private final int localOffset  (int local) { return (stackHeights[biStart] - local)<<LG_WORDSIZE;
private final Offset localOffset  (int local) { return Offset.fromIntZeroExtend((stackHeights[biStart] - local)<<LG_WORDSIZE);
  private final int localOffset  (int local) {    return (stackHeights[biStart] - local)<<LG_WORDSIZE;  }