if (VM.VerifyAssertions) VM.assert(x >= 0 && x < (OPT_LEVEL_MASK >>> OPT_LEVEL_SHIFT));
if (VM.VerifyAssertions) VM._assert(x >= 0 && x < (OPT_LEVEL_MASK >>> OPT_LEVEL_SHIFT));
  final void setOptLevel(int x) {    if (VM.VerifyAssertions) VM.assert(x >= 0 && x < (OPT_LEVEL_MASK >>> OPT_LEVEL_SHIFT));    _bits = (_bits & ~OPT_LEVEL_MASK) | (((long)x) << OPT_LEVEL_SHIFT);  }