message: fix crash in parse_rounding
diff: @@ -30,7 +30,7 @@ namespace {
  FpRoundingMode parse_rounding(llvm::Instruction &i) {
  auto *fp = dyn_cast<llvm::ConstrainedFPIntrinsic>(&i);
  - if (!fp)
  + if (!fp || !fp->getRoundingMode().hasValue())
  return {};
  switch (fp->getRoundingMode().getValue()) {
  case llvm::RoundingMode::Dynamic: return FpRoundingMode::Dynamic;
  