Add tonearest and towardzero roundings for intrinsic llvm.fptrunc.round (PR #104486)

[Changpeng Fang via llvm-commits]

changpeng wrote:


> Yes. You just need an SDNodeXForm to modify the value

What about a rounding mode that is not supported, such as "round.tonearestaway"? 

I am doing like following, but it does not show that the intrinsic can not be selected:

def as_supported_rounding_mode: SDNodeXForm<imm, [{
  int RoundMode = N->getSExtValue();
  if (RoundMode == (int)RoundingMode::TowardZero ||
      RoundMode == (int)RoundingMode::NearestTiesToEven ||
      RoundMode == (int)RoundingMode::TowardPositive ||
      RoundMode == (int)RoundingMode::TowardNegative) {
    unsigned HW_Mode = (RoundMode + 3) % 4;
    return CurDAG->getTargetConstant(HW_Mode, SDLoc(N), MVT::i32);
  }
  return SDValue();
}]>;


https://github.com/llvm/llvm-project/pull/104486