if (VM.VerifyAssertions) VM.assert(isTwoWayBranch());
if (VM.VerifyAssertions) VM._assert(isTwoWayBranch());
  void flipBranchProbability() {    if (VM.VerifyAssertions) VM.assert(isTwoWayBranch());    setBranchProbability(1.0f-getBranchProbability());  }