message: Lift up the unpack op at the beginning of function
diff: @@ -174,7 +174,7 @@ public:
  assert(argpack.hasOneUse());
  auto unpack = cast<stdx::UnpackOp>(*argpack.user_begin());
  // Make a new unpack that also unpacks the exec env
  - builder.setInsertionPoint(unpack.getOperation());
  + builder.setInsertionPointToStart(&func.getBody().front());
  SmallVector<Type, 4> newUnpackTypes(unpack.getResultTypes().begin(),
  unpack.getResultTypes().end());
  newUnpackTypes.insert(newUnpackTypes.begin(), execEnvType);
  